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The impact of surgical day care on hospital inpatient utilization in a paediatric population Elo, Jyrki A. I. 1987

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IMPACT OF SURGICAL DAY CARE ON HOSPITAL INPATIENT UTILIZATION IN A PAEDIATRIC POPULATION By JYRKI A.I. ELO M.D., The U n i v e r s i t y o f Kuopio, 1980 A THESIS SUBMITTED IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE HEALTH SERVICES PLANNING AND ADMINISTRATION i n THE FACULTY OF GRADUATE STUDIES Department o f H e a l t h Care and Epidemiology We accept t h i s t h e s i s as conforming t o r e q u i r e d s t a n d a r d THE UNIVERSITY OF BRITISH COLUMBIA November 1987 © J y r k i A.I. E l o , 1987 In presenting this thesis in partial fulfilment of the requirements for an advanced degree at the University of British Columbia, I agree that the Library shall make it freely available for reference and study. I further agree that permission for extensive copying of this thesis for scholarly purposes may be granted by the head of my department or by his or her representatives. It is understood that copying or publication of this thesis for financial gain shall not be allowed without my written permission. Department of Hea l th Care and Epidemio logy The University of British Columbia 1956 Main Mall Vancouver, Canada V6T 1Y3 Date November 23 , 1987 DE-6(3/81) i i ABSTRACT Day c a r e s u r g i c a l s e r v i c e s have been marketed as a c o s t s a v i n g a l t e r n a t i v e f o r i n p a t i e n t c a r e . There i s e v i d e n c e t h a t the c o s t p e r ep i sode of day c a r e su r ge ry i s 50-70 p e r c e n t l e s s than a comparable ep i sode i n an i n p a t i e n t ward. In a d d i t i o n , a v o i d i n g h o s p i t a l i z a t i o n has p a r t i c u l a r r e l e v a n c e f o r p a e d i a t r i c s , because o f the u n d e s i r a b l e e f f e c t s of h o s p i t a l s t a y on c h i l d r e n . However, both c o s t s av ing s and the q u a l i t y - b a s e d need t o dec rease h o s p i t a l i z a t i o n s o f c h i l d r e n w i l l be f u l l f i l l e d o n l y i f each p a t i e n t c a red f o r i n a day c a r e s u r g e r y u n i t would o therw i se have been an i n p a t i e n t and the bed v a c a t e d by day ca re su r ge ry use would not be f i l l e d i n by o t h e r p a t i e n t s . In a p r e v i o u s B.C. s tudy based on the t o t a l p o p u l a t i o n a s i g n i f i c a n t component of day c a r e su r ge ry was found t o augment t o t a l u t i l i z a t i o n , sugges t ing g e n e r a t i o n of s u r g i c a l a c t i v i t y r a t h e r than s u b s t i t u t i o n . The p r e s e n t s tudy was de s i gned to examine the s u b s t i t u t i o n / g e n e r a t i o n i s s u e i n the p a e d i a t r i c (0-14 y e a r s ) p o p u l a t i o n , both because e x p e r t s q u e s t i o n e d the g e n e r a l i z a b i l i t y o f the f i n d i n g s t o the p a e d i a t r i c p o p u l a t i o n , and because of the d ramat i c r e d u c t i o n i n p a e d i a t r i c u t i l i z a t i o n i n Canada d u r i n g the p e r i o d s i n c e the mid-1960s. i i i The c o n t e n t i o n was t h a t the i n t r o d u c t i o n of day care surgery may have been an important f a c t o r i n t h i s downtrend. The r e l a t i o n s h i p between p a e d i a t r i c day care s u r g e r y use and h o s p i t a l i n p a t i e n t u t i l i z a t i o n was analyzed i n B.C. i n each of the years 1968-1976 and 1981/82-1982/83 and u s i n g a time s e r i e s / c r o s s - s e c t i o n study d e s i g n . The data frame c o n s i s t e d of a l l B.C. s c h o o l d i s t r i c t s , i n each of the study y e a r s , y i e l d i n g 825 data p o i n t s . Using a m u l t i v a r i a t e r e g r e s s i o n a n a l y s i s , i t was p o s s i b l e t o estimate what h o s p i t a l u t i l i z a t i o n p a t t e r n s would have been i n the absence of day care s u r g e r y c a p a c i t y , and hence i s o l a t e e s t i m a t e s of the net impact of day care surgery on p a e d i a t r i c i n p a t i e n t use. F i n d i n g s on the r e l a t i o n s h i p between day care s u r g e r y use and p a e d i a t r i c m e d i c a l / s u r g i c a l and s u r g i c a l i n p a t i e n t u t i l i z a t i o n s t r o n g l y support the view t h a t p a e d i a t r i c day care s u r g e r y has been l a r g e l y an add-on t o the t o t a l h o s p i t a l care system. S t a t i s t i c a l l y s i g n i f i c a n t s u b s t i t u t i o n e f f e c t was r e v e a l e d o n l y f o r the most narrowly d e f i n e d i n p a t i e n t s u r gery c a t e g o r y which more c l o s e l y resembled day care surgery-type cases, a f t e r c o n t r o l l i n g f o r p o t e n t i a l confounding e f f e c t s of age and sex, p a e d i a t r i c bed c a p a c i t y , d i f f e r e n t socioeconomic c h a r a c t e r i s t i c s and time- and d i s t r i c t - s p e c i f i c f a c t o r s . Even here, l e s s than 10 p e r c e n t of day care s u r g e r y r e p r e s e n t e d s u b s t i t u t i o n f o r i n p a t i e n t surgery and over 90 p e r c e n t appeared t o be g e n e r a t i o n of new a c t i v i t y t o the h o s p i t a l i v system as a whole. Furthermore, p a e d i a t r i c beds which were "saved" by day care surgery use were f i l l e d w i t h i n c r e a s e d u t i l i z a t i o n by non-day care surgery e l i g i b l e s u r g i c a l p a t i e n t s and by med i c a l cases. The main d r i v i n g f o r c e behind h o s p i t a l u t i l i z a t i o n i n the 0-14 year age group was p a e d i a t r i c bed a v a i l a b i l i t y even a f t e r s t a n d a r d i z a t i o n f o r age, sex, p h y s i c i a n s t o c k , measures of socioeconomic s t a t u s , and ot h e r d i s t r i c t - and y e a r - s p e c i f i c e f f e c t s . A c c o r d i n g t o t h i s study p a e d i a t r i c day care s u r g e r y has not been a c o s t s a v i n g a l t e r n a t i v e f o r i n p a t i e n t c a r e i n B.C. i n 1968-1982/83. N e i t h e r has i t reduced o v e r a l l h o s p i t a l i z a t i o n s i n the p a e d i a t r i c p o p u l a t i o n . V TABLE OF CONTENTS Page ABSTRACT i i L IST OF TABLES i x L IST OF FIGURES x i i ACKNOWLEDGEMENT x i i i 1. INTRODUCTION 1 1.1. H e a l t h s e r v i c e s r e s e a r c h and p o l i c y - m a k i n g . . . 1 1.2. Background o f the s tudy 2 1.3. Purpose of the s tudy 9 1.4. Study o b j e c t i v e s 10 1.5. U n d e r l y i n g t h e o r i e s and s tudy hypotheses 11 1.6. T h e s i s format 15 2. LITERATURE REVIEW 17 2.1. Why not i n p a t i e n t care? 17 2.2. Day c a r e su r ge ry - a l t e r n a t i v e f o r i n p a t i e n t c a re 25 2 .2 .1 . D e f i n i t i o n 25 2 .2 .2 . A b r i e f h i s t o r y of p a e d i a t r i c day c a r e su r ge ry 28 2 .2 .3 . S a f e t y o f p a e d i a t r i c day c a r e s u r g e r y . 29 2 .2 .4 . P a e d i a t r i c day c a r e s u r g e r y l o a d and p rocedures 32 2.3. E s t i amtes of p o t e n t i a l c o s t sav ings r e a l t e d t o day c a r e su r ge ry 33 v i page 2.4. Response of i n p a t i e n t u t i l i z a t i o n t o day c a r e s u r g e r y 39 2.5. The r o l e o f i n a p t i e n t bed supp l y - Roemer's Law 43 2 .5 .1 . E v o l u t i o n o f Roemer's Law 43 2 .5 .2 . Ques t i on o f c a u s a l i t y 46 2 .5 .3 . The Roemer e f f e c t i n p a e d i a t r i c p o p u l a t i o n s 51 2.6. Other f a c t o r s i n p a e d i a t r i c i n p a t i e n t use . . . . 55 2 .6 .1 . P r e v a l e n c e , i n c i d e n c e and t ype of i l l n e s s 56 2 .6 .2 . Demographic f a c t o r s 59 2 .6 .3 . Soc ioeconomic f a c t o r s 61 2 .6 .4 . M e d i c a l c a re a v a i l a b i l i t y 63 2.7. Summary of l i t e r a t u r e rev iew 68 3. DATA SOURCES AND METHODS 71 3 .1 . Study u n i t and r e s e a r c h d e s i g n 71 3.2. Dependent v a r i a b l e - p a e d i a t r i c i n p a t i e n t h o s p i t a l use pe r c a p i t a 76 3 .2 .1 . E x c l u s i o n s from numerator 76 3 .2 .2 . I n c l u s i o n s i n numerator 81 3 .2 .3 . Measures of the dependent v a r i a b l e numerator 85 3 .2 .4 . Denominator of the dependent v a r i a b l e . 93 3 .2 .5 . Age- sex adjustment o f the dependent v a r i a b l e 93 3.3. Independent v a r i a b l e s 95 3 .3 .1 . Day c a r e su r ge ry a v a i l a b i l i t y (DCS) . . . 95 v i i page 3 .3 .2 . H o s p i t a l bed a v a i l a b i l i t y (BEDS) 97 3 . 3 . 2 . 1 . Adjustment f o r boundary c r o s s i n g (B") 98 3 .3 .2 .2 . Adjustment f o r non-homogeneous p o p u l a t i o n (P~) 104 3 .3 .3 . Number o f p h y s i c i a n s pe r c a p i t a (DOCS) 106 3 .3 .4 . Soc ioeconomic v a r i a b l e s 112 3.4. Data sources 116 3 . 4 . 1 . A d m i s s i o n - s e p a r a t i o n database f o r i n p a t i e n t use 116 3 .4 .2 . A d m i s s i o n - s e p a r a t i o n database f o r day c a r e su r ge ry 117 3 .4 .3 . O u t - o f - p r o v i n c e u t i l i z a t i o n 118 3 .4 .4 . P o p u l a t i o n and soc ioeconomic da ta 118 3 .4 .5 . H o s p i t a l bed c a p a c i t y da ta 121 3.5. S t a t i s t i c a l a n a l y s i s 121 4. RESULTS 127 4 .1 . D e s c r i p t i v e da ta - an overv iew of p a e d i a t r i c u t i l i z a t i o n i n B .C. , 1968-1982/83 127 4 .2 . Day c a r e s u r g e r y a v a i l a b i l i t y and p a e d i a t r i c i n p a t i e n t u t i l i z a t i o n 139 v i i i page 4.3. P a e d i a t r i c bed a v a i l a b i l i t y and i n p a t i e n t u t i l i z a t i o n 149 4.4. A d j u s t i n g f o r the e f f e c t of bed supply 156 4.5. N o n - l i n e a r bed e f f e c t 167 4.6. Confounding f a c t o r s 174 4.6.1. P h y s i c i a n - t o - p o p u l a t i o n r a t i o 175 4.6.2. Socioeconomic v a r i a b l e s 182 4.6.3. Unmeasured confounding f a c t o r s 197 4.7. Roemer's Law and d e c r e a s i n g bed supply 209 5. DISCUSSION 217 6. BIBLIOGRAPHY 231 i x L IST OF TABLES T a b l e page 1 I nc i dence o f I n p a t i e n t and Day Care Su rge ry p e r 1,000 P o p u l a t i o n and Percentage of Day Care Surgery o f T o t a l Surgery i n B.C. by T o t a l and P a e d i a t r i c (0-14 yea r s ) P o p u l a t i o n by Year 3 2 Most Common O p e r a t i v e C a t e g o r i e s i n Day Care Surgery i n the P a e d i a t r i c (0-14 y e a r s ) Age Group i n B.C. i n 1976 and i n 1982/83 34 3 Ten Most Common Day Care Surgery Procedures i n P a e d i a t r i c (0-14) Age Group i n B.C. i n 1976 and 1982/83 35 4 P r o p o r t i o n o f Ou t -o f P r o v i n c e U t i l i z a t i o n of the T o t a l I n - and O u t - P r o v i n c e U t i l i z a t i o n by Schoo l D i s t r i c t i n 1971, 1976 and 1981/82 83 5 N o n - o p e r a t i v e Procedures Exc luded i n T h i s Study by D i f f e r e n t R e v i s i o n s of I n t e r n a t i o n a l C l a s s i f i c a t i o n of D i seases 88 6 Most Common S u r g i c a l Day Care Procedures i n P e a d i a t r i c Age Group i n B.C. i n 1982/83 and T h e i r M u l t i p l i c a t i o n F a c t o r s f o r SURG C Measure 90 7 Number o f A c t u a l and S y n t h e t i c P a e d i a t r i c Beds by Schoo l D i s t r i c t i n B.C. i n 1971, 1976, and 1981/82 101 8 A c t u a l and A d j u s t e d P o p u l a t i o n s f o r 0-14 Age Group by Schoo l D i s t r i c t i n 1971, 1976, and 1981/82 107 9 Means and S tandard D e v i a t i o n s of D i f f e r e n t Measures o f P a e d i a t r i c I n p a t i e n t U t i l i z a t i o n (per 1,000 P o p u l a t i o n ) Over Schoo l D i s t r i c t s by Year . . . 128 10 Means and S tandard D e v i a t i o n s o f DCS and BEDS V a r i a b l e s (per 1,000 P o p u l a t i o n ) Over S choo l D i s t r i c t s by Year 133 X T a b l e page 11 Means and S tandard D e v i a t i o n s o f D i f f e r e n t Measures of P h y s i c i a n A v a i l a b i l i t y pe r 10,000 P o p u l a t i o n (0-14 Years ) Over Schoo l D i s t r i c t s by Year 135 12 Means and S tandard D e v i a t i o n s o f D i f f e r e n t Soc ioeconomic V a r i a b l e s Over Schoo l D i s t r i c t s by Census Year 137 13 C o r r e l a t i o n M a t r i x o f Main Study V a r i a b l e s i n Poo led 1968-1982/83 Dataset 138 14 Schoo l D i s t r i c t MED/SURG and SURG Equat ions w i t h DCS by Year 140 15 Schoo l D i s t r i c t I n p a t i e n t U t i l i z a t i o n Equat ions w i t h DCS i n 1971, 1976, and Poo led 1968-1982/83 Dataset 143 16 Schoo l D i s t r i c t MED/SURG and SURG Equat ions w i t h BEDS by Year 151 17 Schoo l D i s t r i c t I n p a t i e n t H o s p i t a l U t i l i z a t i o n Equat ions w i t h BEDS i n 1971, 1976, and Poo led 1968-1982/83 Dataset 154 18 Schoo l D i s t r i c t I n p a t i e n t H o s p i t a l U t i l i z a t i o n Equat ions w i t h DCS and BEDS V a r i a b l e s by Year . . 158 19 Schoo l D i s t r i c t I n p a t i e n t H o s p i t a l U t i l i z a t i o n Equat ions w i t h DCS and BEDS i n 1971, 1976, 1981/82, Poo led 1968-1976, and Poo led 1968-1982/83 Dataset 162 20 Schoo l D i s t r i c t I n p a t i e n t H o s p i t a l U t i l i z a t i o n Equa t ions w i t h BEDS and BEDSQ i n Poo led 1968-82/83 Dataset 169 21 Schoo l D i s t r i c t I n p a t i e n t H o s p i t a l U t i l i z a t i o n Equat ions w i t h DCS, BEDS and BEDSQ i n 1971, 1976, 1981/82, Poo led 1968-1976, and Poo led 1968-1982/83 Dataset 172 22 Schoo l D i s t r i c t I n p a t i e n t H o s p i t a l U t i l i z a t i o n Equat ions w i t h DCS, BEDS, BEDSQ and DOCS i n 1976, 1981/82 and Poo led 1973-1982/83 Dataset . . 177 x i T a b l e page 23 Schoo l D i s t r i c t I n p a t i e n t H o s p i t a l U t i l i z a t i o n Equat ions w i t h DCS, BEDS, BEDSQ, GP, PAED, SURGEON, ANA and OTHER V a r i a b l e s i n Poo led 1973-1982/83 Dataset 181 24 Schoo l D i s t r i c t I n p a t i e n t H o s p i t a l U t i l i z a t i o n Equat ions w i t h Soc ioeconomic V a r i a b l e s i n 1971, 1981/82 and Poo led 1968-1982/83 Da ta se t 183 25 Schoo l D i s t r i c t I n p a t i e n t H o s p i t a l U t i l i z a t i o n Equat ions w i t h DCS, BEDS, BEDSQ and Soc ioeconomic V a r i a b l e s i n 1971, 1981/82 and Poo led 1968-1982/83 Dataset 189 26 Schoo l D i s t r i c t I n p a t i e n t H o s p i t a l U t i l i z a t i o n Equat ions w i t h DCS, BEDS, BEDSQ and Time and /o r D i s t r i c t Dummies i n Poo led 1968-82/83 Dataset . . 199 27 Schoo l D i s t r i c t I n p a t i e n t H o s p i t a l U t i l i z a t i o n Equat ions w i t h DCS, BEDS, BEDSQ, Soc ioeconomic V a r i a b l e s and Time and D i s t r i c t Dummies i n Poo led 1968-1982/83 Dataset 208 28 Schoo l D i s t r i c t i n p a t i e n t H o s p i t a l U t i l i z a t i o n Equat ions w i t h DCS, BEDS, BEDSQ, BEDSD and BEDSQD i n Poo led 1968-82/83 Dataset 211 x i i L IST OF FIGURES F i g u r e page 1 S choo l d i s t r i c t boundar ie s i n the s tudy 77 2 H y p o t h e t i c a l p l o t o f i n p a t i e n t use a g a i n s t DCS use 123 3 S i m p l i f i e d i l l u s t r a t i o n o f the d i f f e r e n c e s i n r e g r e s s i o n equa t i ons between i n d i v i d u a l y e a r s and the poo led d a t a s e t 144 x i i i ACKNOWLEDGEMENTS The p r e s e n t s tudy i s a component i n a b roader at tempt to examine the economics o f p a e d i a t r i c h o s p i t a l s e r v i c e s i n B.C. , and i t c o n t i n u e s the work i n i t i a t e d by P r o f e s s o r G e o f f r e y C. Robinson and P r o f e s s o r Robert G. Evans. I w i sh t o expres s my deep g r a t i t u d e t o them f o r t h e i r c o n s t r u c t i v e c r i t i c i s m and c o u n s e l i n g d u r i n g the p roces s o f my work and f o r t h e i r u n f a i l i n g i n t e r e s t and t r u s t i n my s tudy . I a l s o w i sh t o thank Dr. M o r r i s L. Ba re r f o r many f r u i t f u l d i s c u s s i o n s , c o n s t r u c t i v e c r i t i c i s m and v a l u a b l e gu idance throughout the p rog re s s of t h i s s tudy . My s i n c e r e thanks a re a l s o due t o Mr. P a t r i c Wong-Fung f o r h i s s k i l f u l a s s i s t a n c e i n p r e p a r i n g the d i f f e r e n t databases f o r the a n a l y s e s . 1 1. INTRODUCTION 1.1. H e a l t h s e r v i c e s r e s e a r c h and p o l i c y - m a k i n g A l though p u b l i c p o l i c i e s a re u s u a l l y a r e s u l t o f a complex p r o c e s s o f b a r g a i n i n g and t i m i n g , i t i s w i d e l y argued (and accepted ) t h a t the i n f o r m a t i o n ga ined from p r o p e r l y - c o n d u c t e d s t u d i e s can h e l p to make s o c i a l p o l i c i e s both more e f f e c t i v e i n a t t a i n i n g the o b j e c t i v e s they were des i gned t o meet, and more e f f i c i e n t i n t h e i r deployment o f human and f i n a n c i a l r e s o u r c e s f o r the achievement of those o b j e c t i v e s (Robertson and Gandy, 1983). In s p i t e of h i gh e x p e c t a t i o n s o f r e s e a r c h e r s a rev iew of the l i t e r a t u r e on r e s e a r c h u t i l i z a t i o n demonstrates t h a t r e s e a r c h has had o n l y a l i m i t e d d i r e c t impact on p o l i c y - m a k i n g (Rubin and R o s e n b l a t t , 1979; Weiss , 1980). From a p o l i c y - m a k e r s p o i n t o f v iew r e s e a r c h i s c o n s i d e r e d a l ong w i t h emot iona l and n o n - q u a n t i f i a b l e f a c t s such as p o l i t i c a l demands, i n t u i t i o n and e x p e r i e n c e i n a p o l i t i c a l p roce s s t h a t i n c l u d e s d e c i s i o n s about p o l i c y and p r a c t i c e (Robertson and Gandy, 1983). T h i s s tudy i s conducted i n a f a i t h t h a t t h e r e i s s t i l l room f o r r a t i o n a l i t y i n p o l i c y - m a k i n g . I see the r o l e of t h i s s tudy as d e s c r i b e d by the "en l i gh tenment " model proposed by Weiss (1977). The most impor tant r o l e f o r r e s e a r c h i n p o l i c y -2 making i s to provide an i n t e l l e c t u a l s e t t i n g of concepts, propositions, orientations, and empirical generalizations that w i l l expand the policy-maker's frame of reference and thus influence p o l i c y decisions. This study t r i e s to shed l i g h t on the p o l i c y to provide paediatric s u r g i c a l services on a day care basis. The key issue i s resource a v a i l a b i l i t y and i t s r e l a t i o n s h i p to hospital u t i l i z a t i o n within the paediatric population. Potential causal associations that w i l l be examined are fundamental i n viewing the operations of paediatric s u r g i c a l services and i n assessing the impact of day care surgery and hospital bed capacity on h o s p i t a l u t i l i z a t i o n i n t h i s population. 1.2. Background of the study Day care s u r g i c a l services have been provided as a hospital insurance benefit i n B r i t i s h Columbia since e a r l y 1968 (Province of B r i t i s h Columbia, 1968). Since then there has been a dramatic expansion i n the performance of s u r g i c a l procedures on a day care basis. The number of day care s u r g i c a l operations per 1000 population has increased from 6.7 i n 1968 to 41.8 i n 1982/83 (Table 1 ) . The expansion of t h i s kind of surgery has also been of s i m i l a r magnitude i n the c h i l d population. In 1968 there were 4.6 operations per 1000 c h i l d r e n of 0-14 years and i n 1982/83 the rate was 22 .8 . /Among children, day care surgery accounts for almost half of the 3 T a b l e 1 I n c i dence o f I n p a t i e n t and Day Care Su r ge ry p e r 1,000 p o p u l a t i o n and Percentage o f Day Care Surgery o f T o t a l Su rgery i n B.C. by T o t a l and P a e d i a t r i c (0-14 y e a r s ) P o p u l a t i o n by Year T o t a l P o p u l a t i o n Pflftdj flt.ri C P o p u l a t i o n Year I n p a t i e n t Day Care I n p a t i e n t Day Care Inc. Inc. % Inc. Inc. % 1968 83 .77 6 .73 7 .44 60 .98 4 .60 7 .01 1969 80 .93 10 .43 11 .42 53 .17 6 .87 11 .44 1970 83 .74 15 .16 15 .33 52 .38 10 .59 16 .82 1971 83 .96 18 .12 17 .75 48 .64 11 .85 19 .59 1972 83 .13 19 .68 19 .14 45 .39 12 .47 21 .55 1973 82 .41 21 .69 20 .84 43 .94 13 .89 24 .02 1974 82 .85 23 .51 22 .10 42 .42 13 .95 24 .75 1975 80 .49 25 .30 23 .92 39 .88 14 .69 26 .92 1976 78 .29 26 .62 25 .37 37 .16 15 .21 29 .04 % Change between -6 .54 295 .54 -39 .06 230 .65 1968-76 1981/82 77 .32 38 .29 33 .12 30 .11 22 .30 42 .55 1982/83 74 .66 41 .75 35 .86 26 .58 22 .80 46 . 17 % Change between •10 .88 520 .36 -56 .41 395 .65 1968-82/83 S o u r c e s : NUMERATOR DATA: T o t a l p o p u l a t i o n : P r o v i n c e of B r i t i s h Co lumb ia : Report on day ca re su r ge ry 1982/83, B r i t i s h Co lumbia . M i n i s t r y of H e a l t h , Research D i v i s i o n , H o s p i t a l Programs, V i c t o r i a , n . d . 1983; and unpub l i s hed d a t a , B.C. M i n i s t r y of H e a l t h , H o s p i t a l Programs. P a e d i a t r i c p o p u l a t i o n : Robinson CG, C l a r k e HF ( ed s ) : The H o s p i t a l Care of C h i l d r e n . A r ev i ew of contemporary i s s u e s . Oxford U n i v e r s i t y P r e s s , New York 1980; and unpub l i s hed d a t a , B.C. M i n i s t r y of H e a l t h , H o s p i t a l Programs. DENOMINATOR DATA: I n t r a - and e x t r a p o l a t e d from the 1961, 1971 and 1981 Census d a t a . 4 o v e r a l l s u r g i c a l l o a d i n 1982/83, i n c o n t r a s t t o j u s t over one t h i r d i n the t o t a l p o p u l a t i o n (Tab le 1 ) . There a re s e v e r a l p o s s i b l e reasons why day c a r e s u r g e r y has become so p o p u l a r and i s i n c r e a s i n g i t s p o r t i o n of t o t a l s u r g e r y . One of the main arguments t o suppor t day c a r e s u r g e r y has been t h a t i t r e p r e s e n t s a l e s s expens i ve a l t e r n a t i v e to i n p a t i e n t h o s p i t a l c a r e . P o t e n t i a l t o t a l s av ing s pe r ep i sode c o u l d be 50-70 p e r c e n t (Evans e t a 1., 1978). The development of o u t p a t i e n t s e r v i c e s t o e l i m i n a t e unneces sa ry i n p a t i e n t admiss ions was recommended by the H a l l Commission as one of the p r i n c i p a l means of l o w e r i n g o r , c o n t r o l l i n g h e a l t h c a re and p a r t i c u l a r l y h o s p i t a l c o s t s (Canada, 1964). In a d d i t i o n , a v o i d i n g h o s p i t a l i z a t i o n has p a r t i c u l a r r e l e v a n c e f o r p a e d i a t r i c s , because o f the u n d e s i r a b l e e f f e c t s of h o s p i t a l s t ay s on c h i l d r e n (Vernon e_t a 1 . , 1965; Rober t son , 1970). I t i s these two reasons t h a t have appea led to p o l i c y - m a k e r s the most i n g e t t i n g t h e i r suppor t f o r expanding p a e d i a t r i c day ca re s u r g i c a l s e r v i c e s . A l though h e a l t h p r o f e s s i o n a l s have a l s o emphasized the c o s t s a v i n g a spec t s o f day ca re su r ge ry programs, t h e i r i n t e r e s t i n t h i s t ype o f t rea tment may a l s o stem from o t h e r grounds. In the 1940s and the 1950s the H o s p i t a l C o n s t r u c t i o n Grant Scheme meant i n c r e a s i n g numbers of h o s p i t a l beds i n Canada and h e a l t h p r o f e s s i o n a l s ' p r e f e r e n c e was f o r i n p a t i e n t c a r e . In an env i ronment o f a s t a b l e o r d e c r e a s i n g number of h o s p i t a l beds and an i n c r e a s i n g number of p h y s i c i a n s , as i n the 1970s and, 5 e s p e c i a l l y , i n the 1980s, day care surgery c o u l d p r o v i d e a way t o circumvent p e r c e i v e d f a c i l i t y c o n s t r a i n t s . Both c o s t savings and the q u a l i t y - b a s e d need t o decrease h o s p i t a l i z a t i o n s of c h i l d r e n w i l l be f u l l f i l l e d o n l y i f each p a t i e n t cared f o r i n a day care surgery u n i t would otherwise have been an i n p a t i e n t and the bed vacated by day care surgery use would not be f i l l e d i n by o t h e r p a t i e n t s . T h i s s u b s t i t u t i o n e f f e c t has been assumed r a t h e r than a c t u a l l y observed. There are b a s i c a l l y t h r e e t h e o r e t i c a l p o s s i b i l i t i e s f o r the r e l a t i o n s h i p between day care s u r g e r y use and i n p a t i e n t u t i l i z a t i o n : 1) S t r a i ght s n h s t i t u t i on. Each day care s u r g e r y case s u b s t i t u t e s f o r one i n p a t i e n t admission and v a c a t e d i n p a t i e n t beds are not f i l l e d i n by o t h e r p a t i e n t s . 2) S t r a i g h t add-on. Day care surgery use does not a f f e c t i n p a t i e n t admissions a t a l l and no beds are vacated. Each day care surgery case r e p r e s e n t s an episode of new p a e d i a t r i c surgery. 6 3) Substitution w i th f i l l in of vara tad beds. Each day ca re su r ge ry case s u b s t i t u t e s f o r one i n p a t i e n t adm i s s i on , but vaca ted beds a re f i l l e d i n by o t h e r p a t i e n t s ( e . g . , new m e d i c a l o r non-DCS e l i g i b l e s u r g i c a l c a s e s ) . Each of these p o s s i b i l i t i e s c o u l d e x i s t a l one o r i n d i f f e r e n t comb ina t i on s . Fo r example, one t h i r d o f day ca re s u r g e r y c o u l d be s t r a i g h t add-on (no s u b s t i t u t i o n a t a l l ) , one t h i r d c o u l d be s t r a i g h t s u b s t i t u t i o n ( s u b s t i t u t i o n w i t h no f i l l i n of v a c a t e d beds w i t h o t h e r p a t i e n t s ) , and one t h i r d c o u l d l e a d t o s u b s t i t u t i o n w i t h f i l l i n of v a c a t e d beds . Thus, two t h i r d s of day c a r e su r ge ry would r e p r e s e n t g e n e r a t i o n of new a c t i v i t y f o r the h o s p i t a l system as a whole and o n l y one t h i r d would reduce i n p a t i e n t u t i l i z a t i o n . On ly the s t r a i g h t s u b s t i t u t i o n would f u l l y meet the e x p e c t a t i o n s a s s o c i a t e d w i th the i n t r o d u c t i o n of day c a r e su r ge ry . In the case of s t r a i g h t add-on o r s u b s t i t u t i o n w i t h f i l l i n o f v a c a t e d beds , t h e r e i s no net r e d u c t i o n i n p a e d i a t r i c h o s p i t a l i z a t i o n s , but the t o t a l number of c h i l d r e n ' s h o s p i t a l c o n t a c t s w i l l i n c r e a s e . A r e c e n t s tudy has shown t h a t the assumpt ion of p e r f e c t s u b s t i t u t i o n i s not v a l i d f o r the o v e r a l l p o p u l a t i o n i n B.C. (Evans e t a l . , 1983). T h i r t y t o f o r t y p e r c e n t o f day ca re s u r g e r y was found t o r e p r e s e n t s u b s t i t u t i o n f o r i n p a t i e n t c a r e , but 60-70 p e r c e n t was g e n e r a t i o n of new a c t i v i t y f o r the h o s p i t a l system as a whole and, t h u s , r e p r e s e n t e d add-on c o s t s . The g e n e r a t i o n of new h o s p i t a l u t i l i z a t i o n was a r e s u l t 7 of f i l l i n o f beds , which were saved by day c a r e s u r g e r y use , by non-DCS e l i g i b l e p a t i e n t s , p a r t i c u l a r l y m e d i c a l c a s e s . The c a u s a l p o s i t i v e e f f e c t of bed a v a i l a b i l i t y was the major de te rminant of i n p a t i e n t u t i l i z a t i o n . But do r e s u l t s from the t o t a l p o p u l a t i o n app l y t o c h i l d r e n as w e l l ? A d e c l i n e i n h o s p i t a l i n p a t i e n t u t i l i z a t i o n i n the 0-14 y e a r p o p u l a t i o n s i n c e the 1960s (Sheps, 1980) and the u n d e s i r a b l e consequences of h o s p i t a l i z a t i o n which have l e d pa ren t s t o seek a c t i v e l y a l t e r n a t i v e arrangements t o t r a d i t i o n a l i n p a t i e n t c a r e (Shah e t a l . , 1972), a t l e a s t o f f e r the p o s s i b i l i t y t h a t something d i f f e r e n t may have been go ing on i n p a e d i a t r i c s . P r a c t i t i o n e r s i n the f i e l d of p a e d i a t r i c s c l a i m t h a t 1) c h i l d r e n ' s h e a l t h c a re i s d i f f e r e n t from a d u l t c a r e i n the sense t h a t day ca re s u r g e r y does s u b s t i t u t e f o r i n p a t i e n t c a r e t o a major e x t e n t , and t h a t 2) h o s p i t a l bed a v a i l a b i l i t y does not p l a y a major r o l e i n c h i l d r e n ' s h o s p i t a l u t i l i z a t i o n . To my knowledge, t h e r e have not been s t u d i e s p r e v i o u s l y t h a t have addres sed the f i r s t i s s u e i n a c h i l d p o p u l a t i o n . Repor t s on the second a re s c a r c e and based on c r o s s - s e c t i o n a l da ta (Connell et a l . f 1981). 8 From a p o l i c y p e r s p e c t i v e , the i s s u e o f s u b s t i t u t i o n f o r ve r su s g e n e r a t i o n of h o s p i t a l a c t i v i t y i s o f c e n t r a l importance i n d e c i d i n g on f u t u r e p o l i c i e s c o n c e r n i n g a l t e r n a t i v e s t o i n p a t i e n t c a r e . I f day ca re s u r g e r y has c l e a r l y s u b s t i t u t e d f o r i n p a t i e n t c a re and caused a dec rea se i n p a e d i a t r i c h o s p i t a l i z a t i o n , then t h e r e a re both s t r o n g economic and p s y c h o l o g i c a l arguments t o suppor t a p a e d i a t r i c day c a r e s u r g e r y program. On the o t h e r hand, i f the dec rea se i n p a e d i a t r i c h o s p i t a l i z a t i o n i s due t o reasons o t h e r than day c a r e s u r g e r y , t h a t d e c l i n e may mask a g e n e r a t i o n e f f e c t . The o v e r a l l volume of h o s p i t a l use may have i n c r e a s e d , o r d e c l i n e d l e s s than i t might have i n the absence o f day ca re s u r g i c a l f a c i l i t i e s . I f the l a t t e r i s the c a se , the p a e d i a t r i c day c a r e s u r g e r y program cannot be marketed as a c o s t s a v i n g a l t e r n a t i v e u n l e s s i t i s accompanied by a s imu l taneous adjustment of i n p a t i e n t f a c i l i t i e s . The s tudy by Evans e t a l . (1983) on the impact of day ca re s u r g e r y on i n p a t i e n t u t i l i z a t i o n i n the t o t a l p o p u l a t i o n i n B.C. covered the year s 1968-1976 - a p e r i o d of s teady i n c r e a s e i n bed s u p p l y . Fo r reasons o t h e r than day ca re s u r g e r y , a downs i z i ng of i n p a t i e n t f a c i l i t i e s has taken p l a c e i n B.C. , but m a i n l y a f t e r the y e a r 1976. The p a e d i a t r i c bed t o p o p u l a t i o n r a t i o has d e c l i n e d s i n c e 1975, but the main r a t i o n i n g o f both a d u l t and p a e d i a t r i c beds i n the P r o v i n c e took p l a c e i n the e a r l y 1980s. No p r e v i o u s s t u d i e s have examined the e f f e c t of day ca re su r ge ry on i n p a t i e n t c a re 9 d u r i n g a p e r i o d of d e c r e a s i n g bed s u p p l y . A l s o , most o f the r e p o r t e d s t u d i e s on the bed a v a i l a b i l i t y e f f e c t on h o s p i t a l u t i l i z a t i o n have been conducted d u r i n g p e r i o d s of i n c r e a s i n g o r s teady bed t o p o p u l a t i o n r a t i o s . Would the e f f e c t of bed a v a i l a b i l i t y and the e f f e c t of day c a r e s u r g e r y on i n p a t i e n t u t i l i z a t i o n be d i f f e r e n t i n a p o l i c y environment of d e c r e a s i n g h o s p i t a l r e s o u r c e s ? The answer t o t h i s q u e s t i o n i s o f utmost impor tance i n t r a n s l a t i n g the r e s u l t s of h o s p i t a l u t i l i z a t i o n r e s e a r c h i n t o p o l i c y . 1.3. Purpose o f t h e s tudy In s p i t e o f the d e c l i n i n g p a e d i a t r i c i n p a t i e n t u t i l i z a t i o n t h a t has t aken p l a c e s i m u l t a n e o u s l y w i t h the i n c r e a s e i n day c a r e s u r g e r y a c t i v i t y i n B.C. , t h e r e i s no c l e a r ev i dence t h a t the i n t r o d u c t i o n of day ca re su r ge ry has a c t u a l l y caused p a r t o r a l l of t h i s d e c l i n e . The purpose of t h i s s tudy i s t o a n a l y z e the r e l a t i o n s h i p between day ca re s u r g e r y and i n p a t i e n t u t i l i z a t i o n i n the p a e d i a t r i c p o p u l a t i o n i n B.C. i n 1968-1976 and 1981/82-1982/83 i n o r d e r t o p r o v i d e h e a l t h c a re p l a n n e r s and p o l i c y - m a k e r s i n f o r m a t i o n f o r f u r t h e r d e c i s i o n making c o n c e r n i n g p a e d i a t r i c h o s p i t a l s e r v i c e s . More s p e c i f i c a l l y , t h i s s tudy t r i e s t o answer the f o l l o w i n g q u e s t i o n s : 10 1) Is the i n c r e a s i n g a v a i l a b i l i t y of day care s u r g e r y c a u s a l l y r e l a t e d t o the decrease i n p a e d i a t r i c i n p a t i e n t u t i l i z a t i o n ? 2) Does p a e d i a t r i c i n p a t i e n t bed a v a i l a b i l i t y p l a y a major c a u s a l r o l e i n determining the l e v e l of p a e d i a t r i c i n p a t i e n t u t i l i z a t i o n ? 3) Does p a e d i a t r i c h o s p i t a l u t i l i z a t i o n respond d i f f e r e n t l y t o r e s o u r c e a v a i l a b i l i t y than h o s p i t a l u t i l i z a t i o n of the t o t a l p o p u l a t i o n ? 4) Would the impact of day care s u r g e r y and h o s p i t a l bed a v a i l a b i l i t y on p a e d i a t r i c i n p a t i e n t u t i l i z a t i o n be d i f f e r e n t i n a p o l i c y environment of d e c r e a s i n g h o s p i t a l f a c i l i t i e s than i n an environment of no such c o n s t r a i n t s ? 1.4. S tudy o b j e c t i v e s The o b j e c t i v e s of t h i s study are 1) t o assess the extent t o which day care s u r g e r y has an independent and s i g n i f i c a n t e f f e c t on p a e d i a t r i c i n p a t i e n t u t i l i z a t i o n when o t h e r f a c t o r s which may have an impact on p a e d i a t r i c h o s p i t a l u t i l i z a t i o n have been c o n t r o l l e d . 11 2) t o a s ses s the e x t e n t t o which h o s p i t a l bed a v a i l a b i l i t y has an independent e f f e c t on p a e d i a t r i c i n p a t i e n t u t i l i z a t i o n , o t h e r t h i n g s b e i n g e q u a l . 3) t o a s ses s the impact of a r e s t r a i n i n g p o l i c y environment on the r e l a t i o n s h i p between day ca re s u r g e r y a v a i l a b i l i t y , h o s p i t a l bed a v a i l a b i l i t y and p a e d i a t r i c i n p a t i e n t u t i l i z a t i o n . 1.5. U n d e r l y i n g t h e o r i e s and s tudy hypotheses Evans e t a l . (1983) have p re sen ted a s i m p l i f i e d t h e o r e t i c a l framework on the r e l a t i o n s h i p between day c a r e s u r g e r y and i n p a t i e n t u t i l i z a t i o n . In t h i s framework the impact of day c a r e s u r g e r y on h o s p i t a l i n p a t i e n t u t i l i z a t i o n can be viewed i n two d i f f e r e n t ways. A c c o r d i n g to a "med i ca l needs" model o f h o s p i t a l u t i l i z a t i o n , each c h i l d ca red f o r by a day ca re s u r g e r y u n i t , i n the absence of o v e r a l l c a p a c i t y c o n s t r a i n t s , i s a c h i l d who would o therw i se have been an i n p a t i e n t . Needs f o r c a re a r e i n t e r p r e t e d and conver ted i n t o h o s p i t a l u t i l i z a t i o n by p h y s i c i a n s o r o t h e r h e a l t h p r o f e s s i o n a l s , i n d e p e n d e n t l y of the c a p a c i t y of the h o s p i t a l o r m e d i c a l ca re system. Un les s t h e r e a r e "unmet needs" due t o i n s u f f i c i e n t i n p a t i e n t c a p a c i t y , e v e r y i n c r e a s e i n day c a r e s u r g e r y use shou ld be one f o r one s u b s t i t u t i o n f o r i n p a t i e n t c a r e . Whi le o v e r - u t i l i z a t i o n , u t i l i z a t i o n exceed ing needs , c o u l d i n p r i n c i p l e o c c u r i n t h i s model , i t i s r u l e d out i n p r a c t i c e by 12 the assumpt ions t h a t p r o v i d e r s ' d e c i s i o n s c o n t r o l use and t h a t p r o v i d e r s respond o n l y t o needs ( Evans, 1984). A c c o r d i n g to a "snppTy" model , p r o f e s s i o n a l p e r c e p t i o n s o f need and d e c i s i o n s as t o a p p r o p r i a t e use a r e themse lves i n f l u e n c e d by the c a p a c i t y a v a i l a b l e . An i n c r e a s e i n h o s p i t a l bed s u p p l y w i l l i n c r e a s e the h o s p i t a l u t i l i z a t i o n i n the p o p u l a t i o n - a phenomenon t h a t i s o f t e n c a l l e d Roemer 's Law (Roemer and S h a i n , 1959; Roemer, 1961). I f h o s p i t a l r e s o u r c e a v a i l a b i l i t y determines u t i l i z a t i o n as an e n a b l i n g v a r i a b l e i n the d e c i s i o n s t o h o s p i t a l i z e , then day ca re s u r g e r y as an a l t e r n a t i v e t o i n p a t i e n t c a re c o u l d se rve o n l y o r p r i m a r i l y t o expand the o v e r a l l volume of d i a g n o s t i c and t h e r a p e u t i c i n t e r v e n t i o n s , f o r a g i v e n s tock of i n p a t i e n t c a p a c i t y . Day ca re s u r g e r y would r e p r e s e n t an i n c r e a s e i n t o t a l h o s p i t a l c a p a c i t y c r e a t i n g more demand f o r h o s p i t a l s e r v i c e s , e i t h e r d i r e c t l y , through the beds t h a t i t f r e e s up i f some s u b s t i t u t i o n occur s a t the i n d i v i d u a l p a t i e n t l e v e l , o r b o t h . Un le s s i n p a t i e n t f a c i l i t i e s a re reduced t o same e x t e n t as day c a r e s u r g e r y i s i n c r e a s e d , any s u b s t i t u t i o n e f f e c t w i l l be a t most p a r t i a l , and day ca re su r ge ry w i l l be accompanied by g e n e r a t i o n of new h o s p i t a l u t i l i z a t i o n . S imul taneous dec rea se i n i n p a t i e n t bed supp l y w i t h i n c r e a s e i n day c a r e s u r g e r y c a p a c i t y c o u l d l e a d to more s u b s t i t u t i o n and l e s s g e n e r a t i o n from day c a r e su r ge ry o n l y i n c o n d i t i o n t h a t g e n e r a t i o n works through v a c a t e d beds. S u b s t i t u t i o n leads 13 t o lower occupancy f o r any g i ven bed s t o c k . I f r e s u l t a n t unused bed c a p a c i t y i s cu t o f f w i thout a l l o w i n g i t t o c r e a t e new demand f o r h o s p i t a l s e r v i c e s , then net r e d u c t i o n i n i n p a t i e n t u t i l i z a t i o n shou ld emerge. In an environment where i n p a t i e n t bed c a p a c i t y i s g e n e r a l l y d e c r e a s i n g , day c a r e s u r g e r y i s not n e c e s s a r i l y r e p r e s e n t i n g more s u b s t i t u t i o n and l e s s g e n e r a t i o n . Roemer's Law i m p l i e s t h a t i n p a t i e n t u t i l i z a t i o n f a l l s when supp ly o f beds i s r educed . I f day ca re s u r g e r y i s p l a y i n g a s u b s t i t u t i o n r o l e , then one would expect i n p a t i e n t u t i l i z a t i o n t o f a l l f a s t e r than i n absence of day ca re s u r g e r y . I f r e d u c t i o n of beds i s d i r e c t e d o n l y t o a l r e a d y unused c a p a c i t y ( i . e . , occupancy has been l e s s than 100 p e r c e n t ) , g e n e r a t i o n of new h o s p i t a l use may s t i l l r e s u l t from day c a r e s u r g e r y through s u b s t i t u t i o n and subsequent f i l l i n of v a c a t e d beds. In g e n e r a l , Roemer's Law has been assumed t o work e q u a l l y w e l l i n s i t u a t i o n s where bed c a p a c i t y i s i n c r e a s i n g and where i t i s d e c r e a s i n g . In o t h e r words, i n p a t i e n t u t i l i z a t i o n i s expec ted t o d e c l i n e the same amount when beds a r e reduced as i t i n c r e a s e s when beds a re added. A c c o r d i n g t o the supp l y model bed a v a i l a b i l i t y a f f e c t s h o s p i t a l u t i l i z a t i o n through the way i n which p h y s i c i a n s p r a c t i c e by i n t e r v e n i n g d e c i s i o n s t o h o s p i t a l i z e . One can h y p o t h e s i z e t h a t p h y s i c i a n s w i l l have more d i f f i c u l t i e s i n r e v i s i n g t h e i r h o s p i t a l i z a t i o n p a t t e r n s downwards when beds a re r educed , a f t e r a d a p t i n g t o a c e r t a i n h i g h e r l e v e l of h o s p i t a l u se , than upwards when bed c a p a c i t y 14 i s i n c r e a s e d . In t h e o r y , p h y s i c i a n s c o u l d t r y t o r e s i s t d e c r e a s e i n h o s p i t a l u t i l i z a t i o n when bed s tock i s r e d u c e d , up to the l e v e l where occupancy r a t e reaches i t s c e i l i n g . In p r a c t i c e , d e c l i n e i n supp l y of beds has o c c u r r e d so seldom t h a t t h e r e a re v e r y few r e s e a r c h r e s u l t s ion Roemer 's Law i n t h i s s i t u a t i o n . The emphasis i n t h i s s tudy i s t o t e s t the two compet ing models - the "med i ca l needs" model and the " s u p p l y " model - i n a p a e d i a t r i c p o p u l a t i o n ( 0 . - 14 y e a r s ) . Put i n o t h e r words, t h i s s tudy w i l l t e s t the a p p l i c a b i l i t y of Roemer's Law i n a c h i l d p o p u l a t i o n . The s tudy h y p o t h e s i s i s t h a t day c a r e s u r g e r y has an independent c a u s a l e f f e c t on p a e d i a t r i c i n p a t i e n t u t i l i z a t i o n i r r e s p e c t of the h o s p i t a l bed a v a i l a b i l i t y . I f an independent , one t o one s u b s t i t u t i o n e f f e c t i s f ound, the "med i ca l needs" model would be suppor ted and t h e r e would be a ' s a t i s f i e d need ' env i ronment . I f the s u b s t i t u t i o n e f f e c t i s l e s s , i t would mean t h a t day ca re s u r g e r y i s a l s o a s s o c i a t e d w i t h g e n e r a t i o n o f net new h o s p i t a l u t i l i z a t i o n . The n u l l hypo the s i s i s t h a t p a e d i a t r i c day c a r e s u r g e r y has no independent e f f e c t on i n p a t i e n t u t i l i z a t i o n . T h i s i m p l i e s t h a t day ca re su r ge ry a c t s mere l y as add-on to the o v e r a l l h o s p i t a l u t i l i z a t i o n ( s t r a i g h t add -on , no s u b s t i t u t i o n ) . The s tudy h y p o t h e s i s i n r e s p e c t t o bed supp l y i s t h a t p a e d i a t r i c h o s p i t a l bed c a p a c i t y has an independent c a u s a l e f f e c t on p a e d i a t r i c i n p a t i e n t u t i l i z a t i o n a l l o t h e r t h i n g s b e i n g e q u a l . 15 1 . 6 . T h e s i s Format Chapter two i n t h i s t h e s i s c o n t a i n s the arguments f o r i n t r o d u c i n g a day ca re su r ge ry program as an a l t e r n a t i v e f o r i n p a t i e n t c a r e . A t t e n t i o n i s a l s o p a i d to the response o f i n p a t i e n t u t i l i z a t i o n to day ca re su r ge ry and to the r o l e of bed s u p p l y i n d e t e r m i n i n g h o s p i t a l u t i l i z a t i o n . P o t e n t i a l o t h e r de te rminant s o f p a e d i a t r i c i n p a t i e n t u t i l i z a t i o n a r e a l s o d i s c u s s e d . T h i s d i s c u s s i o n i s based on a rev iew o f p r e v i o u s l y p u b l i s h e d s t u d i e s and aims to r e v e a l p o t e n t i a l confounders i n s t u d y i n g the r e l a t i o n s h i p between day ca re s u r g e r y use and i n p a t i e n t u t i l i z a t i o n i n a p a e d i a t r i c p o p u l a t i o n . Chapter t h r e e d e s c r i b e s the r e s e a r c h d e s i g n and da ta sources used i n t h i s s tudy . Necessary da ta m a n i p u l a t i o n and c o n s t r u c t i o n of independent and dependent v a r i a b l e s a r e a l s o d e s c r i b e d . Main s t a t i s t i c a l method, l i n e a r r e g r e s s i o n a n a l y s i s , i s p r e s e n t e d b r i e f l y . Chapter f o u r d e s c r i b e s the r e s u l t s of t h i s s tudy . Sequence of t h i s p r e s e n t a t i o n f o l l o w s t h a t of the s t a t i s t i c a l a n a l y s i s of the d a t a . Impacts of d i f f e r e n t p o t e n t i a l confounders on the r e l a t i o n s h i p between p a e d i a t r i c day ca re s u r g e r y use and i n p a t i e n t u t i l i z a t i o n a r e examined g r a d u a l l y . The main emphasis i s i n r e v e a l i n g p o t e n t i a l c a u s a l a s s o c i a t i o n s and 16 t e s t i n g the two competing models - the "med i ca l needs" model and the " s u p p l y m o d e l " . Chapter f i v e d i s c u s s e s the r e s u l t s o f t h i s s tudy w i t h r e f e r e n c e t o s tudy o b j e c t i v e s and q u e s t i o n s . A t t e n t i o n i s a l s o p a i d t o p o l i c y i m p l i c a t i o n s . Chapter c l o s e s w i t h c o n c l u s i o n s of the s tudy . 17 2. LITERATURE REVIEW 2 .1 . Why no t i n p a t i e n t care? Roth (1972) has d i v i d e d the c r i t i c i s m of h o s p i t a l i n p a t i e n t c a r e i n t o t h r e e c a t e g o r i e s . One c a t e g o r y o f c r i t i c i s m i s based m a i n l y on the s t u d i e s and c r i t i c a l commentary o f m e d i c a l and p u b l i c h e a l t h s p e c i a l i s t s and m e d i c a l c a r e i n v e s t i g a t o r s . Another c a t e g o r y i s based l a r g e l y on the work of s o c i o l o g i s t s and p s y c h o l o g i s t s . A t h i r d i s based ma in l y on the a n a l y s e s of economi s t s . S t u d i e s i n the f i r s t c a t e g o r y r e v e a l p h y s i c a l and m e d i c a l hazards of be ing h o s p i t a l i z e d . Any admi s s i on has p o t e n t i a l r i s k s as w e l l as b e n e f i t s . These r i s k s i n c l u d e i n c r e a s e d p r o b a b i l i t y of i a t r o g e n i c c o m p l i c a t i o n s , h o s p i t a l -a c q u i r e d i n f e c t i o n s , and mishaps caused by human and t e c h n i c a l e r r o r s (Schimmel 1964; Gros s , 1966; Roth , 1972). A l though i n f o r m a t i o n on the i n c i d e n c e o f h o s p i t a l - a c q u i r e d i n f e c t i o n s i s s u r p r i s i n g l y s c a r c e , i t i s assumed t h a t i n deve loped c o u n t r i e s 5 p e r c e n t of a l l admi t ted p a t i e n t s w i l l a c q u i r e an i n f e c t i o n d u r i n g h o s p i t a l i z a t i o n (Van F u r t h , 1982). The r a t e v a r i e s among the wards, the h i g h e s t u s u a l l y b e i n g r e p o r t e d f o r s u r g i c a l wards, f o l l o w e d by the m e d i c a l and o b s t e t r i c a l -g y n e c o l o g i c a l wards. Large surveys o f i n f e c t i o n s i n h o s p i t a l s i n Eng land and Wales showed t h a t 22.1 p e r c e n t of p a t i e n t s i n p a e d i a t r i c beds had community- and 4.1 p e r c e n t h o s p i t a l -18 a c q u i r e d i n f e c t i o n (Meers e t a 1. f 1981). A p r o s p e c t i v e s tudy of h o s p i t a l - a c q u i r e d i n f e c t i o n s i n a l a r g e p a e d i a t r i c h o s p i t a l i n New York S t a t e showed e x a c t l y the same 4.1 p e r c e n t a t t a c k r a t e o f nosocomia l i n f e c t i o n s ( W e l l i v e r and M c L a u g h l i n , 1984). H o s p i t a l i n f e c t i o n s tend to be more r e s i s t a n t t o t rea tment than those a c q u i r e d i n the community. A p r o s p e c t i v e s tudy of the type and f r equency o f h o s p i t a l c o m p l i c a t i o n s showed t h a t d e l e t e r i o u s ep i sodes b e f e l l 20 p e r c e n t of a l l p a t i e n t s admi t ted t o h o s p i t a l . Major c o m p l i c a t i o n s o c c u r r e d i n f i v e p e r c e n t of admis s ions (Schimmel, 1964). The p r o b a b i l i t y of untoward ep i s ode was r e l a t e d to the l e n g t h of s t a y and thus r e f l e c t s the g e n e r a l haza rd of h o s p i t a l i z a t i o n . In a d d i t i o n , a g r e a t p o r t i o n of n u r s i n g , m e d i c a t i o n and t e c h n i c a l e r r o r s go u n n o t i c e d , because they do no s e r i o u s harm t o the p a t i e n t . Duff e t a1 . (197 2) showed i n a u t i l i z a t i o n rev iew o f t h r e e community h o s p i t a l s and one major t e a c h i n g h o s p i t a l t h a t o n e - t h i r d of p a e d i a t r i c p a t i e n t s r e c e i v e d l e s s than o p t i m a l c a r e . M i suse of a n t i b i o t i c s and q u e s t i o n a b l e use o f o t h e r drugs accounted f o r 7 9 p e r c e n t of i n s t a n c e s o f q u e s t i o n a b l e c a r e . I a t r o g e n i c a c c i d e n t s and d i s e a s e s have appeared i n the s c i e n t i f i c med i ca l l i t e r a t u r e i n f r e q u e n t l y i n the 1970s and the 1980s. P u b l i s h e d papers have m a i n l y d e a l t w i t h m e d i c a t i o n e r r o r s (Hynniman e_£ a l . f 1970; Solomon e t a l . , 1984) and mys te r i ou s deaths i n p a e d i a t r i c wards ( I s t r e e t a 1 . r 1985; Bueh le r e t a l . , 1985). However, the g e n e r a l news media and, p a r t i c u l a r l y the l e g a l 19 arena seem t o have p i c k e d up t h i s s u b j e c t w i t h i n c r e a s i n g i n t e r e s t . The second c a t e g o r y of s t u d i e s r e v e a l s p s y c h o s o c i a l hazards of h o s p i t a l i z a t i o n . In the h o s p i t a l , one's l i f e i s t o t a l l y d i s r u p t e d , not so much by one's i l l n e s s o r treatment, but by the o r g a n i z a t i o n of r o u t i n e s designed f o r the convenience of ot h e r people who are not i n t e r e s t e d i n one's o v e r a l l w e l f a r e , but o n l y i n v e r y l i m i t e d aspects of i t (Roth, 1972). The l a c k of c o n t r o l over one's treatment (and many a c t i v i t i e s of d a i l y l i v i n g ) t o g e t h e r w i t h a l i e n environment can be, a t b e s t , j u s t a nuisance t o an a d u l t . But f o r a c h i l d a h o s p i t a l experience can p r e c i p i t a t e s h o r t - and long-term emotional problems (Schimmel, 1964). The mental w e l l b e i n g of h o s p i t a l i z e d c h i l d r e n became a major concern when the s i g n i f i c a n c e of the m o t h e r - c h i l d r e l a t i o n s h i p t o the development of the c h i l d was r e c o g n i z e d d u r i n g the 1940s ( S p i t z , 1945; Freud, 1951). In the 1950s a s e r i e s of s t u d i e s d e s c r i b e d the syndrome: p r o t e s t , d e s p a i r , detachment i n h o s p i t a l i z e d c h i l d r e n (Robertson, 1953, 1970). Although p a e d i a t r i c wards were d i f f e r e n t then, and the emphasis was c e n t r e d almost e n t i r e l y on p h y s i c a l c a r e w i t h l i t t l e o r no concern f o r the s o c i a l and emotional needs of c h i l d r e n and t h e i r p a r e n t s , the p s y c h o l o g i c a l l y u p s e t t i n g e f f e c t of h o s p i t a l i z a t i o n has not t o t a l l y d i sappeared a f t e r the r e c o g n i t i o n of these hazards. Vernon e t a l . (1965) p r o v i d e a thorough review of the l i t e r a t u r e on the p s y c h o l o g i c a l e f f e c t s of h o s p i t a l i z a t i o n . S e v e r a l s t u d i e s 2 0 showed t h a t the emot iona l d i s t u r b a n c e s were not l i m i t e d t o the p e r i o d of h o s p i t a l s t a y but c o n t i n u e d a f t e r d i s c h a r g e f o r s e v e r a l days o r even y e a r s . U n f a m i l i a r i t y o f the h o s p i t a l s e t t i n g , s e p a r a t i o n from pa ren t s and age of the c h i l d were the most suppor ted determinant s of p s y c h o l o g i c a l upse t i n the l i t e r a t u r e . F i n d i n g s t h a t p o i n t e d t o the u n f a m i l i a r i t y of the h o s p i t a l s e t t i n g as a source of emot iona l problems came from two d i f f e r e n t types of s t u d i e s . C o n t r o l l e d t r i a l s on p s y c h o l o g i c a l p r e p a r a t i o n p r i o r t o h o s p i t a l i z a t i o n showed dec rea sed p o s t h o s p i t a l p s y c h o l o g i c a l d i s t u r b a n c e s . However, p r e p a r a t i o n f o r the h o s p i t a l e x p e r i e n c e d i d not reduce the a n x i e t y d u r i n g the h o s p i t a l c a re (Vernon e t a 1. f 1965). The o t h e r da ta sugges t i ng t h a t u n f a m i l i a r i t y p l a y s a major r o l e i n p s y c h o l o g i c a l upset came from s t u d i e s on c h i l d r e n ' s b e h a v i o r d u r i n g h o s p i t a l i z a t i o n . These da ta showed t h a t c h i l d r e n appear l e s s upse t o r h a p p i e r as h o s p i t a l i z a t i o n p r o g r e s s . A l though these f i n d i n g s can be i n t e r p r e t e d v a r i o u s ways, they seem much l i k e changes i n w e l l c h i l d r e n ' s r e a c t i o n s to an u n f a m i l i a r p layroom (Vernon e t a 1 . f 1965). On the o t h e r hand, t h e r e i s growing ev idence r e l a t e d t o su r ge ry t o suggest t h a t one o p e r a t i o n does not p repare one f o r a l l o t h e r s . In f a c t c h i l d r e n who have had su r ge ry b e f o r e tend t o be more anx ious about subsequent o p e r a t i o n s than those who a re e x p e r i e n c i n g s u r g e r y f o r the f i r s t t ime ( A z a r n o f f , 1975; C r o c k e r , 1978). In s p i t e o f the r e c e n t improvement i n many p a e d i a t r i c wards, the d i s t r e s s which young c h i l d r e n e x p e r i e n c e when they a re 21 admi t ted t o h o s p i t a l and the reby sepa ra ted from t h e i r p a r e n t s , s i b l i n g s , and home environment i s s t i l l t h e r e . Data r e l e v a n t t o the e f f e c t s o f s e p a r a t i o n i n d i c a t e t h a t t h i s f a c t o r c o n t r i b u t e s t o upset both d u r i n g and immed ia te l y f o l l o w i n g h o s p i t a l i z a t i o n . There i s a p o s i t i v e r e l a t i o n s h i p between degree of s e p a r a t i o n and p s y c h o l o g i c a l upset (Vernon e t a 1., 1965). B r a i n and Mac lay (1968) have shown i n a c o n t r o l l e d s tudy t h a t the i n c i d e n c e of emot i ona l c o m p l i c a t i o n s i s s i g n i f i c a n t l y lower i n c h i l d r e n who a r e h o s p i t a l i z e d w i th t h e i r mother than i t i s w i t h unaccompanied c h i l d r e n . The i n v e s t i g a t i o n s i n v o l v i n g age suggested t h a t t h e r e i s a c u r v i l i n e a r r e l a t i o n s h i p between t h i s v a r i a b l e and p s y c h o l o g i c a l u p s e t . C h i l d r e n between app rox ima te l y s i x months and t h r e e t o f o u r year s of age appeared to be p a r t i c u l a r l y v u l n e r a b l e t o upset d u r i n g h o s p i t a l i z a t i o n ; younger i n f a n t s and o l d e r c h i l d r e n appeared t o be l e s s v u l n e r a b l e . T h i s r e l a t i o n s h i p was l e s s c l e a r , when c h i l d r e n ' s r e a c t i o n s f o l l o w i n g h o s p i t a l i z a t i o n were c o n s i d e r e d (Vernon e_£ a l 1 9 6 5 ) . O l d e r c h i l d r e n may be p a r t i c u l a r l y concerned w i th l o s s of independence and c o n t r o l as w e l l as body d i s f i g u r e m e n t d u r i n g h o s p i t a l i z a t i o n ( P e t r i l l o and Sanger, 1972). The t h i r d c a t e g o r y of c r i t i c i s m argues t h a t h o s p i t a l t rea tment i s an ex t reme ly c o s t l y way t o t r e a t most a i l m e n t s 22 (Roth, 1972). Evans pt. a l . (1978) have , f o r example, c a l c u l a t e d t h a t a p a e d i a t r i c s u r ge ry ep i sode c o s t s 50 - 70 p e r c e n t l e s s i n day ca re su r ge ry u n i t than on the i n p a t i e n t wards. A l though h o s p i t a l t reatment c o s t s a r e not a t h r e a t t o the i n d i v i d u a l p a t i e n t , they a re i n aggregate an economic burden to Canadian tax paye r s . Dur ing the q u a r t e r c e n t u r y from 1946 to 1971 h e a l t h ca re expend i tu re s r o se r a p i d l y , both i n d o l l a r terms and as a percentage o f t o t a l n a t i o n a l e x p e n d i t u r e . Expend i tu re s on h o s p i t a l c a r e made up the l a r g e s t share o f the t o t a l , and a l s o showed the most r a p i d growth: from 1.27 p e r c e n t of g ross n a t i o n a l p roduc t i n 1946 to 3.33 p e r c e n t i n 1971 (Evans, 1984). In the mid 1980s, h o s p i t a l c o s t s make about h a l f of the p u b l i c h e a l t h c a r e e x p e n d i t u r e s i n B.C. ( P rov ince o f B r i t i s h Co lumbia , 1985). Even a s m a l l s h i f t i n u t i l i z a t i o n from h o s p i t a l c a r e t o l e s s expens i ve a l t e r n a t i v e s c o u l d mean c o n s i d e r a b l e sav ings a t the p r o v i n c i a l o r n a t i o n a l l e v e l . I t i s no wonder t h a t development of l e s s expens ive o u t p a t i e n t s e r v i c e s has been recommended as a major means of l ower ing and c o n t r o l l i n g h o s p i t a l e x p e n d i t u r e s (Canada, 1964 ). In the b e g i n n i n g of the 1970s an attempt was made to r e s t r u c t u r e the whole Canadian h e a l t h c a re system and to s h i f t the p o l i c y emphasis from h o s p i t a l c a re t o proposed community h e a l t h c e n t r e s (Conference of H e a l t h M i n i s t e r s , 1972). One of the major reasons beh ind the community h e a l t h c e n t r e p r o j e c t , s e t up by the M i n i s t e r o f N a t i o n a l H e a l t h and We l f a re i n 1971, was a 23 b e l i e f t h a t some s h i f t from the p r e s e n t emphasis on acu te h o s p i t a l i n p a t i e n t c a r e t o o t h e r forms of h e a l t h c a r e o f f e r a means of s l ow ing the r a t e of i n c r e a s e i n h e a l t h s e r v i c e s spend ing . (Conference o f Hea l th M i n i s t e r s , 1972). H o s p i t a l i n p a t i e n t c a re has always some d i sadvantages i n a d d i t i o n t o b e n e f i t s t h a t i t p roduces . Every ep i sode of ca re i s a s s o c i a t e d w i t h r i s k of h o s p i t a l - a c q u i r e d i n f e c t i o n and i a t r o g e n i c c o m p l i c a t i o n s . The r i s k i n c r e a s e s w i t h i n c r e a s i n g l e n g t h o f s t a y . I n p a t i e n t c a re i s a l s o expens i ve r e l a t i v e t o ambula tory c a r e . U n d e s i r a b l e p s y c h o s o c i a l e f f e c t s of h o s p i t a l i z a t i o n on c h i l d r e n a re a s p e c i a l concern i n p a e d i a t r i c s . These reasons emphasize the need f o r s h i f t i n g p a t i e n t c a re from a c t i v e h o s p i t a l admi s s ion to a l t e r n a t e i n p a t i e n t o r ambulant f a c i l i t i e s whenever i t i s m e d i c a l l y p o s s i b l e . H o s p i t a l c e n t r e d h e a l t h c a re system i s l o s i n g i t s glamour i n many deve loped c o u n t r i e s because of i t s h i g h c o s t s r e l a t i v e to o t h e r arrangements . The i n t e r n a t i o n a l community has a l s o emphasized a l t e r n a t i v e approaches i n s o l v i n g the h e a l t h problems o f the p o p u l a t i o n (WHO, 1978, 1979). In Canada, the La londe Report ( La londe, 1974) was a move i n t h i s d i r e c t i o n , but i n s p i t e of wide use i n p o l i t i c a l speeches , i t has had v e r y l i t t l e impact on Canadian h e a l t h c a re p o l i c i e s . D e s p i t e o f the r a t i o n a l e f o r d e c r e a s i n g i n p a t i e n t u t i l i z a t i o n i n the p o p u l a t i o n as a whole and i n the c h i l d p o p u l a t i o n , i n 24 p a r t i c u l a r , t h e r e a re f a c t o r s which work j u s t t o the o p p o s i t e d i r e c t i o n . The Canadian h e a l t h c a r e system i s p r o b a b l y more h o s p i t a l - c a r e - o r i e n t e d than t h a t i n many o t h e r Western c o u n t r i e s f o r h i s t o r i c a l r ea sons . F i r s t l y , w i t h the h e l p of the H o s p i t a l C o n s t r u c t i o n Grants i n the l a t e 1940s and and i n the 1950s, Canadian p r o v i n c e s b u i l t up a c o n s i d e r a b l e h o s p i t a l bed c a p a c i t y . Second ly , u n i v e r s a l h o s p i t a l i n s u r a n c e i n Canada was i n t r o d u c e d b e f o r e the m e d i c a l i n s u r a n c e ( T a y l o r , 1978). T h i s d e c i s i o n enhanced the r o l e of h o s p i t a l s i n the Canadian h e a l t h c a r e system. H o s p i t a l s have a l s o o t h e r , more covered f u n c t i o n s than j u s t the p r o v i s i o n of h e a l t h s e r v i c e s . As C r i c h t o n (1972) d e s c r i b e s i t : " H o s p i t a l s a re symbols of community c a r e . They p r o v i d e a s e c u r i t y b l a n k e t f o r i s o l a t e d and, w i t h the improvement of t r a n s p o r t a t i o n systems, l e s s i s o l a t e d communit ies i n Canada. They p r o v i d e po ten t m a t e r i a l f o r p o l i t i c a l c o n t r o v e r s y and the p o l i t i c i a n s f i n d i t hard to r e s i s t o r g a n i z e d , emot iona l community groups who a re de termined t o keep l o c a l h o s p i t a l s open. T h i s i s an i n t e r n a t i o n a l phenomenon. I t appears t o be p o l i t i c a l l y i m p o s s i b l e t o c l o s e h o s p i t a l s once they have been opened because they a re c e n t r e s o f employment and focuses of bus ines s f o r s m a l l towns" ( C r i c h t o n , 1972, p. 5 -1 ) . 2 5 2.2. Day c a r e s u r g e r y - a l t e r n a t i v e f o r i n p a t i e n t c a r e 2 . 2 . 1 . D e f i n i t i o n There i s no g e n e r a l l y accep ted d e f i n i t i o n f o r day c a r e s u r g e r y . U s u a l l y t h i s term r e f e r s t o h o s p i t a l s e r v i c e which a l l ows admi s s i on and d i s c h a r g e on the day of s u r g e r y . I t r e q u i r e s g e n e r a l a n a e s t h e s i a and i s r e s e r v e d f o r e l e c t i v e o p e r a t i v e p rocedures (Robinson and C l a r k e , 1980). The p a t i e n t r e c e i v e s the same h o s p i t a l t reatment w i t h r e g a r d to c a r e , s a f e t y , and m e d i c a l r e c o r d s as would an i n p a t i e n t . Robinson and C l a r k e (1980) d i s t i n g u i s h day ca re su r ge ry from o u t p a t i e n t s u r g e r y , which c o u l d be done as w e l l i n d o c t o r s ' o f f i c e s . In the m e d i c a l l i t e r a t u r e , day ca re su r ge ry i s o f t e n c a l l e d o u t p a t i e n t su r ge ry (Stephens and Dudley, 1961), ambulatory o r day case s u r g e r y ( A t w e l l e t a ] . , 1973) and s h o r t - s t a y su r ge ry . In Canada, day c a r e su r ge ry i s housed i n h o s p i t a l s w i t h few e x c e p t i o n s ( e . g . , a b o r t i o n c l i n i c s ) . In U n i t e d S t a t e s , f r e e s t a n d i n g f a c i l i t i e s , o f t e n c a l l e d s u r g i c e n t e r s , which a re not p a r t of a h o s p i t a l , have become another model f o r d e l i v e r i n g day ca re s u r g i c a l s e r v i c e s (C loud , 1972). When day c a r e su r ge ry became an i n s u r e d h o s p i t a l b e n e f i t i n B.C. i n 1968, i t needed a l s o a j u d i c i a l d e f i n i t i o n . A c c o r d i n g t o the H o s p i t a l Insurance A c t Regu l a t i on s ( P rov ince of B r i t i s h Co lumb ia , 1968) the M i n i s t e r of H e a l t h s h a l l d e f i n e day ca re s u r g i c a l s e r v i c e s and s h a l l s p e c i f y the b e n e f i t s which a re to 2 6 be made a v a i l a b l e . A t the t ime the d e c i s i o n was made f o r p r o v i s i o n o f t h i s b e n e f i t , t h e r e was c o n s i d e r a b l e d i s c u s s i o n as t o the t ype of case t h a t would be s u i t a b l e f o r coverage , and d i s c u s s i o n a l s o of the method o f d e f i n i n g a c c e p t a b l e cases and p rocedure (P rov ince of B r i t i s h Co lumbia , 1983). Se r i ou s c o n s i d e r a t i o n was o r i g i n a l l y g i v e n t o the development of a l i s t of p rocedures and d iagnoses which would be e l i g i b l e . However, i t was f e l t t h a t such a l i s t would be s u b j e c t t o con s t an t amendment, r e v i s i o n and a d d i t i o n s , and h o s p i t a l c l e r i c a l p e r s o n n e l would have c o n t i n u i n g d i f f i c u l t i e s i n t e r p r e t i n g a d m i t t i n g d iagnoses and types of p rocedures a g a i n s t the background o f a c o n s t a n t l y chang ing e l i g i b l e l i s t . I t was t h e r e f o r e d e c i d e d t h a t a broad g e n e r a l d e f i n i t i o n of what was i n t e n d e d f o r coverage was a s u p e r i o r method of d e a l i n g w i t h the problem (P rov ince of B r i t i s h Co lumbia , 1983). The d e f i n i t i o n of day c a r e su r ge ry e l i g i b l e f o r i n s u r a n c e b e n e f i t s i n B.C. i s based an i d e a t h a t day c a r e s u r g i c a l s e r v i c e s a r e a compact form of i n p a t i e n t c a r e , and as such , de se rve the same q u a l i t y c o n t r o l c o n s i d e r a t i o n s p r o v i d e d to i n p a t i e n t s . The a t t e n d i n g p h y s i c i a n s i n the h o s p i t a l s a re t h e r e f o r e expected to p r o v i d e a complete m e d i c a l r e c o r d f o r a day ca re adm i s s i on , and these r e c o r d s a re s u b j e c t t o the u s u a l r ev i ew taken by the h o s p i t a l ' s M e d i c a l Records Committee to e s t a b l i s h q u a l i t y c o n t r o l , and a l s o t o a s s i s t i n a s s e s s i n g p r o p e r u t i l i z a t i o n of the program (P rov ince of B r i t i s h Co lumb ia , 1983). The p r imary group of cases a re those 27 e l e c t i v e and n o n e l e c t i v e d i a g n o s t i c and/or t rea tment p rocedure s r e q u i r i n g the use o f h o s p i t a l f a c i l i t i e s and a g e n e r a l a n a e s t h e t i c . An a d d i t i o n a l group which a r e a c c e p t a b l e a re those p rocedures which would n o r m a l l y be c a r r i e d out under g e n e r a l a n a e s t h e s i a , but where the a t t e n d i n g p h y s i c i a n has e l e c t e d to use l o c a l a n a e s t h e s i a . A t h i r d group o f a c c e p t a b l e cases a re endoscop i c procedures c a r r i e d out under e i t h e r l o c a l o r g e n e r a l a n a e s t h e s i a . I t i s f e l t t h a t h o s p i t a l f a c i l i t i e s a r e r e q u i r e d f o r c y s t o s c o p y , bronchoscopy, esophagoscopy, g a s t r o s c o p y , e t c , , and o c c a s i o n a l l y s i gmoidoscopy. Regard ing s i gmo idoscopy, t h i s p rocedure does not n o r m a l l y r e q u i r e complete h o s p i t a l f a c i l i t i e s , and i s u s u a l l y per formed as a s imp le o f f i c e o r h o s p i t a l o u t p a t i e n t s e r v i c e . O c c a s i o n a l l y , however, f u l l s e r v i c e s of the h o s p i t a l may be r e q u i r e d , and i n such cases t h i s endoscop ic p rocedure would then be a c c e p t a b l e . A f o u r t h group of a c c e p t a b l e p rocedures a re those r e l a t e d t o c e r t a i n co smet i c and p l a s t i c s u r g i c a l p rocedures which may be c a r r i e d out under a l o c a l a n a e s t h e t i c . S imple p rocedures such as e x c i s i o n of c y s t s , removal o f war t s , t o e n a i l s , e t c . , a re c o n s i d e r e d as "minor su r ge ry " , and c a r r i e d out as a s imp le o f f i c e o r h o s p i t a l o u t p a t i e n t s e r v i c e . However, i t i s r e c o g n i z e d t h a t c e r t a i n p l a s t i c s u r g i c a l , o p h t h a l m o l o g i c a l , and o t h e r p rocedures on the f a c e do r e q u i r e a degree of ca re and a t t e n t i o n which may c a l l f o r f u l l o p e r a t i n g room and o t h e r h o s p i t a l f a c i l i t i e s ( P rov ince of B r i t i s h Co lumbia , 1983). 28 2 .2 .2 . A b r i e f h i s t o r y o f p a e d i a t r i c day c a r e s u r g e r y Day c a r e s u r g e r y has been p r a c t i c e d f o r a lmost a c e n t u r y , but i t has been o n l y d u r i n g the l a s t two decades t h a t i t has ga ined more impor tance . James N i c h o l l i n 1909 r e p o r t e d a s e r i e s of 8,988 p a e d i a t r i c cases t r e a t e d as o u t p a t i e n t s a f t e r o p e r a t i o n s per formed from 1899 to 1908 a t the Glasgow Roya l H o s p i t a l f o r S i c k C h i l d r e n ( N i c h o l l , 1909). He conc luded t h a t a much l a r g e r share of the o p e r a t i v e work i n a c h i l d r e n ' s h o s p i t a l shou ld be done on an o u t p a t i e n t b a s i s and t h a t use of i n p a t i e n t f a c i l i t i e s f o r p a t i e n t s who can be hand led on a day b a s i s was a waste of h o s p i t a l r e s o u r c e s . P a t i e n t s t r e a t e d i n the o u t p a t i e n t department shou ld be l a r g e l y i n f a n t s and young c h i l d r e n . He added t h a t a f t e r o p e r a t i o n they a re e a s i l y c a r r i e d home i n t h e i r mother ' s arms and r e s t t h e r e more q u i e t l y on the whole than anywhere e l s e ( N i c h o l l , 1909). In 19 38, H e r z f e l d a t the Roya l Ed inburgh H o s p i t a l f o r S i c k c h i l d r e n r e p o r t e d a s e r i e s of 1,000 o p e r a t i o n s f o r i n d i r e c t i n g u i n a l h e r n i a i n c h i l d r e n ( H e r z f e l d , 1938). Many of these were o p e r a t e d upon under g e n e r a l a n e s t h e s i a i n an o u t p a t i e n t f a c i l i t y w i thou t h o s p i t a l admis s ion f o r reason of s a f e t y , economy, and conven ience . In 1949, the E v e l i n a C h i l d r e n ' s H o s p i t a l i n London s t a r t e d o p e r a t i n g on i n f a n t s and c h i l d r e n as day cases i n o r d e r t o reduce the i n c i d e n c e of p o s t -o p e r a t i v e i n f e c t i o n s (Lawr ie , 1964). In 1957, Othersen and C l a t w o r t h y (1968) began per fo rm ing h e r n i o r r a p h i e s on i n f a n t s under 18 months of age on a day b a s i s and r e p o r t e d no major 29 c o m p l i c a t i o n s o r deaths i n over 350 p a t i e n t s d u r i n g a t e n year p e r i o d . They a l s o r e p o r t e d a s i g n i f i c a n t r e d u c t i o n i n p o s t -o p e r a t i v e i n f e c t i o n s i n o u t p a t i e n t s . The C h i l d r e n ' s H o s p i t a l i n Vancouver has been a l e a d e r i n p r o v i d i n g s u r g i c a l day care f o r c h i l d r e n i n B r i t i s h Columbia. I t began d e v e l o p i n g t h i s c a p a c i t y i n the l a t e 1960s, and i n October 1969 i t e s t a b l i s h e d a nine-bed day care surgery u n i t (Davenport et a 1. f 1971). 2.2.3. S a f e t y of p a e d i a t r i c day c a r e s u r g e r y S e v e r a l s t u d i e s have shown the f e a s i b i l i t y of day care s u r g e r y as an a l t e r n a t i v e t o acute h o s p i t a l i z a t i o n (Farquharson, 1955; Stephens and Dudley, 1961; Lawrie, 1964; Othersen and Clatworthy, 1968; Innes e t a 1. f 1968; Chiang e t •al • r 1968; Davenport et a 1 . f 1971; Lee, 1971; Shah et a l . r 1972; A t w e l l et a 1 . . 1973; Rudd, 1973; Lord, 1974; Lewis, 1975). I t s s u i t a b i l i t y f o r c h i l d r e n has been demonstrated w i t h s e v e r a l s p e c i a l t i e s , i n c l u d i n g d e n t a l (Smith et a l . . 1978), ophthalmology (Hadaway et a1. f 1977), o r t h o p e d i c s (Smith and Young, 1976), and u r o l o g y (Kroovand and P e r l m u t t e r , 1978). Shah et a l . (1972) conducted a quasirandomized c o n t r o l l e d t r i a l on m e d i c a l c o m p l i c a t i o n s and p a r e n t a l a t t i t u d e s r e l a t e d t o p a e d i a t r i c day care surgery a t C h i l d r e n ' s H o s p i t a l i n Vancouver. F i v e s u r g i c a l procedures - h e r n i a r e p a i r , c y stoscopy, s q u i n t r e p a i r , myringotomy, and d e n t a l r e s t o r a t i o n 30 - were s e l e c t e d f o r s tudy because they compr i sed about 82 p e r c e n t of a l l s u r g i c a l p rocedures a t t h a t t ime which had been s e l e c t e d as s u i t a b l e f o r su r ge ry on a day b a s i s . C h i l d r e n i n the c o n t r o l group were admi t ted to the ward f o r 1 to 3 days a f t e r s u r g e r y , and those i n the day ca re s u r g e r y group were d i s c h a r g e d home the day of su r ge ry . The a n a e s t h e t i c and g e n e r a l c o m p l i c a t i o n s were few and m i l d i n degree and not s i g n i f i c a n t l y d i f f e r e n t i n the two groups , except f o r cough and g e n e r a l d i s p o s i t i o n . A s i g n i f i c a n t l y g r e a t e r p r o p o r t i o n of p a t i e n t s i n the day ca re su r ge ry group had a cough on the day of o p e r a t i o n and on the f i r s t p o s t o p e r a t i v e day compared t o those i n the c o n t r o l group, whereas a s i g n i f i c a n t l y l a r g e r number of p a t i e n t s i n the c o n t r o l group had a poor g e n e r a l d i s p o s i t i o n ( e . g . , unhapp ines s ) . A s i g n i f i c a n t l y l a r g e r number of p a t i e n t s i n the day ca re su r ge ry group r e p o r t e d p a i n a t the s i t e o f o p e r a t i o n a f t e r h e r n i a r e p a i r and p a i n f u l v o i d i n g a f t e r c y s t o s copy compared to the p a t i e n t s i n the c o n t r o l group. I t was suggested t h a t p a r t of t h i s d i f f e r e n c e was due t o b e t t e r o b s e r v a t i o n of c h i l d r e n by t h e i r pa ren t s a t home than by the n u r s i n g s t a f f a t the h o s p i t a l . The s t u d i e s o f p a r e n t a l c h o i c e i n d i c a t e d t h a t 78 p e r c e n t of pa ren t s i n v o l v e d i n the day ca re su r ge ry group p r e f e r r e d i t , and 75 p e r c e n t of the remainder would have been s a t i s f i e d i f o n l y one n i g h t had been spent i n h o s p i t a l (Shah e t a 1. f 1972). The au thor s conc luded t h a t day c a r e su r ge ry i s s a f e and a c c e p t a b l e , not o n l y t o p h y s i c i a n s , but a l s o t o p a r e n t s . They a l s o ment ioned t h a t the widespread p u b l i c i t y of. the day ca re 31 s u r g e r y u n i t had r e s u l t e d i n pa rent s a s k i n g t h e i r a t t e n d i n g p h y s i c i a n s f o r t h i s form of c a r e . The r a t e of subsequent admis s ion to h o s p i t a l a f t e r day ca re s u r g e r y seems to v a r y . Davenport e t a l . (1971) found t h a t a p p r o x i m a t e l y 5 p e r c e n t of the c h i l d r e n who were day ca re s u r g i c a l p a t i e n t s of B.C. C h i l d r e n ' s H o s p i t a l were sub sequen t l y admi t ted to h o s p i t a l . The most f r e q u e n t reasons f o r admi s s i on were r e s p i r a t o r y problems (hoarseness o r c roupy cough) , a d d i t i o n a l m e d i c a l prob lems, and v o m i t i n g . Others have r e p o r t e d lower admis s ion r a t e s : 9 out of more than 8,500 c h i l d r e n (Steward, 1973) and 1.7 p e r c e n t (Ah l g ren , 1973). In s p i t e o f s tudy r e s u l t s on the s u i t a b i l i t y and s a f e t y of day c a r e s u r g e r y , some c o n t r o v e r s y seems t o remain i n the m e d i c a l community i n r e s p e c t t o c e r t a i n s u r g i c a l p r o c e d u r e s . T o n s i l l e c t o m y and adenoidectomy, by f a r the most common s u r g i c a l p rocedure i n c h i l d r e n (Wennberg and Kimm, 1977), i s u s u a l l y c o n s i d e r e d u n s u i t a b l e f o r su r ge ry on a day b a s i s by the m e d i c a l community (Shah and Rob inson, 1977; Sheps, 1980; Evans e t a 1. f 1983). However, Ch iang e t a1 . (1968) r e p o r t e d on 4 0,000 t o n s i l l e c t o m i e s performed on a day c a r e b a s i s w i thou t any major c o m p l i c a t i o n s , over twenty yea r s agol 32 2.2 .4 . P a e d i a t r i c day c a r e s u r g e r y l o a d and p rocedure s P a e d i a t r i c day c a r e su r ge ry has been promoted f o r t h r e e r e a s o n s . F i r s t , i t m in imizes emot iona l d i s t u r b a n c e because i t reduces the s e p a r a t i o n of the young c h i l d and pa ren t t o a few hour s . Second, i t reduces the r i s k of h o s p i t a l - a c q u i r e d i n f e c t i o n . T h i r d , the c o s t i s s i g n i f i c a n t l y lower than when per formed on an i n p a t i e n t b a s i s , w i thou t compromis ing the q u a l i t y of c a r e (Robinson and C l a r k e , 1980). In the l a t e 1960s, Robinson e t a l . (1969) e s t ima ted t h a t t w o - t h i r d s of the c h i l d r e n seen i n a p a e d i a t r i c r e f e r r a l c e n t r e r e q u i r e d c o n v e n t i o n a l h o s p i t a l c a re and 23.2 p e r c e n t q u a l i f i e d f o r day c a r e s u r g e r y . The need f o r a l t e r n a t i v e s t o i n p a t i e n t su r ge ry was emphas ized. S i n c e the d e c i s i o n t o i n c l u d e day c a r e s u r g e r y i n the B.C. h o s p i t a l i n s u r a n c e b e n e f i t s , the i n c i d e n c e of p a e d i a t r i c day ca re su rgery has i n c r e a s e d a lmost f i v e f o l d from 4.6 per 1,000 p o p u l a t i o n (0-14 yea r s ) i n 1968 to 22.8/1,000 i n 1982/83. Day ca re su r ge ry has been r e p o r t e d to compr i se 20 p e r c e n t (Steward, 1973), 33 p e r c e n t (Ah l g ren , 1973), and 50 p e r c e n t ( A t w e l l , 1978) of the t o t a l p a e d i a t r i c s u r g i c a l l o a d and cover s a wide range of p r o c e d u r e s . In B.C. day c a r e s u r g e r y compr ised 46.2 p e r c e n t of t o t a l p a e d i a t r i c s u r g i c a l cases i n 1982/83. In 1976, the most common broad p rocedure c a t e g o r i e s i n p a e d i a t r i c day ca re su r ge ry i n B.C. were o t o r h i n o l a r y n g o l o g y , d e n t a l , o r t h o p e d i c s , u r o l o g y , p l a s t i c , d i a g n o s t i c endoscopy, 33 and ophtha lmology (Robinson and C l a r k e , 1980). A c c o r d i n g t o the 1982/83 da ta i n a d m i s s i o n - s e p a r a t i o n database f o r day ca re s u r g e r y i n B.C. (kept by M i n i s t r y of H e a l t h , H o s p i t a l Programs) the se seven c a t e g o r i e s were s t i l l the most common (Tab le 2 ) . Myringotomy was, by f a r , the most common o p e r a t i v e p rocedure both i n 1976 and i n 1982/83 f o l l o w e d by c y s t o s c o p y and r e s t o r a t i o n of t o o t h (Tab le 3). 2.3. E s t ima te s o f p o t e n t i a l c o s t s av ing s r e l a t e d t o day c a r e s u r g e r y A l though the i n t r o d u c t i o n of day ca re su r ge ry l i e s h e a v i l y on i t s t h e r a p e u t i c s u p e r i o r i t y i n m i n i m i z i n g u n d e s i r a b l e e f f e c t s o f h o s p i t a l i z a t i o n , i t has been a l s o r e c o g n i z e d t h a t t h i s form of c a re shou ld l e a d t o s i g n i f i c a n t economic s av ing s . Evans (1980) has c r i t i c a l l y rev iewed the l i t e r a t u r e on c o s t s a v i n g a spec t s of day ca re su r ge ry both i n p a e d i a t r i c and i n a d u l t p r a c t i c e . Most of the s t u d i e s were done i n the U n i t e d S t a t e s . H i s r ev iew can be summarized as f o l l o w s : 1) The e a r l i e r s t u d i e s on day ca re s u r g e r y ( l a t e 1960s and e a r l y 1970s) g e n e r a l l y were d e s c r i p t i o n s of the u n i t s themselves and c o n t a i n e d l i s t s of types of p rocedures per formed, c r i t e r i a f o r p a t i e n t s e l e c t i o n , and more o r l e s s d e t a i l e d d e s c r i p t i o n s of t e c h n i q u e . Re ferences t o c o s t s c o n s i s t e d of o f f -hand s tatements t h a t o b v i o u s l y c o s t s must be lower. 34 Table 2 Most Common Operative Categories i n Day Care Surgery i n the Paediatric (0-14 years) Age Group i n B.C. i n 1976 and i n 1982/83 1976 1 1982/83 2 OPERATIVE CATEGORY % % O t o r h i n o l a r y n g o l o g y 32 .8 34.3 D e n t a l s u r g e r y 14 .2 14.2 O r t h o p e d i c su r ge ry 11 .0 10.3 U r o l o g i c a l s u r ge ry 9 .0 8.5 P l a s t i c s u r ge ry 8 .9 8.2 D i a g n o s t i c endoscopy 7 .9 6.6 Ophthalmology 6 .0 6.7 Other 10 .2 11.2 T o t a l 100 .0 100. Cases 9,047 12,638 x> Source : Robinson GC, C l a r k e HF: The H o s p i t a l Care of C h i l d r e n . A rev iew of contemporary i s s u e s . New York , Oxford U n i v e r s i t y P r e s s , 1980 (p. 119). 2> Source : B.C. M i n i s t r y of H e a l t h , H o s p i t a l Programs, A d m i s s i o n - s e p a r a t i o n database f o r day c a r e s u r g e r y . 35 T a b l e 3. Ten Most Common Day Care Su rge ry P rocedures i n P a e d i a t r i c (0-14) Age Group i n B.C. i n 1976 and 1982/83 Op. code OPERATIVE PROCEDURE % of t o t a l YEAR 1 9 7 6 x : 17.0 Myringotomy 20.0 99.9 Other d e n t a l s u r ge ry o p e r a t i o n s 6.8 A4.6 Cys to scopy and u r e t h r o s c o p y 6.8 99.3 E x t r a c t i o n of t o o t h , f o r c e p s 5.7 92.1 L o c a l e x c i s i o n of l e s i o n o f s k i n and subcutaneous t i s s u e 4.7 61.2 C i r c u m c i s i o n 4.0 88.9 Other ops . on musc le , tendon f a s c i a , and bur sa 3.2 21.3 Adenoidectomy w i thou t t o n s i l l e c t o m y 2.7 17.9 Other o p e r a t i o n s on m idd le ea r 2.5 06.5 P r o b i n g o f l a c r i m a l duc t 2.2 T o t a l number o f cases 9,047 YEAR 1 9 8 2 / 8 3 2 : 32.01 Myringotomy w i t h i n s e r t i o n of tube 25.4 01.34 Other nonopera t i ve c y s t o s copy 6.6 35.20 R e s t o r a t i o n of t o o t h by f i l l i n g 6.2 76.00 C i r c u m c i s i o n 5.1 40.50 Adenoidectomy w i thout t o n s i l l e c t o m y 3.8 07.29 Other f o r c i b l e c o r r e c t i o n o f d e f o r m i t y 3.5 98.12 L o c a l e x c i s i o n , o r d e s t r u c t i o n of l e s i o n o r t i s s u e of s k i n and subcutaneous t i s s u e 2.6 35.19 Other s u r c i c a l e x t r a c t i o n of t o o t h 2.5 35.09 Forceps e x t r a c t i o n o f o t h e r t o o t h 2.5 91.01 C l o s e d r e d u c t i o n of f r a c t u r e (wi thout i n t e r n a l f i x a t i o n ) - r a d i u s and u l n a 2.5 T o t a l number of cases 12,638 x> Sou rce : Robinson GC, C l a r k e HF: The H o s p i t a l Care of C h i l d r e n . A Review of contemporary i s s u e s . New York , Ox fo rd U n i v e r s i t y P r e s s , 1980 (p. 120-121) . O p e r a t i v e codes r e f e r t o the e i g h t r e v i s i o n of I n t e r n a t i o n a l C l a s s i f i c a t i o n of D i s e a s e s . 2> Source : B.C. M i n i s t r y o f H e a l t h , H o s p i t a l Programs, A d m i s s i o n - s e p a r a t i o n database f o r day c a r e s u r g e r y . O p e r a t i v e codes r e f e r t o the Canadian C l a s s i f i c a t i o n o f D i a g n o s t i c , T h e r a p e u t i c , and S u r g i c a l P r o c e d u r e s . 36 2) Cost s t u d i e s i n the U n i t e d S t a t e s a r e m a i n l y based on charges . I n s o f a r as c o s t s a re a c c u r a t e l y r e f l e c t e d i n charges f o r h o s p i t a l s e r v i c e s , the economic sav ings r e s u l t i n g from day c a r e s u r g e r y on a p e r - c a s e - t r e a t e d b a s i s a r e v e r y s i g n i f i c a n t , r unn ing from 25 to 60 p e r c e n t o f t o t a l i n p a t i e n t cha rges . 3) Charges do n o t , i n g e n e r a l , a c c u r a t e l y r e f l e c t c o s t s . There seems t o be a tendency to o v e r e s t i m a t e day ca re su r ge ry charges and cover d e f i c i t s i n l e s s p r o f i t a b l e areas w i t h p r o f i t s made on day c a r e s u r g e r y . 4) There a re o n l y a few s t u d i e s a t t empt i n g a s e r i o u s and d e t a i l e d c o s t a n a l y s i s i n s t e a d of r e l y i n g on h o s p i t a l charges o r p e r diem c o s t s . 5) Sav ings from day ca re su r ge ry do not a r i s e mere ly from sav ings of " h o t e l " c o s t s on the n u r s i n g wards but a l s o from r e d u c t i o n of h o s p i t a l - a c q u i r e d p o s t -o p e r a t i v e i n f e c t i o n s and r e d u c t i o n of unnecessary d i a g n o s t i c t e s t i n g . 37 6) The q u e s t i o n of whether day ca re s u r g e r y a c t u a l l y reduces expenses on a t o t a l b a s i s o r whether i t mere l y lowers u n i t c o s t s o r p e r - p a t i e n t c o s t s remains u n c l e a r . Berk and Chalmers (1981) rev iewed 109 s t u d i e s comparing ambu la tory and i n p a t i e n t c a re w i t h r e g a r d t o c l i n i c a l outcome o r c o s t . A l l but 31 of the 109 s t u d i e s ment ioned economic outcome. A l though most f a vo red ambulatory c a r e over i n p a t i e n t c a r e , o n l y two of the s t u d i e s had used a p p r o p r i a t e measurements of the c o s t of r e s o u r c e s u sed . Evans and Robinson (1973) c a r r i e d out a d e t a i l e d c o s t compar i son o f day ca re su r ge ry and t r a d i t i o n a l i n p a t i e n t ca re u s i n g 1970 da ta from the C h i l d r e n ' s H o s p i t a l i n Vancouver . They used step-down c o s t a n a l y s i s t o i s o l a t e the f u l l y -a l l o c a t e d l o n g - r u n c o s t s per ep i sode of c a r e . The s tudy showed t h a t a day ca re su r ge ry ep i sode c o s t s about h a l f t h a t of matched p a t i e n t s w i t h s i m i l a r t rea tment on the i n p a t i e n t wards. R e p l i c a t i o n of t h i s a n a l y s i s w i t h 1975 da ta con f i rmed the r e s u l t ; p o t e n t i a l t o t a l sav ings pe r ep i sode were 50-70 p e r c e n t (Evans e t a 1 . f 1978). In o r d e r t o conc lude t h a t lower u n i t c o s t s of day c a r e s u r g e r y w i l l be t r a n s l a t e d i n t o sav ings i n t o t a l h e a l t h c a re e x p e n d i t u r e s , one must make an assumpt ion t h a t beds f r e e d by s u b s t i t u t i o n of day ca re f o r i n p a t i e n t c a r e w i l l not be f i l l e d 38 by o t h e r c a se s . Yost (1976), f o r example, s t r e s s e s t h a t p o t e n t i a l sav ings can e a s i l y be d i s s i p a t e d i n c o s t add-ons i f the r a t e of performance of s u r g i c a l p rocedures shou ld r i s e w i t h the a v a i l a b i l i t y o f new f a c i l i t i e s . Goran and Donaldson (1976) p o i n t out t h a t i f unnecessary i n p a t i e n t beds a re not c l o s e d o r c o n v e r t e d , h o s p i t a l s u r g i c a l p rocedures can e a s i l y r i s e i f p rocedures a re s h i f t e d from the p h y s i c i a n ' s o r d e n t i s t ' s o f f i c e o r generated de novo in cases where s u r g i c a l i n t e r v e n t i o n i s o n l y m a r g i n a l l y j u s t i f i e d . Downey (1976) makes the same p o i n t about the need to shut h o s p i t a l s i f p o t e n t i a l sav ings a re to be r e a l i z e d . Rennie (1977) w r i t e s i n the Canadian con tex t t h a t "day ca re su r ge ry c o n s t i t u t e s a p o t e n t i a l sav ings to the h e a l t h d e l i v e r y system where i t i s e i t h e r a s u b s t i t u t e f o r i n p a t i e n t c a r e w i t h the i n p a t i e n t care f a c i l i t y a c t u a l l y taken out of s e r v i c e , o r where i t r e p r e s e n t s a l e s s c o s t l y a l t e r n a t i v e to c a p i t a l inves tment and a d d i t i o n a l o p e r a t i n g c o s t s under those c o n d i t i o n s where the government i s p repa red t o expand f a c i l i t i e s i n an under-bedded community. In t h i s l a s t i n s t a n c e , an add-on c o s t i s g e n e r a t e d , but l e s s than would be the case w i t h add ing on an a d d i t i o n a l i n p a t i e n t f a c i l i t y " (Rennie, 1977, p .26 ) . He argues t h a t u n l e s s these s p e c i f i c t r a d e - o f f s a re acknowledged by government, the ambu la tory c a re program s imp ly becomes an add -on , i n c r e a s i n g the th rough -pu t o f p a t i e n t s w i th no o f f s e t t i n g d o l l a r t r a n s f e r . Response of use of i n p a t i e n t c a r e to day ca re s u r g e r y , o t h e r t h i n g s be ing e q u a l , becomes o f utmost 39 importance i n making the f i n a l c o n c l u s i o n on the economic advantages of day ca re su r ge ry . 2.4. Response o f i n p a t i e n t u t i l i z a t i o n t o day c a r e s u r g e r y There a r e v e r y few p u b l i s h e d s t u d i e s on the r e l a t i o n s h i p between day c a r e s u r g e r y and i n p a t i e n t u t i l i z a t i o n . Evans and Robinson (1973) t r i e d t o approach t h i s problem by r e v i e w i n g the work loads of s p e c i f i c surgeons pe r f o rm ing day ca re s u r g i c a l p rocedures a t C h i l d r e n ' s H o s p i t a l . They conc luded t h a t a s i g n i f i c a n t p r o p o r t i o n (about 24 p e r c e n t ) of the day c a r e s u r g e r y cases were new g e n e r a t i o n , which would not have been c a r e d f o r a t the h o s p i t a l i f the day c a r e s u r g e r y had not been a v a i l a b l e . However, t h e i r s tudy approach i s s u b j e c t t o many con found ing f a c t o r s , and as they r i g h t l y warn, the g e n e r a t i o n may r e p r e s e n t t r a n s f e r s from o t h e r h o s p i t a l s and the s u b s t i t u t i o n f o r i n p a t i e n t c a r e c o u l d have taken p l a c e a t the r e g i o n a l l e v e l . A l a t e r s tudy examined the r e l a t i o n s h i p of day c a r e su r ge ry and i n p a t i e n t u t i l i z a t i o n a t the r e g i o n a l h o s p i t a l d i s t r i c t l e v e l (Evans e t a 1. f 1978; Evans and Rob inson, 1980). Trends i n i n p a t i e n t p a e d i a t r i c s u r g i c a l p rocedures over t ime were compared t o c o r r e s p o n d i n g t rends i n day c a r e s u r g e r y , i n the G r e a t e r Vancouver Reg i ona l d i s t r i c t e x c l u d i n g r e f e r r a l s from o t h e r r e g i o n s . There was a marked dec rease i n i n p a t i e n t s u r g e r y c o i n c i d i n g w i t h an i n c r e a s e i n day c a r e s u r g e r y . 40 However, the drop i n i n p a t i e n t su r ge ry i n the r e g i o n was much l a r g e r than c o u l d be accounted f o r by the i n c r e a s e i n s u r g i c a l day c a r e . The drop was l a r g e l y due t o the dec rea se o f more than two t h i r d s over the decade from 1968 t o 1978 i n the r a t e o f per formance o f t o n s i l l e c t o m y and adenoidectomy. The au thor s suggested t h a t t h i s dec rea se c o u l d not be a t t r i b u t e d t o the i n c r e a s e i n s u r g i c a l day ca re because the o p e r a t i o n i s one t h a t had been judged i n a p p r o p r i a t e f o r s u r g i c a l day ca re i n a lmost a l l the h o s p i t a l s p r o v i d i n g t h i s form of c a r e . When t o n s i l l e c t o m i e s and adeno idectomies were exc luded from the i n p a t i e n t da ta the r e s i d u a l i n p a t i e n t su r ge ry t r e n d showed a much l e s s marked d e c l i n e . Dur ing the p e r i o d 1967-71, when s u r g i c a l day ca re was most r a p i d l y i n t r o d u c e d i n the r e g i o n , t h e r e was an a lmost commensurate i n c r e a s e i n the performance of a l l p a e d i a t r i c s u r g i c a l p rocedures ( i n p a t i e n t and day c a r e ) , but the performance of i n p a t i e n t s u r g i c a l p r o c e d u r e s , e x c l u d i n g t o n s i l l e c t o m y , was v i r t u a l l y unchanged. The s tudy suggested t h a t the main impact of day ca re s u r g e r y had been to expand the t o t a l volume of s u r ge ry , a l though some (but r e l a t i v e l y l i t t l e ) s u b s t i t u t i o n f o r i n p a t i e n t c a re c o u l d have a l s o o c c u r r e d . T h i s i n t e r p r e t a t i o n , however, depended on the assumpt ion t h a t i n the absence of day ca re s u r g e r y , o v e r a l l s u r g i c a l u t i l i z a t i o n i n the r e g i o n would not have changed. There i s the p o s s i b i l i t y of s h i f t s i n o p e r a t i v e p rocedures o r the s u r g i c a l p a t t e r n of p r a c t i c e which c o u l d have l e d t o g r e a t e r s u r g i c a l a c t i v i t y c o i n c i d e n t w i t h , though not caused by, the a v a i l a b i l i t y o f day ca re su r ge ry . In the se 41 c i r c u m s t a n c e s , i n p a t i e n t h o s p i t a l u t i l i z a t i o n m i g h t h a v e i n c r e a s e d s h a r p l y h a d d a y c a r e s u r g e r y n o t b e e n a v a i l a b l e . I n o r d e r t o c o n t r o l f o r t h e a b o v e p o s s i b i l i t y , E v a n s et. a l . (1983) c o n d u c t e d a n o t h e r s t u d y i n a t o t a l p o p u l a t i o n u s i n g p r o v i n c e - w i d e d a t a a n d a " m o d e l " o f t h e f a c t o r s a f f e c t i n g s u r g i c a l a n d m e d i c a l i n p a t i e n t u s e . A l t h o u g h i t i s i m p o s s i b l e t o k n o w w h a t s u r g i c a l o r t o t a l h o s p i t a l u s e w o u l d h a v e b e e n i n t h e a b s e n c e o f d a y c a r e s u r g e r y , i t i s p o s s i b l e t o c o n t r o l t h e e f f e c t o f k n o w n a n d some o f t h e u n k n o w n d e t e r m i n a n t s o f i n p a t i e n t u t i l i z a t i o n a n d e x a m i n e t h e r e l a t i o n s h i p o f d a y c a r e s u r g e r y a n d i n p a t i e n t u t i l i z a t i o n , o t h e r t h i n g s b e i n g e q u a l . T h e d a t a b a s e f o r t h i s r e c e n t s t u d y c o n s i s t e d o f a n u m b e r o f r e g i o n s (75 s c h o o l d i s t r i c t s ) a n d y e a r s (1968-1976). F o r e a c h d i s t r i c t a n d y e a r , a g e - s e x a d j u s t e d ( t o p r o v i n c i a l a g e a n d s e x m i x ) r a t e s o f u t i l i z a t i o n o f i n p a t i e n t h o s p i t a l c a r e ( n e t o f m a t e r n i t y a n d l o n g - t e r m c a r e ) a n d o f d a y c a r e u t i l i z a t i o n w e r e c o m p u t e d . I n a d d i t i o n , a c a p a c i t y m e a s u r e o f b e d s r e f l e c t i n g a c t u a l b e d u s e e v e r y w h e r e i n t h e p r o v i n c e w a s c a l c u l a t e d f o r e a c h s c h o o l d i s t r i c t . T h e p r i n c i p a l f o c u s o f t h e s t u d y w a s t h e r e l a t i o n s h i p b e t w e e n t w o v a r i a b l e s - t h e e x t e n t ( i f a n y ) o f a s s o c i a t i o n b e t w e e n d a y c a r e s u r g e r y u t i l i z a t i o n a n d r e d u c e d i n p a t i e n t u s e . T h e c o m b i n e d c r o s s - d i s t r i c t c r o s s - y e a r s t u d y d e s i g n p e r m i t t e d c o n t r o l o f b o t h r e g i o n a l a n d t i m e -d e p e n d e n t c o n f o u n d i n g e f f e c t s s u c h a s s h i f t s i n m e d i c a l t e c h n o l o g y a n d s u r g i c a l p r a c t i c e . T h e d e p e n d e n t v a r i a b l e s 42 were a s e r i e s of i n c r e a s i n g l y day c a r e e l i g i b l e measures of i n p a t i e n t u t i l i z a t i o n . Independent v a r i a b l e s were i n p a t i e n t bed c a p a c i t y (hypo thes i zed to i n c r e a s e i n p a t i e n t use and d e c r e a s e day ca re su r ge ry u s e ) , s oc i o -economic s t a t u s of each s c h o o l d i s t r i c t p o p u l a t i o n , and the numbers, types and a c t i v i t y l e v e l s of p h y s i c i a n s i n each s c h o o l d i s t r i c t . M u l t i v a r i a t e a n a l y s i s o f the da ta demonstrated s u b s t i t u t i o n i n the range of 30-40 p e r c e n t of day ca re su r ge ry r e p r e s e n t i n g " s aved " i n p a t i e n t c a s e s ; but 60-70 p e r c e n t of day c a r e su r ge ry r e p r e s e n t e d g e n e r a t i o n of new a c t i v i t y f o r the h o s p i t a l system as a whole. Moreover, the a v a i l a b i l i t y of day c a r e su r ge ry f a c i l i t i e s had no e f f e c t on o v e r a l l t o t a l m e d i c a l and s u r g i c a l i n p a t i e n t u t i l i z a t i o n , as the space " saved" by day c a r e s u r g e r y - t y p e cases was f i l l e d i n by o t h e r s . The d r i v i n g f o r c e beh ind i n p a t i e n t use was bed a v a i l a b i l i t y and t o a l e s s e r e x t e n t s oc i o -economic v a r i a b l e s . The number of p h y s i c i a n s pe r ns. was not shown to have any e f f e c t on i n p a t i e n t s u r g i c a l u t i l i z a t i o n (Evans e t a l . f 1983 ) . There a re no s t u d i e s t h a t a l l o w d i r e c t e x t r a p o l a t i o n of the r e s u l t s i n the t o t a l p o p u l a t i o n t o a c h i l d p o p u l a t i o n . P a e d i a t r i c i a n s argue t h a t p a e d i a t r i c c a re i s d i f f e r e n t from a d u l t c a r e i n r e s p e c t t o tendency t o h o s p i t a l i z e . Net s u b s t i t u t i o n e f f e c t may be h i g h e r i n the p a e d i a t r i c age group than i n the t o t a l p o p u l a t i o n . A l s o , the s tudy by Evans e t a1 . (1983) took p l a c e i n a p e r i o d of i n c r e a s i n g o r s teady bed c a p a c i t y . P a e d i a t r i c and a d u l t h o s p i t a l bed c a p a c i t y i n B.C. 43 f e l l i n the second h a l f o f the 1970s and i n the e a r l y 1980s. From a p o l i c y p e r s p e c t i v e i t i s impor tant t o know how t h i s p o l i c y change i n r e s p e c t t o bed c a p a c i t y may have a l t e r e d the r e l a t i o n s h i p between day ca re su r ge ry a v a i l a b i l i t y and i n p a t i e n t u t i l i z a t i o n . 2.5. The r o l e o f i n p a t i e n t bed s u p p l y - Roemer 's Law 2 . 5 . 1 . E v o l u t i o n o f Roemer's Law When h o s p i t a l s e r v i c e s were, i n the main, p r i v a t e l y pu rcha sed , h o s p i t a l u t i l i z a t i o n r e s e a r c h was c e n t r e d on f a c t o r s t h a t were r e l a t e d to low u t i l i z a t i o n . Study a f t e r s tudy i n the 1930s and the e a r l y 1940s showed t h a t , except f o r the v e r y poor and f o r p u b l i c a s s i s t a n c e r e c i p i e n t s , whose ca re was s u b s i d i z e d by p h i l a n t h r o p y and p u b l i c funds , the volume of h o s p i t a l s e r v i c e s r e c e i v e d v a r i e d i n d i r e c t p r o p o r t i o n to f a m i l y income ( H o i l i n g s w o r t h e t a 1. f 1947). The i n t r o d u c t i o n of h o s p i t a l i n s u r a n c e w i t h a c o i n c i d i n g i n c r e a s e i n h o s p i t a l u t i l i z a t i o n s h i f t e d the r e s e a r c h emphasis onto f a c t o r s t h a t seemed t o u n d e r l i e the h i gh u t i l i z a t i o n of h o s p i t a l s . In the l a t e 1950s Roemer and Sha in (1959) summarized the knowledge of h o s p i t a l u t i l i z a t i o n d e t e r m i n a n t s . They suggested t h a t the supp ly of beds a v a i l a b l e t o the p o p u l a t i o n i s the most fundamental of a l l the de terminant s of h o s p i t a l u t i l i z a t i o n a r i s i n g from the p a t i e n t , the h o s p i t a l , o r the 44 d o c t o r . T h e i r t h e o r y , a t t h a t t ime , was m a i n l y based on c r o s s - s e c t i o n a l s t u d i e s . Us ing 1957 da ta on bed s u p p l y p e r thousand p o p u l a t i o n and h o s p i t a l u t i l i z a t i o n r a t e s f o r the U n i t e d S t a t e s and f o r the c o u n t i e s of u p s t a t e New York , Sha in and Roemer (1959) demonstrated a h i gh c o r r e l a t i o n between bed s u p p l y and h o s p i t a l u t i l i z a t i o n , sugge s t i ng t h a t more than 7 0 p e r c e n t of the d i f f e r e n c e s i n h o s p i t a l u t i l i z a t i o n by s t a t e and by county were a s s o c i a t e d w i t h d i f f e r e n c e s i n bed supp l y . They ran the same ana l y se s w i t h da ta from 1940 when t h e r e was no boom i n incomes and h o s p i t a l i n s u r a n c e , f i n d i n g the same h i g h r e l a t i o n s h i p . T h e i r s tudy a l s o showed t h a t t h e r e was v i r t u a l l y no r e l a t i o n s h i p between the supp l y of beds and h o s p i t a l occupancy. On ly 4 p e r c e n t of the v a r i a t i o n i n average occupancy r a t e s from s t a t e t o s t a t e c o u l d be a t t r i b u t e d t o d i f f e r e n c e s i n bed supp l y . In a d d i t i o n to the e f f e c t of bed supp l y i n p l a c i n g a c e i l i n g on u t i l i z a t i o n r a t e s , i t was suggested t h a t the bed supp l y l i k e w i s e tends to s e t a f l o o r on u t i l i z a t i o n (Roemer and S h a i n , 1959). I f a community has a r e l a t i v e l y low supp ly of beds , p h y s i c i a n s w i l l admit p a t i e n t s who a re s e r i o u s l y i l l . I f the bed supp l y i s i n c r e a s e d , p h y s i c i a n s w i l l tend t o admit p a t i e n t s who were f o r m e r l y o f lower p r i o r i t y , p a t i e n t s w i t h l e s s s e r i o u s i l l n e s s , s u r g i c a l cases of an e l e c t i v e n a t u r e , e t c . (Roemer and S h a i n , 1959 ) . A l r e a d y b e f o r e the work by Sha in and Roemer (1959), Myers (1954) i n Saskatchewan had demonstrated the r e l a t i o n s h i p 45 between h o s p i t a l u t i l i z a t i o n and supp l y of beds. He showed t h a t the volume of cases con t i nued t o r i s e even when the supp l y of h o s p i t a l beds was w e l l above the l o c a l l y recommended l e v e l o f 7.5 pe r 1,000, which a l r e a d y was an e x c e p t i o n a l l y h i g h b e d - t o - p o p u l a t i o n r a t i o . T h i s Saskatchewan s tudy a l s o r e v e a l e d a d i r e c t r e l a t i o n s h i p between r a t e s of s u r g i c a l o p e r a t i o n s and the supp l y of h o s p i t a l beds . A subsequent s tudy i n Saskatchewan con f i rmed t h a t i n the a reas o f h i gh u t i l i z a t i o n and h i gh h o s p i t a l bed c a p a c i t y t h e r e tended t o be more f r e q u e n t admis s ion of minor cases which r e q u i r e d s h o r t e r h o s p i t a l s t a y . A l s o , the readmi s s i on r a t e s were found to be h i g h e r i n the se same areas (Roth e t a 1. f 1955). So f a r , the ev i dence on bed supp l y e f f e c t was based on c r o s s - s e c t i o n a l s t u d i e s , but i n 1961 Roemer p u b l i s h e d a l o n g i t u d i n a l s tudy c o n f i r m i n g what had been a l r e a d y found i n the p r e v i o u s s t u d i e s . T h i s seemed to ensure a g e n e r a l a ccep tance o f the r e l a t i o n s h i p between bed supp l y and h o s p i t a l u t i l i z a t i o n . Roemer (1961) demonstrated t h a t the i n c r e a s e i n h o s p i t a l u t i l i z a t i o n when bed supp l y was i n c r e a s e d was due to changes t h a t the i n c r e a s e d bed supp l y caused i n the m e d i c a l p o l i c i e s of l o c a l p h y s i c i a n s . There was s i m p l y an i n c r e a s e d tendency t o h o s p i t a l i z e p a t i e n t s i n the g i v e n p o p u l a t i o n , w i thou t any ev i dence of a co r re spond ing i n c r e a s e i n the i n c i d e n c e of i l l n e s s . He suggested t h a t any e f f e c t i v e c o n t r o l over the u t i l i z a t i o n r a t e of h o s p i t a l s shou ld r e s t f i r s t of a l l on some s o r t of c o n t r o l over the supp l y of beds. 46 2 .5 .2 . Que s t i on o f c a u s a l i t y A l though t h e r e i s g e n e r a l agreement t h a t bed supp l y i s r e l a t e d t o h o s p i t a l u t i l i z a t i o n , the i n t e r p r e t a t i o n o f t h i s r e l a t i o n s h i p i s s t i l l a rgued. There a re a t l e a s t two a l t e r n a t i v e ways of i n t e r p r e t i n g t h i s r e l a t i o n s h i p : 1) the r e l a t i o n s h i p i s c a u s a l , as Roemer suggests ; o r 2) the r e l a t i o n s h i p i s s pu r i ou s i n t h a t an an tecedent v a r i a b l e i s c a u s a l l y r e l a t e d t o both supp ly and u t i l i z a t i o n . Those who see the r e l a t i o n s h i p as s pu r i ou s g e n e r a l l y c l a i m t h a t both h o s p i t a l u t i l i z a t i o n and bed c a p a c i t y a re determined by unmet demand o r need f o r h o s p i t a l s e r v i c e s . Unmet need causes i n c r e a s e i n supp l y of beds and more h o s p i t a l u t i l i z a t i o n once beds a r e s u p p l i e d . A c c o r d i n g t o c l a s s i c economic t h e o r y of supp l y and demand, supp l y does not j u s t appear . I t a r i s e s as a response to a number of p r e s s u r e s , one of which c o u l d be the demand f o r f a c i l i t i e s . I f demand f o r f a c i l i t i e s e x i s t s , the f a c t o r s t h a t a f f e c t demand would a l s o genera te p r e s s u r e t o a f f e c t supp l y (Ro sen tha l , 1964). T h i s argument runs i n t o prob lems, when bed supp ly l e v e l s a r e compared t o i l l n e s s needs. One has o n l y t o compare b e d - t o -p o p u l a t i o n r a t i o s between d e v e l o p i n g c o u n t r i e s and Western n a t i o n s to be reminded of the r e l a t i v e l y minor impact of i l l n e s s need on the supp ly of beds (Roemer and S h a i n , 1959). A l though compar ison of d i f f e r e n t areas w i t h i n Western c o u n t r i e s w i t h r e s p e c t t o i l l n e s s l e v e l and bed supp l y may not 47 y i e l d such d ramat i c c o n t r a s t s , economic s t a t u s of an a rea would p r o b a b l y s t i l l outweigh the i n c i d e n c e o f i l l n e s s as a de te rminant of bed c a p a c i t y . C o n s t r u c t i o n of a h o s p i t a l i s i n c r e a s i n g l y a p o l i t i c a l d e c i s i o n s which i s i n f l u e n c e d by s e v e r a l n o n - h e a l t h r e l a t e d f a c t o r s . O f ten i t i s the e f f e c t i v e demand of "buy ing power" f o r beds which i s d e c i s i v e , and t h i s has l i t t l e r e l a t i o n s h i p t o i l l n e s s need. E c o n o m i c a l l y w e l l - o f f communit ies have u s u a l l y more p o l i t i c a l weight when h o s p i t a l r e s o u r c e s a r e d i s t r i b u t e d . I f i l l n e s s need i s the impetus f o r bed supp l y one would expect t o see a decrease i n bed c a p a c i t y and c l o s u r e s of h o s p i t a l s w i t h improv ing h e a l t h s t a t u s of the p o p u l a t i o n . However, t h i s has a lmost never happened. Downs iz ing the h o s p i t a l s e c t o r i n B.C. i n the l a t e 1970s and the e a r l y 1980s was not a mat te r o f re spond ing to a dec rea se i n i n c i d e n c e of d i s e a s e s , but a d e c i s i o n t o c o n t a i n c o s t s . Suppor te r s of the c a u s a l t h e o r y can be d i v i d e d i n t o those who s t i l l r e l y on the c l a s s i c t h e o r y o f supp l y and demand and e x p l a i n the Roemer e f f e c t through a t ime p r i c e mechanism, and those who b e l i e v e t h a t supp l y c r e a t e s i t s own demand. In t h e o r y , an i n c r e a s e i n supp ly of h o s p i t a l beds se rves to depres s the money p r i c e of h o s p i t a l s e r v i c e s r e s u l t i n g i n an i n c r e a s e i n the q u a n t i t y of c a re demanded a t the p r e v a i l i n g lower p r i c e s . However, t h i s c o u l d not be the e x p l a n a t i o n of Roemer's Law i n a " f r e e c a r e " s i t u a t i o n such as Canada. On 48 the o t h e r hand, i t has been suggested t h a t an i n c r e a s e i n bed supp l y may cause a r e d u c t i o n i n w a i t i n g t imes f o r t r e a t m e n t , make p o s s i b l e e a r l i e r admiss ions t o h o s p i t a l s , and i n g e n e r a l reduce the amount of t ime i n v o l v e d i n o b t a i n i n g c a r e . I f a l l money p r i c e s throughout the economy were h e l d con s t an t and o n l y the adjustment d e s c r i b e d were a l l owed t o take p l a c e , the r e s u l t would be a r e l a t i v e decrease i n the t o t a l " p r i c e " of h e a l t h c a r e v i s - a - v i s o t h e r goods and s e r v i c e s and an observed i n c r e a s e i n u t i l i z a t i o n . May (1975) c o n t r o l l e d both money and t ime p r i c e v a r i a b l e s w h i l e examining the r e l a t i o n s h i p between bed supp l y and h o s p i t a l u t i l i z a t i o n i n a s tudy u s i n g su rvey d a t a . The e l a s t i c i t y of h o s p i t a l admiss ions w i t h r e s p e c t t o h o s p i t a l beds was found to be .22. T h i s i s l e s s than i n s t u d i e s t h a t have om i t ted t ime p r i c e s (G insburg and K o r e t z , 1983) s u g g e s t i n g t h a t a t ime p r i c e mechanism may p l a y a r o l e i n Roemer e f f e c t . The o t h e r s c h o o l of h e a l t h economists who b e l i e v e i n a c a u s a l bed e f f e c t argue t h a t c o n v e n t i o n a l laws of s upp l y and demand p l a y l i t t l e r o l e i n h e a l t h c a re u t i l i z a t i o n because of the p e c u l i a r r e l a t i o n s h i p between the h e a l t h c a r e consumer and h e a l t h c a r e consumpt ion. The major d e c i s i o n s c o n c e r n i n g consumption a re made not by the consumer, but the p r o v i d e r . They argue t h a t the c a u s a l e f f e c t of bed supp l y on h o s p i t a l u t i l i z a t i o n works through the way i n which p h y s i c i a n s 49 p r a c t i c e . An i n c r e a s e i n the g e n e r a l h o s p i t a l bed supply a v a i l a b l e t o a p h y s i c i a n a l t e r s the way she p r o v i d e s medical c a r e , which i n t u r n i n c r e a s e s the r a t e a t which t h i s s upply i s u t i l i z e d . In o t h e r words, i n s t e a d of s h i f t i n g the demand f o r h o s p i t a l s e r v i c e s along the demand curve, an i n c r e a s e i n the sup p l y of beds w i l l prompt a s h i f t i n the 'demand' schedule i t s e l f (although the demand schedule cannot, then, be i n t e r p r e t e d i n the c o n v e n t i o n a l manner as r e p r e s e n t a t i o n of consumers' f u l l y - i n f o r m e d responses t o d i f f e r e n t h o s p i t a l care p r i c e s ) . The standard method of a s s e s s i n g the v a l i d i t y of Roemer's Law has been t o use m u l t i p l e r e g r e s s i o n a n a l y s i s t o examine r e l a t i o n s h i p s between use - u s u a l l y days of h o s p i t a l i z a t i o n per c a p i t a - and demographic v a r i a b l e s , h e a l t h s t a t u s , the p r i c e of h o s p i t a l s e r v i c e s (net of i n s u r a n c e ) , and v a r i a b l e s r e f l e c t i n g the a v a i l a b i l i t y of medical r e s o u r c e s (Ro, 1969; F e l d s t e i n , 1971; Anderson, 1973; H a r r i s , 1975a; Van der Gaag et a 1 ., 1975). The u n d e r l y i n g assumption i s t h a t i f bed a v a i l a b i l i t y e f f e c t i s s p u r i o u s , then the r e l a t i o n s h i p between sup p l y and use should disappear when confounding v a r i a b l e s are ente r e d i n t o the a n a l y s i s . I f i t does not di s a p p e a r , then the r e g r e s s i o n c o e f f i c i e n t of the h o s p i t a l bed v a r i a b l e p r o v i d e s a measure of the Roemer e f f e c t . 5 0 Ginsburg and K o r e t z (1983) have noted the problems i n h e r e n t i n the da t a used by many s t u d i e s . They l i s t the f o l l o w i n g s tudy prob lems: a) Tncorrect measurement of the price of services. A p p r o p r i a t e measure of the p r i c e of s e r v i c e s shou ld be the marg ina l p r i c e minus i n s u r a n c e reimbursement - t h a t i s . the net p r i c e to the p a t i e n t of an e x t r a day o r an e x t r a s t a y i n the h o s p i t a l . b) Tncorreot measurement of the nt.i l i g a t i o n rate. Numerator and denominator of the u t i l i z a t i o n r a t e shou ld r e f e r t o the same market a r e a . O f ten days of h o s p i t a l c a re (the numerator) r e f l e c t s s e r v i c e s d e l i v e r e d by a rea h o s p i t a l s t o both r e s i d e n t s and n o n r e s i d e n t s a l i k e , but p o p u l a t i o n (the denominator) r e f l e c t s o n l y the r e s i d e n t s of the a r e a . Areas w i th many beds pe r c a p i t a tend t o have o v e r s t a t e d u t i l i z a t i o n r a t e s c au s i n g an upward b i a s i n e s t ima te s of the Roemer e f f e c t . c) Omission of important variables. The omi s s i on of i n f o r m a t i o n on h e a l t h s t a t u s tends t o b i a s e s t imate s o f the Roemer e f f e c t upward s i n c e poor h e a l t h s t a t u s i n an a rea tends t o produce both h i g h e r u t i l i z a t i o n and"a l a r g e r supp l y of beds . 51 d) S imultaneous equat ion b i a s . Wh i le bed supp l y may determine u t i l i z a t i o n , t h e o r y a l s o suggests t h a t over the l ong r u n , u t i l i z a t i o n shou ld determine bed supp l y . Beds per c a p i t a i s f u l l y exogenous o n l y i n the sho r t r u n . O r d i n a r y l e a s t squares e s t i m a t i o n c o u l d r e s u l t i n an upward b i a s of the e s t i m a t e of the Roemer e f f e c t . G in sburg and Ko re tz (1983) overcame these prob lems, f o r example, by i n c l u d i n g a t h r e e - y e a r lagged v a l u e of the dependent v a r i a b l e as a proxy f o r unmeasured v a r i a b l e s t h a t might a f f e c t u t i l i z a t i o n and by e n t e r i n g beds pe r c a p i t a as a f i r s t d i f f e r e n c e . G iven l ong l ag s i n bed c o n s t r u c t i o n , i t was u n l i k e l y t h a t the change i n beds was i n f l u e n c e d by the change i n u t i l i z a t i o n f o r the same t ime p e r i o d . T h e i r s tudy d e s i g n was v e r y s i m i l a r t o the one t h a t H a r r i s (1975b) had used e a r l i e r . Both H a r r i s and G insburg and K o r e t z demonstrated a h i g h l y s i g n i f i c a n t Roemer e f f e c t . 2 .5 .3 . The Roemer e f f e c t i n p a e d i a t r i c p o p u l a t i o n s There a re v e r y few s t u d i e s on a bed a v a i l a b i l i t y e f f e c t i n p a e d i a t r i c c a r e , but they a l l seem to i n d i c a t e lower response o f h o s p i t a l use to bed supp l y than i n the a d u l t p o p u l a t i o n (Van d e r Gaag e t a 1. f 1975; C o n n e l l e t a l . . 1981). 52 Van d e r Gaag e t a l . (1975) a n a l y z e d the e f f e c t o f number o f g e n e r a l h o s p i t a l beds and number o f g e n e r a l p r a c t i t i o n e r s per 1,000 p o p u l a t i o n on h o s p i t a l a d m i s s i o n r a t e by age -group u s i n g c r o s s - s e c t i o n a l d a t a from 44 s e r v i c e areas i n the N e t h e r l a n d s . A l t h o u g h bed a v a i l a b i l i t y was p o s i t i v e l y r e l a t e d to a d m i s s i o n r a t e s i n p a e d i a t r i c age g r o u p s , the e l a s t i c i t i e s were c l e a r l y lower than i n the a d u l t group w i t h the e x c e p t i o n o f i n f a n t s and newborns. A l s o , the e x p l a n a t o r y power o f bed and p h y s i c i a n c a p a c i t y was l e s s than f o r the a d u l t p o p u l a t i o n . An at tempt t o i n c l u d e o t h e r h e a l t h c a r e r e s o u r c e v a r i a b l e s and p o p u l a t i o n c h a r a c t e r i s t i c s i n the r e g r e s s i o n e q u a t i o n d i d not work: the c o e f f i c i e n t s o f most v a r i a b l e s were n o n s i g n i f i c a n t o r u n i n t e r p r e t a b l e . The authors s t a t e d t h a t a d m i s s i o n s f o r the lower age groups a r e not a d e q u a t e l y e x p l a i n e d by the e i g h t exogenous v a r i a b l e s used (bed c a p a c i t y , number o f a d m i s s i o n s i n u n i v e r s i t y h o s p i t a l s , number o f g e n e r a l p r a c t i t i o n e r s , number o f s p e c i a l i s t s p e r b e d , number o f n u r s i n g p e r s o n n e l per b e d , number o f n u r s i n g home beds , percentage c o v e r e d by compulsory i n s u r a n c e f o r low income f a m i l i e s , and index o f the p o p u l a t i o n d e n s i t y ) , and t h a t o t h e r sources o f c a r e ( e . g . , i n f a n t w e l f a r e c e n t e r s , s c h o o l p h y s i c i a n s ) s h o u l d p r o b a b l y be i n c l u d e d i n the a n a l y s i s . C o n n e l l e t a l . (1981) compared p o p u l a t i o n - b a s e d a d m i s s i o n r a t e s f o r M e d i c a i d c h i l d r e n i n 14 g e o g r a p h i c s u b d i v i s i o n s o f Washington S t a t e . The s t u d y p o p u l a t i o n c o n s i s t e d o f c h i l d r e n under 21 y e a r s o f age who were M e d i c a i d r e c i p i e n t s because of 53 low income and not because of s p e c i a l medical needs such as b l i n d n e s s , c h r o n i c d i s e a s e , or mental r e t a r d a t i o n . These c h i l d r e n made up approximately 7 percent of a l l c h i l d r e n under 21 years of age i n the S t a t e . The study showed dramatic d i f f e r e n c e s i n admission r a t e s among geographic s u b d i v i s i o n s . A r e g r e s s i o n a n a l y s i s of admission r a t e s a g a i n s t per c a p i t a h o s p i t a l bed supply and occupancy r a t e s showed no s i g n i f i c a n t c o r r e l a t i o n s . The c o r r e l a t i o n c o e f f i c i e n t f o r t o t a l m e d i c a l / s u r g i c a l admission r a t e s and bed supply was .28 and s u r g i c a l admission r a t e s and bed supply .25. Occupancy r a t e s were p o s i t i v e l y and s i g n i f i c a n t l y a s s o c i a t e d w i t h o v e r a l l s u r g i c a l and ENT admission r a t e s , i n d i c a t i n g t h a t areas w i t h f u l l r a t h e r than empty h o s p i t a l s had h i g h e r r a t e s of surgery. The study a l s o showed t h a t , except f o r s u r g i c a l h o s p i t a l i z a t i o n , admission r a t e s were not r e l a t e d t o the supply of p h y s i c i a n s . O v e r a l l , the study c o u l d not e x p l a i n w e l l the h i g h i n t e r - a r e a d i f f e r e n c e s i n p a e d i a t r i c h o s p i t a l use. The authors suggested as one p l a u s i b l e e x p l a n a t i o n t h a t the h i g h v a r i a t i o n i n admission r a t e s r e f l e c t s d i f f e r e n c e s i n community p r a c t i c e s t y l e s . Both two s t u d i e s (Van der Gaag e-h a 1 ., 1 975; and C o n n e l l eJ: a l . , 1981) used aggregate bed c a p a c i t y i n s t e a d of bed supply s p e c i f i c t o age group. H o s p i t a l beds i n a d u l t wards may not be s u b s t i t u t a b l e f o r p a e d i a t r i c beds and v i c e v e r s a . I f so, then one would expect c o e f f i c i e n t s on aggregate bed c a p a c i t y to be 5 4 downward b i a s e d . The b i a s would be l a r g e r i n the p a e d i a t r i c age group s i n c e the m a j o r i t y o f h o s p i t a l beds a re f o r a d u l t s . Wennberg and Kimm (1977) have a l s o p o i n t e d out the h i gh v a r i a b i l i t y of p a e d i a t r i c h o s p i t a l u se . They i d e n t i f i e d t w o f o l d d i f f e r e n c e s i n a g e - a d j u s t e d admi s s ion r a t e s among comparable h o s p i t a l s e r v i c e areas i n Vermont. When the da ta were a n a l y z e d by s p e c i f i c d i a gnose s , v a r i a t i o n s i n admi s s i on r a t e s by d i a g n o s i s were as g r e a t as s i x f o l d . A l though the au thor s d i d not s p e c i f i c a l l y s tudy the e f f e c t o f bed a v a i l a b i l i t y on h o s p i t a l u se , t hey showed t h a t d i f f e r e n c e s i n use of h o s p i t a l beds were a s s o c i a t e d w i t h v a r i a t i o n s i n p a e d i a t r i c p a t i e n t mix. In the lowest use a r e a s , most beds were devoted t o i n j u r i e s . The p r o p o r t i o n of beds devoted to i n f e c t i o u s d i s e a s e c o n d i t i o n s r o se marked ly w i t h i n c r e a s e d bed u se , i m p l y i n g l ower i n g t h r e s h o l d of admiss ions w i t h bed c a p a c i t y i n c r e a s e . The s tudy a l s o found t h a t the supp l y of surgeons was p o s i t i v e l y r e l a t e d t o the s u r g e r y r a t e . The au thor s suggested t h a t p h y s i c i a n s ' judgment i n d i a g n o s i s and p h y s i c i a n s ' b e l i e f i n the e f f e c t i v e n e s s of t rea tment a r e c r i t i c a l i n e x p l a i n i n g the v a r i a t i o n i n c h i l d r e n ' s h o s p i t a l u se . They a l s o commented on the d i f f i c u l t y i n p l a n n i n g the s i z e of h o s p i t a l c a p a c i t y : " When the m e d i c a l p r o f e s s i o n i t s e l f i s u n c e r t a i n about the p r o p e r , optimum use o f h o s p i t a l beds, then the s t a t e , as the c e r t i f i e r of need, i s i n a d i f f i c u l t p o s i t i o n . Requests f o r a d d i t i o n a l f a c i l i t i e s commonly come from areas t h a t a re a l r e a d y u s i n g h o s p i t a l s a t g r e a t e r than 5 5 the r a t e f o r the r e g i o n as a whole. I s s u i n g b u i l d i n g pe rmi t s t o such a reas w i l l i n c r e a s e the u t i l i z a t i o n d i f f e r e n t i a l between a r e a s . T h i s dilemma needs r e s o l u t i o n . " (Wennberg and Kimm, 1 9 7 7 , p. 3 9 0 ) . 2 . 6 . O ther f a c t o r s i n p a e d i a t r i c i n p a t i e n t use A l though ha rmfu l e f f e c t s of h o s p i t a l i z a t i o n on c h i l d r e n a re w e l l known t h e r e have been few e f f o r t s t o a s ses s the de te rm inan t s of p a e d i a t r i c h o s p i t a l i z a t i o n a t the p o p u l a t i o n l e v e l . P o l i c i e s t o c o n t r o l p a e d i a t r i c h o s p i t a l use seem t o have c o n c e n t r a t e d on p r o v i s i o n o f a l t e r n a t i v e modes o f c a r e (Harvard C h i l d H e a l t h P r o j e c t , 1 9 7 7 ) . On the o t h e r hand, t h e r e i s s t i l l a c o n c e r n , e s p e c i a l l y i n the U n i t e d S t a t e s , t h a t some subgroups of c h i l d r e n do not use h o s p i t a l s e r v i c e s as much as t hey shou ld because of f i n a n c i a l b a r r i e r s (Kozak and McCarthy, 1 9 8 4 ; Perrin et. a l . f 1 9 8 6 ) . The f a c t o r s t h a t a re r e l a t e d to c h i l d r e n ' s h e a l t h s t a t u s and h o s p i t a l use bear a s p e c i a l importance t o t h i s s tudy . Some of the demographic and soc ioeconomic c h a r a c t e r i s t i c s of the c h i l d p o p u l a t i o n can a c t as p roxy f o r a c t u a l h e a l t h s t a t u s i n the absence of b e t t e r measures. They may a l s o be p o t e n t i a l confounders i n s t u d y i n g the r e l a t i o n s h i p between day c a r e a v a i l a b i l i t y and i n p a t i e n t u t i l i z a t i o n . Roemer and Sha in ( 1 9 5 9 ) have emphasized the comp lex i t y of the f a c t o r s a f f e c t i n g h o s p i t a l u t i l i z a t i o n . Whi le s e v e r a l f a c t o r s opera te 56 d i r e c t l y and i n d e p e n d e n t l y t o i n f l u e n c e h o s p i t a l u se , the prob lem i s made more d i f f i c u l t by the f a c t t h a t they a l s o i n f l u e n c e each o t h e r . Both demographic and soc ioeconomic c h a r a c t e r i s t i c s o f a p o p u l a t i o n can have an impact on the i l l n e s s l e v e l of t h a t p o p u l a t i o n , but they can a l s o i n t e r a c t i n the p roce s se s t h a t l e a d to h o s p i t a l u se . 2 . 6 . 1 . P r e v a l e n c e , i n c i d e n c e and t ype o f i l l n e s s I n c i d e n c e , p r e v a l e n c e and type of i l l n e s s i n the p o p u l a t i o n form the f o u n d a t i o n f o r h o s p i t a l u t i l i z a t i o n . A l though t h i s f a c t o r has sometimes been c o n s i d e r e d a lmost the o n l y de te rm inan t of h o s p i t a l i z a t i o n e x p e r i e n c e , da ta on the i n c i d e n c e and p r e v a l e n c e of d i s e a s e w i l l t e l l us v e r y l i t t l e about h o s p i t a l i z a t i o n demand, u n l e s s we combine them w i t h o t h e r i n f o r m a t i o n o r the a t t i t u d e s of c h i l d r e n o r t h e i r pa ren t s and the p o l i c i e s and p r a c t i c e s of h o s p i t a l s and p h y s i c i a n s i n the community. Even w i t h a c l e a r l y d e f i n a b l e d i s e a s e the c h i l d , the pa rent s and the p h y s i c i a n may have d i f f e r e n t p e r c e p t i o n s of the need f o r o r t i m i n g of h o s p i t a l i z a t i o n . Fur thermore , the d e f i n i t i o n of i l l n e s s depends on p r e v a i l i n g concepts of n o r m a l i t y . With r i s i n g s tandards of l i v i n g and more r e f i n e d s c i e n t i f i c t e c h n i q u e s more and more c o n d i t i o n s a re i n c l u d e d i n the domain o f m e d i c i n e and l a b e l e d as i l l n e s s ( Z o l a , 1975). H igh i n t r a - a n d i n t e r - o b s e r v e r v a r i a t i o n i n d i a g n o s i n g d i s e a s e s makes t h i s f a c t o r even more complex. 57 A s tudy on need f o r t o n s i l l e c t o m y i s a c l a s s i c example of how vague the i n f l u e n c e of d i s e a s e can be on h o s p i t a l u t i l i z a t i o n (Denzer and F e l s h i n , 1943; Bakwin, 1945). In t h i s s tudy 1,000 e l e v e n - y e a r - o l d s c h o o l c h i l d r e n were surveyed i n New York. 61 p e r c e n t were found to have had t h e i r t o n s i l s removed. The rema in ing 389 c h i l d r e n were then examined i n r e l a y s by twenty s c h o o l p h y s i c i a n s . On the f i r s t exam ina t i on , 174 (45 p e r c e n t ) of these h e a l t h y c h i l d r e n were recommended f o r t o n s i l l e c t o m y . Out of 215 c h i l d r e n c o n s i d e r e d as h e a l t h y i n t h i s f i r s t examina t i on , another 95 (44 p e r c e n t ) were s e l e c t e d f o r t o n s i l l e c t o m y when another team of p h y s i c i a n s was put t o work. When the rema in ing 119 c h i l d r e n t h a t had been c o n s i d e r e d as h e a l t h y i n the two examinat ions were sent t o a t h i r d group of p h y s i c i a n s , 53 (46 p e r c e n t ) were recommended f o r t o n s i l l e c t o m y . One of the c o n c l u s i o n s of the s tudy was t h a t the chance of a c h i l d ' s b e i n g recommended f o r o p e r a t i o n depended p r i n c i p a l l y on the p h y s i c i a n r a t h e r than on the c h i l d ' s h e a l t h . In 1978, the h i g h e s t d i s c h a r g e r a t e f o r Canadian c h i l d r e n under 15 yea r s of age was f o r the c a t e g o r y " d i s e a s e s of the r e s p i r a t o r y s y s tem" , a c c o u n t i n g f o r 38 p e r c e n t of a l l d i s c h a r g e s (Kozak and McCarthy, 1984). The Canadian d i s c h a r g e r a t e f o r c h i l d r e n w i t h r e s p i r a t o r y d i s e a s e s was 71 p e r c e n t h i g h e r than the U.S. r a t e . The l a r g e d i f f e r e n c e i s not l i k e l y caused by a d i f f e r e n c e i n the i n c i d e n c e o r d u r a t i o n of r e s p i r a t o r y d i s e a s e s between the two c o u n t r i e s ; f a c t o r s o t h e r 5 8 than d i s e a s e i t s e l f determine h o s p i t a l use as w e l l . The second h i g h e s t d i s c h a r g e r a t e f o r c h i l d r e n was a c c i d e n t s , p o i s o n i n g , and v i o l e n c e , and the t h i r d h i g h e s t c a t e g o r y was i n f e c t i v e and p a r a s i t i c d i s e a s e s (Kozak and McCarthy, 1984). These t h r e e c a t e g o r i e s accounted f o r 60 p e r c e n t of a l l d i s c h a r g e s i n c h i l d r e n i n Canada. Sheps (1980) r e p o r t e d v e r y s i m i l a r r e s u l t s i n B r i t i s h Co lumbia . R e s p i r a t o r y d i s e a s e s , f o l l o w e d by a c c i d e n t s , p o i s o n i n g , and v i o l e n c e ; i n f e c t i v e and p a r a s i t i c d i s e a s e s ; d i s e a s e s of the nervous and d i g e s t i v e sys tem; and c o n g e n i t a l anomal ies were the most common d i a g n o s t i c groups and accounted f o r over 75 p e r c e n t o f adm i s s i on s . The f i r s t t h r e e d i a g n o s t i c groups accounted f o r 62 p e r c e n t of a l l c a se s . Of the i n d i v i d u a l d i a g n o s t i c c a t e g o r i e s , hyper t rophy of t o n s i l s and adenoids had the h i g h e s t d i s c h a r g e r a t e i n Canada i n 1978 (Kozak and McCarthy, 1984). Changes i n . inc idence of d i s e a s e i n c h i l d r e n can c o n t r i b u t e t o changes of p a e d i a t r i c h o s p i t a l use over t i m e . The impact of the d e c l i n e i n i n c i d e n c e of i n f e c t i o u s d i s e a s e s i n c h i l d r e n ( e . g . t u b e r c u l o s i s and p o l i o ) on h o s p i t a l u t i l i z a t i o n r a t e s i s g e n e r a l l y known. However, w i t h improv ing h e a l t h s t a t u s of c h i l d r e n , the r e l a t i v e importance of d i s e a s e as a de terminant of h o s p i t a l u t i l i z a t i o n r a t e s may d e c r e a s e , as o t h e r f a c t o r s become more and more impor tant i f h o s p i t a l bed supp l y does not a d j u s t . 5 9 Because f a c t o r s o t h e r than d i s e a s e i t s e l f p l a y a p a r t i n d e t e r m i n i n g h o s p i t a l u se , h o s p i t a l u t i l i z a t i o n da ta may not be v e r y r e l i a b l e f o r i n f e r r i n g t r u e i n c i d e n c e and p r e v a l e n c e , o r i n o t h e r words, h o s p i t a l c a re needs , i n a p o p u l a t i o n . P r e v a l e n c e o r i n c i d e n c e (depending on the t ype of d i s e a s e ) may be a major de terminant of h o s p i t a l u t i l i z a t i o n i n a p o p u l a t i o n , but f o r most d i s e a s e s t h e r e a re no measures a v a i l a b l e , independent of u t i l i z a t i o n . 2 .6 .2 . Demographic f a c t o r s Of the d i f f e r e n t demographic f a c t o r s , age and sex have c l e a r l y shown the h i g h e s t a s s o c i a t i o n w i th the r a t e of p a e d i a t r i c h o s p i t a l u se . Data on the r e l a t i o n s h i p between age and h o s p i t a l use i n c h i l d r e n shows t h a t i n f a n t s under 1 yea r o f age ( e x c l u d i n g newborns) have a lmost a f i v e t imes h i g h e r d i s c h a r g e r a t e and over 5.5 t imes h i g h e r number of h o s p i t a l days than 10-14 y e a r o l d c h i l d r e n (Kozak and McCarthy, 1984). H o s p i t a l u t i l i z a t i o n r a t e s of c h i l d r e n l e s s than one y e a r of age equa l those of 65-74 y e a r o l d s . Boys use h o s p i t a l s e r v i c e s more o f t e n than g i r l s (about 26 p e r c e n t more d i s c h a r g e s ) . (Kozak and McCarthy, 1984). Race has been shown t o be r e l a t e d t o m o r t a l i t y and h e a l t h s t a t u s of c h i l d r e n . B l ack c h i l d r e n have s u b s t a n t i a l l y h i g h e r m o r t a l i t y r a t e s than w h i t e s . However, the r a c i a l d i f f e r e n c e s seem t o d i s a p p e a r i n the h i g h e s t income groups , except among 60 neonates (Mare, 1982). C o l l e and Grossman (1978) found t h a t b l a c k c h i l d r e n make more v i s i t s t o p h y s i c i a n s than wh i te c h i l d r e n even when the e f f e c t o f - f a m i l y income, i n s u r a n c e coverage , mo the r ' s s c h o o l i n g , and p h y s i c i a n a v a i l a b i l i t y have been c o n t r o l l e d . B l ack c h i l d r e n were a l s o much more l i k e l y to have v i s i t s a t " p u b l i c s i t e s " ( h o s p i t a l emergency rooms, h o s p i t a l o u t p a t i e n t depar tments , and p u b l i c c l i n i c s not connected w i t h h o s p i t a l s ) than i n p h y s i c i a n s ' o f f i c e s . In B .C . , c h i l d r e n o f N a t i v e Ind ians a re h o s p i t a l i z e d about t h r e e t o f o u r t imes more f r e q u e n t l y than n o n - i n d i a n c h i l d r e n and f o r l o n g e r p e r i o d s than o the r s (Robinson and Evans, 1973). In a d d i t i o n to r a c e , e t h n i c compos i t i on and m i g r a t i o n s t a t u s o f a p o p u l a t i o n have been r e l a t e d t o h e a l t h s t a t u s and h o s p i t a l u t i l i z a t i o n a t the t o t a l p o p u l a t i o n l e v e l (Anderson, 1973). U r b a n - r u r a l d i f f e r e n t i a l s i n h o s p i t a l u t i l i z a t i o n have been known f o r a l ong t ime (Roemer and S h a i n , 1959). In g e n e r a l , h o s p i t a l admi s s i on r a t e s a re h i g h e r and average l e n g t h of s t a y i s l o n g e r i n r u r a l a reas compared t o urban a reas (Anderson, 1973). C o n n e l l ' s e t a l . (1981) s tudy i n Washington S t a t e found n e a r l y i d e n t i c a l t o t a l admis s ion r a t e s f o r urban and r u r a l a reas f o r M e d i c a i d c h i l d r e n under 21 year s of age. However, s u r g i c a l admis s ions were s i g n i f i c a n t l y h i g h e r and m e d i c a l admi s s ions were s i g n i f i c a n t l y lower i n urban a r e a s . Bombardier e t a l . (1977) found s i m i l a r u r b a n - r u r a l d i f f e r e n c e s f o r s u r g i c a l u t i l i z a t i o n , but when u t i l i z a t i o n r a t e s were a d j u s t e d f o r income the d i f f e r e n t i a l became n o n s i g n i f i c a n t . Long (1981) 61 has r e p o r t e d ev idence to support the h y p o t h e s i s t h a t r e s i d e n t i a l l o c a t i o n serves as a p roxy f o r m a r i t a l and f a m i l y r e l a t i o n s h i p , o c c u p a t i o n , and h e a l t h s t a t u s . 2 .6 .3 . Soc ioeconomic f a c t o r s S o c i a l and economic f a c t o r s a r e impor tant de te rminant s of both c h i l d r e n ' s h e a l t h s t a t u s and t h e i r h e a l t h s e r v i c e s use . C l i n i c a l and e p i d e m i o l o g i c s t u d i e s i n d i c a t e a h i g h e r f requency of h e a l t h problems among poor c h i l d r e n ( S t a r f i e l d , 1982^ Egbuoner and S t a r f i e l d , 1982; Dut ton , 1985). A l s o , t h e i r h e a l t h problems tend to be more severe than those of non-poor c h i l d r e n . H o s p i t a l i z a t i o n r a t e s a re h i g h e r among poor c h i l d r e n than nonpoor c h i l d r e n . In a d d i t i o n , the average number of days spent i n the h o s p i t a l i s g r e a t e r among c h i l d r e n from low income f a m i l i e s than among o t h e r c h i l d r e n ( S t a r f i e l d , 1982). On the o t h e r hand, a p o s i t i v e r e l a t i o n s h i p between s u r g i c a l u t i l i z a t i o n and f a m i l y income has been found t o be s t r o n g e s t f o r c h i l d r e n (Bombardier e t a l . f 1977). O c c u p a t i o n a l c l a s s of f a t h e r and mother ' s s c h o o l i n g , as i n d i c a t o r s of f a m i l y s o c i a l s t a t u s , have been a l s o r e l a t e d to c h i l d r e n ' s h e a l t h (Mare, 1982). The lower the f a t h e r ' s o c c u p a t i o n a l c l a s s the h i g h e r the m o r t a l i t y of c h i l d r e n aged 1-14. T h i s e f f e c t seems t o be s t r o n g e s t f o r deaths from a c c i d e n t s , p o i s o n i n g and v i o l e n c e . Independent p o s i t i v e e f f e c t s of mother ' s s c h o o l i n g on both c h i l d r e n ' s h e a l t h s t a t u s 62 (Mare, 1982) and use of ambulatory p e a d i a t r i c s e r v i c e s ( C o l l e and Grossman, 1978) have been r e p o r t e d . E d u c a t i o n a l l e v e l i n a p o p u l a t i o n has been found to be n e g a t i v e l y a s s o c i a t e d w i t h s u r g i c a l u t i l i z a t i o n (Bombardier e t a 1.. 1977) Unemployment has had v e r y l i t t l e d i r e c t impact on h o s p i t a l u t i l i z a t i o n i n t o t a l p o p u l a t i o n s (Anderson, 1973), but the s i t u a t i o n may be d i f f e r e n t w i t h i n a p a e d i a t r i c p o p u l a t i o n . C h i l d r e n l i v i n g i n d e p r i v e d d i s t r i c t s i n Glasgow were on average about n i n e t imes more l i k e l y t o be admi t ted t o h o s p i t a l f o r any reason than c h i l d r e n i n n o n - d e p r i v e d d i s t r i c t s (Maclure and S tewart , 1984). The d e p r i v a t i o n v a r i a b l e s most s t r o n g l y c o r r e l a t e d w i t h admis s ion r a t e s were overc rowd ing i n households and p a r e n t a l unemployment. T h i s l i t e r a t u r e rev iew p o i n t s out t h a t both demographic and soc ioeconomic f a c t o r s have an i n f l u e n c e on p a e d i a t r i c h o s p i t a l u t i l i z a t i o n . E f f e c t s seem t o be complex and, i n many c a s e s , not y e t c o m p l e t e l y under s tood . Some of the f a c t o r s , such as age, sex, r a c e , and f a m i l y income, a re c l o s e l y r e l a t e d to c h i l d r e n ' s h e a l t h s t a t u s and p r o b a b l y r e f l e c t some degree of h o s p i t a l c a re need. A l though a s s o c i a t i o n s between p a e d i a t r i c i n p a t i e n t use and v a r i o u s demographic and soc ioeconomic f a c t o r s i n a p o p u l a t i o n a re impor tant i n under s t and ing the c o m p l e x i t y of p a e d i a t r i c h o s p i t a l u t i l i z a t i o n , the se a s s o c i a t i o n s a re not the main focus of t h i s s tudy . However, e f f e c t s of demographic and soc ioeconomic f a c t o r s shou ld be 6 3 h e l d con s t an t i n o r d e r to s epa ra te out the net e f f e c t , i f any, of day c a r e su r ge ry on p a e d i a t r i c i n p a t i e n t u t i l i z a t i o n . For example, i n t r o d u c t i o n of day c a r e su r ge ry may c o i n c i d e s imu l taneous changes i n demographic and soc ioeconomic c h a r a c t e r i s t i c s of the p a e d i a t r i c p o p u l a t i o n , wh i ch , i f not c o n t r o l l e d f o r , c o u l d l e a d to b i a s e d e s t ima te s of the a s s o c i a t i o n between day ca re su r ge ry and p a e d i a t r i c i n p a t i e n t u se . 2 .6 .4 . M e d i c a l c a r e a v a i l a b i l i t y Be fo re r e v i e w i n g a s s o c i a t i o n s between m e d i c a l c a r e o r p h y s i c i a n a v a i l a b i l i t y and i n p a t i e n t u t i l i z a t i o n , a c l o s e r look a t the u n d e r l y i n g t h e o r i e s i s u s e f u l l s i n c e h e a l t h ca re d i f f e r s i n s e v e r a l ways from the s tandard "commodity" of the economic t e x t b o o k s . Asymmetry of i n f o r m a t i o n between u se r and p r o v i d e r of h e a l t h c a re i s p r o b a b l y i t s most fundamenta l p e c u l i a r i t y as a commodity, and the source o f the most s e r i o u s f a i l u r e s o f market p roces se s as r e s o u r c e a l l o c a t o r s i n t h i s f i e l d (Evans, 1984). Asymmetry o f i n f o r m a t i o n stems from the n o t i o n t h a t i t i s h e a l t h , as a s t a t u s , r a t h e r than h e a l t h c a r e , as a commodity, which i s of v a l u e t o i t s u s e r s . But h e a l t h cannot be bought d i r e c t l y , o n l y s e r v i c e s ( p r e v e n t i v e o r c u r a t i v e , ambulatory o r h o s p i t a l ) can . A l though the consumer of h e a l t h s e r v i c e s has s o v e r e i g n i t y i n knowing the v a l u e and u t i l i t y of a h e a l t h s t a t u s t o h i m s e l f , i t i s the expe r t p r o v i d e r who i s much b e t t e r in formed about the c o n t r i b u t i o n of 64 h e a l t h s e r v i c e s t o the ' p r o d u c t i o n ' of h e a l t h (Evans, 1984). Thus, the consumer i s no l onge r the bes t judge of h i s i n t e r e s t s , but must r e l y on the p r o v i d e r ' s a d v i c e , which i n t u r n i m p l i e s t h a t the p r o v i d e r a ccep t s some r e s p o n s i b i l i t y f o r s e r v i n g the consumer ' s i n t e r e s t . But the p r o v i d e r cannot , a t the same t i m e , be a p e r f e c t agent , s e r v i n g the i n t e r e s t of the c o n s u m e r / p a t i e n t , and an economic p r i n c i p a l who has i n t e r e s t s of h i s own. H i s economic, p r o f e s s i o n a l , and p e r s o n a l i n t e r e s t s a r e p a r t i a l l y congruent and p a r t l y i n c o n f l i c t w i t h those of the c o n s u m e r / p a t i e n t . In t h i s i ncomp le te agency framework the d i r e c t i n f l u e n c e by the p r o v i d e r on the c o n s u m e r / p a t i e n t ' s p e r c e p t i o n s of both h e a l t h s t a t u s and h e a l t h c a r e e f f i c a c y depends on the p r o v i d e r ' s c i r c u m s t a n c e s : economic, p r o f e s s i o n a l , and p e r s o n a l (Evans, 1984). Demand curve f o r h e a l t h c a re s e r v i c e s i s s h i f t e d by the a d v i c e p r o v i d e r s g i v e . T h i s d i r e c t i n f l u e n c e over demand i s sometimes r e f e r r e d to as K i i p p l i p r - i n r i n r p H riemanrf . Roemer 's Law i s a r e f l e c t i o n of s u p p l i e r - i n d u c e d demand i n the h o s p i t a l s e c t o r . I t can app l y t o p h y s i c i a n s supp l y as w e l l ; more c a p a c i t y l eads to more use ( S toddar t and B a r e r , 1981; Evans, 1984). In a d d i t i o n t o o v e r a l l l e v e l s of m e d i c a l c a r e a c t i v i t y , s u r g i c a l u t i l i z a t i o n r a t e s have a l s o been found t o v a r y w i t h supp l y o f p h y s i c i a n s and, i n p a r t i c u l a r l y , surgeons (Vayda and Ader son , 1975; Vayda e t a l . , 1976; Fuchs , 1978; Roos, 1983). F i n d i n g s have been s i m i l a r i n the p a e d i a t r i c age group (Wennberg and Kimm, 1977; C o n n e l l e t a l . , 65 1981). U t i l i z a t i o n s t u d i e s have not i n d i c a t e d a c o n s i s t e n t r e l a t i o n from the overa11 p h y s i c i a n s tock t o t o t a l h o s p i t a l u se ; r a t h e r they have emphasized the i n f l u e n c e of i n d i v i d u a l p r a c t i t i o n e r s and t h e i r p e r c e p t i o n s and p r e f e r e n c e s (Roos e_t a 1 . r 1986). There a re some i n d i c a t i o n s t h a t the number of p a e d i a t r i c i a n s per c a p i t a has a n e g a t i v e e f f e c t on c h i l d r e n ' s h o s p i t a l u t i l i z a t i o n r a t e s (Osgood e t a 1 . r 1980; Kozak and McCarthy, 1984). P h y s i c i a n s ' b e h a v i o r i n response t o exogenous i n c r e a s e i n supp l y may r e f l e c t economic, p r o f e s s i o n a l , o r p e r s o n a l i n t e r e s t s . In g e n e r a l , when average workloads and incomes f a l l , due t o exogenous i n c r e a s e s i n s upp l y , p h y s i c i a n s change t h e i r p r a c t i c e p a t t e r n s t o i n c r e a s e u t i l i z a t i o n . T h i s c o u l d be i n t e r p r e t e d as the r e s u l t of p h y s i c i a n s a d j u s t i n g t h e i r b e h a v i o r t o seek some s o r t of " t a r g e t " income. But i f the expans ion i s i n s u f f i c i e n t t o m a i n t a i n income " t a r g e t s " , p r i c e s w i l l be i n c r e a s e d as w e l l . T h i s would e x p l a i n the p o s i t i v e c o r r e l a t i o n u s u a l l y found between a v a i l a b l e supp l y of p h y s i c i a n s and p r i c e (Evans, 1984). W i ldavsky (1977) argues t h a t med i c ine i s o n l y p a r t i a l l y and i m p e r f e c t l y r e l a t e d to h e a l t h and , t h u s , p h y s i c i a n s themselves a re o f t e n u n c e r t a i n as t o e f f i c a c y of c a r e . T h i s u n c e r t a i n t y i s s o l v e d by do ing more: t h e r e i s always one more t h i n g t h a t might be done -ano ther c o n s u l t a t i o n , a new d rug , a d i f f e r e n t t r e a t m e n t . T h i s i s c l o s e l y r e l a t e d t o an e t h i c of ' d o i n g e v e r y t h i n g p o s s i b l e ' f o r p a t i e n t s , s u b j e c t t o c o n s t r a i n t s on t ime and energy , so 66 t h a t when a p h y s i c i a n sees fewer p a t i e n t s (because o f r i s e i n p h y s i c i a n - t o - p o p u l a t i o n r a t i o , e . g . ) , he f e e l s a b l e t o do more f o r each . Whether the mot ives of p h y s i c i a n s a r e t o i n c r e a s e comprehens iveness o f c a r e , o r incomes, mat ter s l i t t l e t o the outcome. P r o f e s s i o n a l e t h i c s and p r a c t i t i o n e r s ' concepts of " p r a c t i c e s t y l e " (views on how med ic ine ought to be p r a c t i c e ) can bound and r e g u l a t e the demand-generat ion p r o c e s s . The p r o v i d e r ' s o b j e c t i v e s i n c l u d e economic as w e l l as non-economic components. There c o u l d be a t r a d e o f f between d o l l a r s and p r o f e s s i o n a l p r i d e . I f income and work load s h r i n k (due t o i n c r e a s e i n p h y s i c i a n - t o - p o p u l a t i o n r a t i o , e . g . ) , the p r a c t i t i o n e r c o u l d change the c r i t e r i a which governs h i s recommendations t o p a t i e n t s , and genera te more demand. The c o n s i s t e n t response of u t i l i z a t i o n to numbers of p r a c t i t i o n e r s , r e g a r d l e s s of p r i c e l e v e l s , a l l over Nor th A m e r i c a , i s i n d i c a t i v e of t h i s t r a d e - o f f i n a c t i o n (Evans, 1984). S tandards of p r a c t i c e adapt over t ime i n response to c u r r e n t p r a c t i c e , one ' s own and o t h e r s . Thus a s h i f t t o recommending more s e r v i c i n g , which may i n i t i a l l y be a response t o economic f a c t o r s , becomes over t ime the new s t a n d a r d . S tandards and p r a c t i c e p a t t e r n s can a l s o change because of g e n e r a l s h i f t s i n t r a i n i n g o r m e d i c a l i n f o r m a t i o n ( e . g . , i n the case of t o n s i l l e c t o m i e s ) ( K i m m , 1977), o r f o r more l o c a l reasons (Wennberg and G i t t e l s o h n , 1982; Roos, 1983). 67 P h y s i c i a n a v a i l a b i l i t y i s a p o t e n t i a l con found ing f a c t o r i n s t u d y i n g the r e l a t i o n s h i p between day ca re s u r g e r y and i n p a t i e n t u t i l i z a t i o n and, t h e r e f o r e , shou ld be c o n t r o l l e d f o r . I t i s p o s s i b l e t h a t h i gh l e v e l of p h y s i c i a n a v a i l a b i l i t y l eads t o both h i gh l e v e l s of p a e d i a t r i c i n p a t i e n t a c t i v i t y , and ( f o r g i v e n bed s tock ) i n c r e a s e d p r e s s u r e f o r day ca re s u r g e r y use . T h i s c o u l d mask a net n e g a t i v e e f f e c t from day ca re s u r g e r y to i n p a t i e n t use . On the o t h e r hand, one can h y p o t h e s i z e t h a t some s p e c i a l i s t groups ( e . g . , g e n e r a l and f a m i l y p r a c t i t i o n e r s , and p a e d i a t r i c i a n s ) both s u b s t i t u t e f o r p a e d i a t r i c i n p a t i e n t c a re and i n c r e a s e p r e s s u r e f o r day ca re s u r g e r y ( f o r q u a l i t y rea sons , e . g . ) . H igh supp l y of these s p e c i a l i s t s r e l a t i v e t o o t h e r s p e c i a l i s t s may mask a net g e n e r a t i o n e f f e c t of day ca re su r ge ry . A l a r g e and a c t i v e p h y s i c i a n p o p u l a t i o n can l e a d t o p r e s s u r e f o r more bed a v a i l a b i l i t y . Bed supp l y has been shown t o c o r r e l a t e w i t h p h y s i c i a n supp l y (Roos, 1983). A p o s i t i v e i n f l u e n c e o f p h y s i c i a n s tock on both beds and i n p a t i e n t use c o u l d l e a d to an i n a p p r o p r i a t e i n f e r e n c e t h a t bed c a p a c i t y a l one determines i n p a t i e n t use . T h i s l i t e r a t u r e rev iew emphasizes a l s o the need f o r c o n t r o l l i n g e f f e c t s of d i f f e r e n c e s i n p r a c t i c e p a t t e r n s and s tandards ( i . e . , m e d i c a l ' c u l t u r e ' ) a c ro s s a reas and over t ime . Change, f o r example, i n h o s p i t a l i z a t i o n p a t t e r n s , due to economic o r o t h e r rea sons , i n one a re but not i n o t h e r s can 6 8 cause b i a s i n c r o s s - a r e a s t u d i e s . Change i n recommending the o p e r a t i o n of t o n s i l l e c t o m y has been a major s h i f t i n m e d i c a l ' c u l t u r e ' i n r e s p e c t t o p a e d i a t r i c i n p a t i e n t s u r g e r y i n the 1970s (Evans and Rob inson, 1980). I f i t i s not accounted f o r i n a t i m e - s e r i e s " s t u d y , i t c o u l d l e a d to a f a l s e i n t e r p r e t a t i o n t h a t i n c r e a s e i n day ca re s u r g e r y i n the 1970s has s u b s t i t u t e d f o r p a e d i a t r i c i n p a t i e n t s u r g e r y . 2 .7. Summary o f l i t e r a t u r e r ev i ew Day c a r e s u r g e r y , e s p e c i a l l y i n the p a e d i a t r i c age group, has c l e a r q u a l i t y based advantages over the c o n v e n t i o n a l i n p a t i e n t s u r g e r y . Both r i s k of h o s p i t a l - a c q u i r e d i n f e c t i o n s and of u n d e s i r a b l e p s y c h o s o c i a l e f f e c t s on c h i l d r e n can be m in im ized w i thou t compromising the q u a l i t y o f o p e r a t i o n s . F e a s i b i l i t y and s a f e t y of p a e d i a t r i c day c a r e s u r g e r y has been demonstrated w i t h s e v e r a l s p e c i a l t i e s . D e t a i l e d c o s t ana l y se s have shown t h a t ep i sode of c a re i n day ca re s u r g e r y i s 50 - 70 p e r c e n t l e s s expens i ve than s i m i l a r t rea tment on the i n p a t i e n t wards. However, t h e r e i s no c l e a r ev i dence t h a t lower u n i t c o s t s of day c a r e su r ge ry w i l l be t r a n s l a t e d i n t o sav ings i n t o t a l h e a l t h c a re e x p e n d i t u r e s . T h i s would r e q u i r e t h a t day c a r e s u r g e r y s u b s t i t u t e s f o r more expens i ve i n p a t i e n t c a re and t h a t beds f r e e d by s u b s t i t u t i o n would not be f i l l e d by o t h e r s . Response o f use o f i n p a t i e n t c a r e t o day c a r e s u r g e r y , o t h e r t h i n g s b e i n g e q u a l , i s of utmost importance i n making f i n a l 69 c o n c l u s i o n s on the economic advantages of day ca re su r ge ry i n a p a e d i a t r i c p o p u l a t i o n . There a re s e v e r a l confound ing f a c t o r s t h a t may d i s t o r t the o b s e r v a t i o n s of the r e l a t i o n s h i p between day c a r e s u r g e r y and i n p a t i e n t u se . E f f e c t s o f these f a c t o r s shou ld be c o n t r o l l e d f o r , b e f o r e making any f i n a l c o n c l u s i o n s on the r e l a t i o n s h i p . P a e d i a t r i c bed supp l y i s a p o t e n t i a l confounder i n s t u d y i n g day c a r e s u r g e r y e f f e c t ( i f any) on i n p a t i e n t u t i l i z a t i o n . Roemer 's Law suggests t h a t bed c a p a c i t y a v a i l a b l e determines the l e v e l o f h o s p i t a l u t i l i z a t i o n i n a p o p u l a t i o n . A l t h o u g h , t h e r e i s a l a c k of c l e a r ev idence t h a t Roemer's Law i s working i n a p a e d i a t r i c p o p u l a t i o n , i t s e x i s t e n c e shou ld be s t u d i e d when r e v e a l i n g a s s o c i a t i o n s between p a e d i a t r i c day ca re s u r g e r y and i n p a t i e n t u se . P a e d i a t r i c day c a r e s u r g e r y c o u l d have been i n t r o d u c e d i n an a rea because t h e r e i s o n l y few i n p a t i e n t beds a v a i l a b l e . I f bed supp l y c r e a t e s i n p a t i e n t u t i l i z a t i o n , l a c k of adjustment f o r t h i s e f f e c t can l e a d to p o t e n t i a l f a l s e i n t e r p r e t a t i o n t h a t day ca re s u r g e r y s u b s t i t u t e s f o r i n p a t i e n t u t i l i z a t i o n . S e v e r a l demographic and soc ioeconomic f a c t o r s have complex e f f e c t s on and a s s o c i a t i o n s w i t h p a e d i a t r i c i n p a t i e n t u t i l i z a t i o n . In o r d e r to r e v e a l the r e l a t i o n s h i p between day c a r e s u r g e r y and i n p a t i e n t u se , other t h i n g s being equal r e f f e c t s of t he se f a c t o r s shou ld be c o n t r o l l e d f o r . Some of the 70 demographic and soc ioeconomic c h a r a c t e r i s t i c s o f the p a e d i a t r i c p o p u l a t i o n a re a s s o c i a t e d w i t h the h e a l t h s t a t u s of t h a t p o p u l a t i o n . A l t h o u g h , h e a l t h s t a t u s determines h o s p i t a l c a re needs and the reby h o s p i t a l u t i l i z a t i o n , t h e r e a r e v e r y few measures a v a i l a b l e of these needs independent of u t i l i z a t i o n . P h y s i c i a n supp l y and s h i f t s i n med i ca l ' c u l t u r e ' a c r o s s r e g i o n s and over t ime a re a l s o impor tant p o t e n t i a l confounders i n s t u d y i n g the r e l a t i o n s h i p between p a e d i a t r i c day c a r e s u r g e r y and i n p a t i e n t u se . However, p h y s i c i a n s ' p r a c t i c e p a t t e r n s cannot be measured by a 'head c o u n t ' o f p h y s i c i a n s . The adjustment would need a c o n t r o l f o r t i m e - and a r e a -s p e c i f i c e f f e c t s . 71 3 . DATA SOURCES AND METHODS 3 .1. S tudy u n i t and r e s e a r c h d e s i g n The p r i n c i p a l i n t e r e s t i n t h i s s tudy i s i n the r e l a t i o n s h i p between day c a r e s u r g e r y a v a i l a b i l i t y and p a e d i a t r i c i n p a t i e n t u t i l i z a t i o n . The main h y p o t h e s i z e d con found ing f a c t o r i s the bed c a p a c i t y a v a i l a b l e t o the p a e d i a t r i c p o p u l a t i o n . A c c o r d i n g t o a " s u p p l y " model , h o s p i t a l c a p a c i t y ( i n p a t i e n t and day ca re ) genera tes i t s own demand. Day ca re s u r g e r y c o u l d d i r e c t l y genera te i t s own demand (no s u b s t i t u t i o n f o r i n p a t i e n t ca re ) o r , i f some s u b s t i t u t i o n o c c u r r e s , g e n e r a t i o n c o u l d t ake p l a c e by f i l l - i n of f r e e d beds by o t h e r p a t i e n t s . In a d d i t i o n t o c o n t r o l l i n g f o r p o t e n t i a l bed s u p p l y e f f e c t i n s t u d y i n g the r e l a t i o n s h i p between day c a r e s u r g e r y and i n p a t i e n t u se , i n c l u s i o n of a bed c a p a c i t y measure i n the s tudy makes i t p o s s i b l e t o examine t h a t p o t e n t i a l e f f e c t i t s e l f ( i . e . , e x i s t e n c e of Roemer's Law i n a p a e d i a t r i c p o p u l a t i o n ) . Due t o the na tu re of the u n d e r l y i n g prob lem, the l o g i c a l s tudy u n i t i s an aggregate of p e o p l e , a p o p u l a t i o n . A h o s p i t a l based approach c o u l d not answer the s tudy q u e s t i o n s , because day ca re su r ge ry a v a i l a b i l i t y i n one h o s p i t a l may draw p a t i e n t s from o t h e r i n s t i t u t i o n s . The o v e r a l l s u b s t i t u t i o n / g e n e r a t i o n e f f e c t i s o n l y o b s e r v a b l e a t a r e g i o n a l , p o p u l a t i o n l e v e l . Fo r t h i s reason the " s c h o o l d i s t r i c t " was s e l e c t e d as the u n i t of o b s e r v a t i o n i n t h i s 72 s tudy . By u s i n g s m a l l a reas l i k e s c h o o l d i s t r i c t s , a g r e a t e r homogeneity i s a c h i e v e d f o r each u n i t as w e l l as a g r e a t e r number of u n i t s . Fo r t h i s reason s c h o o l d i s t r i c t s a r e more d e s i r a b l e than l a r g e r a r e a s , l i k e h e a l t h r e g i o n s o r r e g i o n a l h o s p i t a l d i s t r i c t s , when examining c o r r e l a t e s o f u t i l i z a t i o n ( J o f f e , 1979). There were b a s i c a l l y t h r e e d i f f e r e n t r e s e a r c h de s i gn s t h a t c o u l d have been employed i n t h i s s tudy . The most commonly used r e s e a r c h d e s i g n i n h o s p i t a l u t i l i z a t i o n s t u d i e s has been a compar i son of s e v e r a l a reas o r p o p u l a t i o n s a t one p o i n t i n t ime ( c r o s s - s e c t i o n a l ) . A l though one can a d j u s t f o r the e f f e c t s of a r e a - s p e c i f i c confound ing f a c t o r s w i t h t h i s d e s i g n , the i n t e r p r e t a t i o n of c o r r e l a t i o n s as c a u s a l i s hazardous w i thou t knowing the t ime-dependent e f f e c t s . Another r e s e a r c h d e s i g n , a t ime s e r i e s a n a l y s i s of a p o p u l a t i o n , u s u a l l y l a c k s s u f f i c i e n t da ta p o i n t s t o p r o v i d e the degrees of s t a t i s t i c a l freedom n e c e s s a r y t o d i s e n t a n g l e the m u l t i t u d e of f o r c e s which might s i m u l t a n e o u s l y a f f e c t p a e d i a t r i c i n p a t i e n t u se . However, one c o u l d a d j u s t f o r the e f f e c t s o f t ime-dependent confound ing f a c t o r s , improv ing the p o s s i b i l i t y t o d e t e c t r e a l c a u s a l a s s o c i a t i o n s . A t h i r d p o s s i b l e r e s e a r c h d e s i g n , which i s used i n t h i s s t udy , i s a combined c r o s s - a r e a / c r o s s - y e a r approach used by Evans e t a l . (1983) i n t h e i r s tudy of the t o t a l B.C. 7 3 p o p u l a t i o n over a s h o r t e r p e r i o d . T h i s de s i gn enab les the c o n t r o l f o r both r e g i o n a l e f f e c t s such as un ique p r a c t i c e s t y l e s and t ime-dependent confound ing f a c t o r s such as g e n e r a l s h i f t s i n m e d i c a l t echno logy o r s u r g i c a l p r a c t i c e . No r e t r o s p e c t i v e r e s e a r c h d e s i g n can demonstrate i n e q u i v o c a l l y what the p a e d i a t r i c i n p a t i e n t u t i l i z a t i o n might have been i n the absence of day c a r e su r ge ry (a h y p o t h e t i c a l s t a t e t h a t never o c c u r r e d ) . On the o t h e r hand, t h i s d e s i g n makes i t p o s s i b l e t o compare s c h o o l d i s t r i c t s w i t h d i f f e r e n t l e v e l s of day c a r e s u r g e r y a v a i l a b i l i t y a f t e r i s o l a t i n g the e f f e c t s of f a c t o r s a f f e c t i n g h o s p i t a l use and v a r y i n g e i t h e r over t ime but common t o a l l d i s t r i c t s , o r a c ro s s d i s t r i c t s but s i m i l a r t o a l l t ime p e r i o d s , t o see i f t h e i r i n p a t i e n t use v a r i e s s y s t e m a t i c a l l y w i t h day ca re su r ge ry a v a i l a b i l i t y . The a b i l i t y t o c o n t r o l f o r the e f f e c t of these o t h e r f a c t o r s i s c r u c i a l i n making i n f e r e n c e s about what i n p a t i e n t u t i l i z a t i o n might have been i n the absence of the growth o f day c a r e s u r g e r y . A l s o , the c r o s s - a r e a / c r o s s - y e a r de s i gn w i l l ensure enough da ta p o i n t s f o r c o n t r o l l i n g s i m u l t a n e o u s l y f o r the many p o s s i b l e con founder s . The adopted r e s e a r c h d e s i g n se t s c e r t a i n da t a r e q u i r e m e n t s . Because the impact o f day ca re su r ge ry a v a i l a b i l i t y on i n p a t i e n t u t i l i z a t i o n i s s t u d i e d both ac ro s s s c h o o l d i s t r i c t s and a c r o s s t i m e , a l l changes i n s c h o o l d i s t r i c t boundar ie s over t ime must be i n c o r p o r a t e d o r r e c o n c i l e d i n computing u t i l i z a t i o n and c a p a c i t y v a r i a b l e s . Fo r t h i s reason a s i n g l e 74 s e t of boundar ie s a t one p o i n t i n t ime was chosen and then a l l o t h e r y e a r s were a d j u s t e d to t h a t s t a n d a r d . In o r d e r to m a i n t a i n c o m p a r a b i l i t y w i th the s i m i l a r s tudy by Evans e t a l . (1983) on the t o t a l p o p u l a t i o n i n B.C., the same method of boundary adjustment was adopted. The adjustment p roce s s was not a s imp le one. because of v a r y i n g d e f i n i t i o n s of s c h o o l d i s t r i c t s a c ro s s a d m i n i s t r a t i v e j u r i s d i c t i o n s . The B.C. M i n i s t r y of H e a l t h , which uses s c h o o l d i s t r i c t s i n cod ing the h o s p i t a l u t i l i z a t i o n d a t a , d e f i n e s the border s somewhat d i f f e r e n t l y than the M i n i s t r y of E d u c a t i o n , and I ndu s t r y and Smal l Bus ines s Development, whose d e f i n i t i o n i s used i n r e p o r t i n g p o p u l a t i o n da ta f o r B.C. The p o p u l a t i o n da t a can be r e c o n s t r u c t e d q u i t e a c c u r a t e l y by g e o g r a p h i c a l a reas u s i n g a v a i l a b l e Census i n f o r m a t i o n and Census Enumerat ion Areas as b u i l d i n g b l o c k s . However, i f boundary changes i n v o l v e o n l y p a r t i a l Enumerat ion A r e a s , p o p u l a t i o n adjustments a re i m p o s s i b l e . The s m a l l e s t g e o g r a p h i c a l u n i t i n h o s p i t a l u t i l i z a t i o n r e c o r d s i s the m u n i c i p a l i t y . Each s c h o o l d i s t r i c t i s d i v i d e d i n t o one t o s i x m u n i c i p a l i t i e s . In most s c h o o l d i s t r i c t s t h e r e a re one o r two p o p u l a t i o n c e n t e r s t h a t have a m u n i c i p a l i t y code and the r e s t of the d i s t r i c t i s r e c o r d e d as m u n i c i p a l i t y ' 0 0 0 ' . I f s c h o o l d i s t r i c t boundary changes i n v o l v e o n l y p a r t i a l m u n i c i p a l i t i e s , as t hey o f t e n do , the r e a l l o c a t i o n of h o s p i t a l u t i l i z a t i o n and c a p a c i t y da ta a c c o r d i n g to the se changes i s i m p o s s i b l e . The problem of c o n t r o l l i n g f o r s c h o o l d i s t r i c t boundary changes over t ime i s made even more c o m p l i c a t e d by the f a c t t h a t the M i n i s t r y of 75 H e a l t h does not always change the s c h o o l d i s t r i c t d e f i n i t i o n s used i n i t s cod ing of h o s p i t a l d i s c h a r g e r e c o r d s each t ime a c t u a l boundar ie s change. In o r d e r t o m in imize the problems i n t h i s adjustment p r o c e s s , the y e a r 1966 was s e l e c t e d f o r the base y e a r i n s t e a d of a more r e c e n t y e a r , and a l l p o p u l a t i o n and u t i l i z a t i o n da ta were brought back t o the 1966 b o u n d a r i e s . However, i f a s c h o o l d i s t r i c t i n e x i s t e n c e i n 1966 was d i v i d e d i n l a t e r y e a r s , t h i s d i v i s i o n was t r i e d t o c a r r y back t o 1966 i f the r e a l l o c a t i o n of the h o s p i t a l r e c o r d s and p o p u l a t i o n da ta was p o s s i b l e . For example, the M i n i s t r y of E d u c a t i o n d e c i d e d t o d i v i d e S l ocan ( s choo l d i s t r i c t no.8) between Ne l son (no. 7) and Arrow Lakes (no. 10) as o f September 1, 1970. The M i n i s t r y o f H e a l t h r e c o g n i z e d t h i s change as of January 1, 1971. Us ing the m u n i c i p a l i t y code i n h o s p i t a l d i s c h a r g e r e c o r d s i t was p o s s i b l e t o i d e n t i f y r e s i d e n t s of S i l v e r t o n and New Denver but not of the r u r a l s u b d i v i s i o n i n the S l ocan s c h o o l d i s t r i c t . In oder t o make h o s p i t a l d i s c h a r g e da ta and p o p u l a t i o n da ta comparable, both the p o p u l a t i o n and d i s c h a r g e s f o r S i l v e r t o n and New Denver were added to Arrow Lakes (no. 10) and the r e s t t o Ne l son (no. 7 ) . T h i s d i v i s i o n was done as of 1966. In cases where s c h o o l d i s t r i c t s were combined a f t e r 1966 i t was u s u a l l y nece s sa ry t o do the combin ing as of 1966, because the p l a c e of r e s i d e n c e i n f o r m a t i o n i n the d i s c h a r g e da ta was too crude f o r s e p a r a t i n g the s c h o o l d i s t r i c t s a f t e r the M i n i s t r y of H e a l t h had changed i t s d i s t r i c t c o d i n g . Fo r example, Ca r i boo (no. 27) and C h i l c o t i n (no. 82) were combined t o form C a r i b o o - C h i l c o t i n (no. 27) as of January 1, 1972. I t 76 was i m p o s s i b l e t o i d e n t i f y r e s i d e n t s f o r Ca r i boo and f o r C h i l c o t i n i n the d i s c h a r g e tapes a f t e r January 1, 1972. F o r t h i s rea son the two s c h o o l d i s t r i c t s were combined as o f 1966. There were a l t o g e t h e r 84 s c h o o l d i s t r i c t s i n 1966, but a f t e r n e c e s s a r y mergers o f some d i s t r i c t s because of the r e a l l o c a t i o n prob lems, the number o f s c h o o l d i s t r i c t s o r u n i t s of o b s e r v a t i o n f o r each yea r i n t h i s s tudy was reduced t o 75 ( F i g u r e 1 ) . The s tudy covered the y e a r s 1968-1976 (same as i n the s tudy by Evans e t a 1. r 1983) and 1981/82-1982/83. The two more r e c e n t y e a r s r e p r e s e n t e d a t ime p e r i o d of d e c r e a s i n g bed c a p a c i t y . The d e t a i l e d d e s c r i p t i o n o f the s c h o o l d i s t r i c t boundary adjustments i s p r e s e n t e d e l sewhere (Evans e t a l . , 1983) . 3.2. Dependent v a r i a b l e - p a e d i a t r i c i n p a t i e n t h o s p i t a l use p e r c a p i t a 3 . 2 . 1 . E x c l u s i o n s f rom numerator The dependent v a r i a b l e i n t h i s s tudy i s h o s p i t a l i n p a t i e n t u t i l i z a t i o n among the p a e d i a t r i c (0-14 yea r s ) p o p u l a t i o n i n B.C. O r i g i n a l l y , the p a e d i a t r i c p o p u l a t i o n was d e f i n e d more b r o a d l y t o i n c l u d e a l s o 15-19 y e a r o l d c h i l d r e n . However, the most common d e f i n i t i o n o f p a e d i a t r i c p o p u l a t i o n i n c l u d e s o n l y the age group 0-14. T h i s i s a l s o the age range t h a t the B.C. FIGURE 1. School d i s t r i c t boundaries in the study. BRITISH COLUMBIA School D i s t r i c t s 1. Fernie 2. Cranbrook 3. Klmberley 4. Windermere 7. Nelson 9. Castlegar 10. Arrow Lakes 11. T r a i l 12. Grand Forks 13. Kettle Valley 14. South Okanagan 15. Pentlcton 16. Keremeos 17. Princeton 18. Golden 19. Revelstoke 20. Saloon Ana 21. Armstrong-Spa Hum 22. Vernon 23. Central Okanagan 24. Kamloops 26. North Thompson 27. Cariboo-Chilcotln 28. Ouesnel 29. L l l l o o e t 30. South Cariboo 31. Merrltt 32. Hope 33. Chilliwack 34. Abbotsford 35. Langley 36. Surrey 37. Delta 38. Richmond 39. Vancouver 40. New Westminster 41. Burnaby 42. Maple Ridge 43. Coqultlam 44. North Vancouver 45. West Vancouver 46. Sechelt 47. Powell River 48. Howe Sound 49. Central Coast 50. Queen Charlotte 52. Prince Rupert 54. Smithere 55. Burns Lake 56. Nechako 57. Prince George 59. Peace River South 60. Peace River North 61. V i c t o r i a 62. Sooke 63. Saanlch 64. Gulf Islands 65. Cowl Chan 66. Lake Cowlchan 67. Ladysmith 68. Nanalao 69. Qualicum 70. Alba m l 71. Courtenay 72. Campbell River 75. Mission 76. Aggasslz 77. Summerland 78. Enderby 80. K l t l o a t 81. Forth Nelson 84. Vancouver Island Vest 85. Vancouver Island North 86. Terrace 87. Stlklne 78 M i n i s t r y of H e a l t h uses i n i t s d e f i n i t i o n o f p a e d i a t r i c f a c i l i t i e s . With o n l y few e x c e p t i o n s , a p a e d i a t r i c ward o r a p a e d i a t r i c bed i s meant o n l y f o r c h i l d r e n l e s s than 15 year s of age. O l d e r c h i l d r e n a r e , i n g e n e r a l , c a red f o r i n a d u l t beds . In cases where a c h i l d has a c h r o n i c i l l n e s s the h o s p i t a l t rea tment may take p l a c e i n a p a e d i a t r i c ward f o r the sake of c o n t i n u i t y of c a r e even when the c h i l d has passed the " p a e d i a t r i c a ge " . With 0-14 y e a r o l d c h i l d r e n , c a r e i n an a d u l t bed i s o n l y a l l owed i n s p e c i a l c i r c u m s t a n c e s , e . g . when a p a e d i a t r i c f a c i l i t y i s not i n d i c a t e d because of the m e d i c a l c o n d i t i o n of the c h i l d , o r i s not e a s i l y i n r e a c h because of the g e o g r a p h i c a l d i s t a n c e . I n c l u s i o n of the 15-19 y e a r o l d age group i n the s tudy would have meant conduc t i n g two s t u d i e s : one f o r the 0-14 y e a r o l d age group u s i n g p a e d i a t r i c bed c a p a c i t y as a measure of bed a v a i l a b i l i t y , and one f o r the 15-19 y e a r o l d age group u s i n g t o t a l bed c a p a c i t y as a measure of bed a v a i l a b i l i t y . The l a t t e r s tudy would have s u f f e r e d from the s m a l l s i z e of the p o p u l a t i o n base i n s c h o o l d i s t r i c t s , which would have i n t r o d u c e d random v a r i a t i o n t o the h o s p i t a l u t i l i z a t i o n measures. A l s o , a c l o s e r look a t the u t i l i z a t i o n p a t t e r n s of the 15-19 yea r o l d age group suggests t h a t t h e i r h o s p i t a l use more c l o s e l y resembles a d u l t u t i l i z a t i o n than p a e d i a t r i c . In 1981/82, the most common d i a g n o s t i c c a t e g o r i e s f o r m e d i c a l s e p a r a t i o n s i n t h i s age group were i n j u r y and p o i s o n i n g (28 p e r c e n t o f a l l m e d i c a l s e p a r a t i o n s ) , d e l i v e r y and pregnancy c o m p l i c a t i o n s (18 pe rcen t ) and menta l d i s o r d e r s (9 p e r c e n t ) . The most common s u r g i c a l p rocedure c a t e g o r i e s 79 were o b s t e t r i c a l p rocedures (27 p e r c e n t of a l l s u r g i c a l s e p a r a t i o n s ) , o p e r a t i o n s on m u s c u l o s k e l e t a l system (25 p e r c e n t ) and o p e r a t i o n s on nose, mouth and pharynx (13 p e r c e n t ) . T h i r t y two p e r c e n t of the day ca re s u r g e r y use i n the 15-19 y e a r o l d age group was f o r a b o r t i o n s . Fo r a l l these r e a s o n s , the 15-19 yea r o l d age group was exc luded from t h i s s tudy . In a d d i t i o n , h o s p i t a l u t i l i z a t i o n by newborns was exc luded s i n c e t h i s group i s not s u b j e c t t o day ca re s u r g e r y . Thus, the p a e d i a t r i c age group t h a t i s d e a l t w i t h i n t h i s s tudy c o n s i s t s of c h i l d r e n from 0 t o 14 year s of age. The s tudy i s r e s t r i c t e d o n l y t o acu te c a r e u t i l i z a t i o n . I t was assumed t h a t c h r o n i c , c o n v a l e s c e n t and r e h a b i l i t a t i o n ca re a r e independent o f day c a r e su r ge ry a v a i l a b i l i t y . Thus, a l l extended c a r e s e p a r a t i o n s , determined by an ' E ' - c o d e i n the computer i zed h o s p i t a l d i s c h a r g e r e c o r d s , were exc luded from the s tudy . U n l i k e extended ca re p a t i e n t s , r e h a b i l i t a t i o n p a t i e n t s c o u l d not be i d e n t i f i e d i n the h o s p i t a l s e p a r a t i o n r e c o r d s . Thus, o n l y those r e h a b i l i t a t i o n cases who were ca red f o r i n r e h a b i l i t a t i o n h o s p i t a l s were exc luded by e x c l u d i n g tho se h o s p i t a l s from the s tudy . R e h a b i l i t a t i o n cases d i s c h a r g e d from acu te ca re h o s p i t a l s remained i n the s tudy . M a t e r n i t y use i s a l s o assumed t o be independent of day ca re s u r g e r y a v a i l a b i l i t y . In o r d e r to sharpen the focus of the 80 s tudy a l l m a t e r n i t y cases ( d e l i v e r y , c o m p l i c a t i o n s o f pregnancy, c h i l d b i r t h , and puerper ium) were exc luded from the s tudy . In 1981/82 t h e r e were 19 such cases i n the p a e d i a t r i c age group. T e r m i n a t i o n s of p regnanc ie s ( a b o r t i o n s ) a re done both on a day c a r e s u r g e r y and on an i n p a t i e n t c a r e b a s i s . Be fo re the imp lementa t i on of amended abo r t i on - law i n Canada on August 26, 1969 t h e r e were v e r y few a b o r t i o n s done i n B r i t i s h Co lumbia . The l e g a l i z a t i o n o f a b o r t i o n c o i n c i d e d w i t h the i n t r o d u c t i o n of day ca re s u r g e r y . A f t e r l e g a l i z a t i o n , a b o r t i o n s have been f r e q u e n t l y done on a day ca re su r ge ry b a s i s . I t can be argued t h a t the i n c r e a s e of day ca re su r ge ry a b o r t i o n s does not r e p r e s e n t a s u b s t i t u t i o n f o r i n p a t i e n t c a r e but i s a g e n e r a t i o n o f new su r ge ry a f t e r a b o l i t i o n o f l e g a l impediments. I t i s l i k e l y t h a t i n the absence of day ca re s u r g e r y i n B.C. h o s p i t a l s the i n c r e a s e d demand f o r a b o r t i o n s would have i nduced a b o r t i o n c l i n i c s . Because of the s p e c i a l c i r cums tance s su r round ing and t i m i n g of the i n c r e a s e i n t e r m i n a t i o n o f p r e g n a n c i e s , i t was f e l t t h a t the r e l a t i o n s h i p between day c a r e su r ge ry and i n p a t i e n t u t i l i z a t i o n r e l a t e d to a b o r t i o n s c o u l d be q u i t e d i f f e r e n t from t h a t w i t h o t h e r p r o c e d u r e s . In o r d e r t o focus the s tudy on the s u b s t i t u t i o n / g e n e r a t i o n e f f e c t s t h a t would n o r m a l l y take p l a c e , the e f f e c t of l e g a l i z a t i o n o f a b o r t i o n and the subsequent i n c r e a s e i n demand were a l s o exc luded from the s tudy by e x c l u d i n g a l l a b o r t i o n s both from the i n p a t i e n t 81 u t i l i z a t i o n and from the day ca re su r ge ry use i n t h i s s tudy . O p e r a t i v e p rocedures i n t h i s c a t e g o r y i n any c a s e , d i d not p l a y a major r o l e i n the h o s p i t a l u t i l i z a t i o n of the p a e d i a t r i c p o p u l a t i o n . In 1981/82 t h e r e were o n l y 25 a b o r t i o n s done on an i n p a t i e n t b a s i s and 76 i n day c a r e s u r g e r y i n B.C. , f o r the p a e d i a t r i c p o p u l a t i o n . 3 .2 .2 . I n c l u s i o n s i n numerator Data on h o s p i t a l u t i l i z a t i o n of B.C. r e s i d e n t s o u t s i d e the p r o v i n c e a re not i n c l u d e d i n the main h o s p i t a l d i s c h a r g e r e c o r d s da tabase . However, t h i s computer i zed database i n c l u d e s h o s p i t a l u t i l i z a t i o n i n B.C. by n o n - r e s i d e n t c h i l d r e n . In o r d e r t o determine the t o t a l h o s p i t a l u t i l i z a t i o n of c h i l d r e n r e s i d i n g i n B .C. , the main database was combined t o a sepa ra te o u t - o f - p r o v i n c e u t i l i z a t i o n da tabase . Add ing o u t - o f - p r o v i n c e u t i l i z a t i o n t o the u t i l i z a t i o n w i t h i n the p r o v i n c e was h i n d e r e d by the f a c t t h a t the o u t - o f - p r o v i n c e da ta were a v a i l a b l e o n l y i n a hard copy form. E x t r a c t i o n o f admis s ions and days of s t a y by s c h o o l d i s t r i c t of r e s i d e n c e , age and sex would have been a l e n g t h y p r o c e s s . Moreover, a c c u r a t e measures o f s u r g i c a l s u b c a t e g o r i e s c o u l d not have been d e r i v e d from these da ta f o r the s tudy purposes because p rocedure codes were not r e c o r d e d . In o r d e r t o overcome these p rob lems , an assumpt ion was made t h a t o u t - o f - p r o v i n c e admi s s ions and days were s i m i l a r l y d i s t r i b u t e d by age, sex and d i f f e r e n t measures of the dependent v a r i a b l e as w i t h i n 82 p r o v i n c e u t i l i z a t i o n . On ly t o t a l number of admi s s ions and days by s c h o o l d i s t r i c t of r e s i d e n c e i n age group 0-14 were e x t r a c t e d . Age, sex and dependent v a r i a b l e d i s t r i b u t i o n s by s c h o o l d i s t r i c t of r e s i d e n c e were d e r i v e d from the w i t h i n p r o v i n c e u t i l i z a t i o n and then a p p l i e d to the o u t - o f - p r o v i n c e u t i l i z a t i o n b e f o r e add ing the o u t - o f - p r o v i n c e f i g u r e s t o the w i t h i n p r o v i n c e u t i l i z a t i o n . A c c e s s i n g o u t - o f - p r o v i n c e u t i l i z a t i o n da t a by s c h o o l d i s t r i c t f o r the y e a r s 1971 and 1973 would have r e q u i r e d an even l e n g t h i e r p roce s s of manual da ta h a n d l i n g . Fur thermore , such da ta d i d not e x i s t a t a l l f o r the y e a r s 1968-1969 and 1982/83. The number of admi s s ions and days by s c h o o l d i s t r i c t were c a l c u l a t e d as the average of the two n e i g h b o u r i n g year s f o r the yea r s 1971 and 1973. Fo r the y e a r s 1968-1969 an assumption was made t h a t t h e i r o u t - o f -p r o v i n c e u t i l i z a t i o n formed the same p r o p o r t i o n of t o t a l i n p a t i e n t u t i l i z a t i o n as i n 1970 and f o r the y e a r 1982/83 i t was assumed t h a t the p r o p o r t i o n was the same as i n 1981/82. T a b l e 4 shows the p r o p o r t i o n o f o u t - o f - p r o v i n c e u t i l i z a t i o n of the t o t a l o u t - and i n - p r o v i n c e u t i l i z a t i o n by s c h o o l d i s t r i c t i n 1971, 1976 and 1981/82. In g e n e r a l , s c h o o l d i s t r i c t s near the A l b e r t a bo rder and, i n p a r t i c u l a r l y , near Edmonton o r G a l g a r y i n A l b e r t a , have a h i g h e r p r o p o r t i o n o f o u t - o f -p r o v i n c e u t i l i z a t i o n . In some cases ( e . g . , Windermere and Golden) r e s u l t s i n 1981/82 (and t o some e x t e n t i n 197 6) r e f l e c t one o r two l ong s t a y admiss ions o u t s i d e the p r o v i n c e . Tab le 4 P ropo r t i on of Ou t -o f -P rov ince U t i l i z a t i o n of the To ta l I n - and Out-Prov ince U t i l i z a t i o n by School D i s t r i c t 1n 1971, 1976, and 1981/82 Admiss ions Days School D i s t r i c t 1971 1976 1981/82 1971 1976 1981/82 1. Fe rn i e 6.28 10.94 4.08 10.65 16.94 12.35 2. Cranbrook 5.83 9.66 5.79 9.02 18.26 12.39 3 . K imber ley 4.74 5.34 4.47 7.22 11.26 21.93 4 . Windermere ' 9.61 5.88 14.09 14.93 27.78 44.22 7. Nelson 1.35 2.39 0.84 1.15 6.34 2.25 9 . Ca s t l ega r 0.80 0.58 0.00 0.75 0.34 0.00 10. Arrow Lakes 0.46 0.91 0.00 0.36 0.38 0.00 11. T r a i l 0.96 1.32 0.89 0.80 3.63 2.22 12. Grand Forks 0.58 1.70 0.69 0.39 1.19 0.33 13. K e t t l e V a l l e y 0.00 0.00 1.85 0.00 0.00 0.48 14. Shouthern Okanagan 0.97 1.32 0.46 0.99 1.05 0.21 15. Pen t i c t on 0.64 2.19 0.95 0.32 2.92 0.64 16. Keremos 1.10 0.00 0.00 1.97 0.00 0.00 17. P r i n ce t on 0.42 0.00 0.00 0.34 0.00 0.00 18. Golden 9.31 14.68 14.19 20.65 43.02 40.14 19. Reve l s toke 1.98 3.62 0.41 2.08 4.20 1.98 20. Salmon Arm 0.51 1.15 1.09 0.33 0.58 1.54 21 . Armstrong Spal lum 0.00 0.72 2.24 0.00 1.12 1.66 22. Vernon 1.54 0.60 1.74 3.75 0.75 1.37 23. Cen t r a l Okanagan 0.84 1.92 1.94 0.96 1.94 1.06 24. Kamloops 1.24 1.25 0.81 1.20 1.14 1.13 26. North Thompson 2.67 3.95 0.61 2.09 9.63 0.52 27. C a r i b o o - C h i l c o t i n 0.73 0.49 0.40 0.35 0.35 0.51 28. Quesnel 1.18 0.83 0.41 0.68 0.55 0.21 29. L i l l o o e t 0.08 0.00 0.31 0.04 0.00 0.17 30. South Car iboo 0.28 0.73 0.71 . 0.12 0.72 0.16 31 . M e r r i t t 0.90 0.25 0.24 0.84 0.05 0.05 32. Hope 0.93 0.43 0.00 0.46 0.13 0.00 33. C h i l l i w a c k 1.01 1.05 0.97 1.12 1.18 1.42 34. Abbots fo rd 1.24 0.86 0.20 1.04 0.93 0.87 35. Lang ley 0.86 0.88 0.60 0.67 0.53 0.48 36. Sur rey 0.74 1.15 0.79 0.60 1.28 0.84 37. De l t a 1.10 1.67 1.24 1.16 1.57 0.53 38. Richmond 0.43 1.51 1.47 0.32 1.49 0.88 39. Vancouver 0.84 1.49 1.38 1.05 1.22 0.92 40. New Westmin is ter 0.82 1.00 1.03 0.77 0.54 0.48 41 . Burnaby 0.84 0.49 0.70 0.53 0.19 0.51 42 . Maple R idge 0.40 0.74 0.66 0.86 0.62 0.37 43. Couqui t lam 0.92 1.63 1.03 0.93 1.36 0.76 44. North Vancouver 1.07 0.76 0.97 1.21 0.60 0.63 45 . West Vancouver 1.15 1.07 1.53 1.24 0.84 0.81 46. Seche l t 0.75 0.95 0.27 0.28 0.78 0.07 84 . . . C o n t i n u e d Table 4 P ropo r t i on of 0ut -o f -Prov1nce U t i l i z a t i o n of the To ta l I n - and Out-P rov ince U t i l i z a t i o n by School D i s t r i c t 1n 1971, 1976, and 1981/82 Admiss ions Days School D i s t r i c t 1971 1976 1981/82 1971 1976 1981/82 47. Powel l R i v e r 0.49 0.54 0.26 0.24 0.24 0.38 48. Howe Sound 0.89 1.10 0.00 0.83 1.10 0.00 49. Cen t r a l Coast 0.13 0.45 0.00 • 0.05 3.29 0.00 50. Queen Cha r l o t t e 1.33 1.53 1.33 1.24 1.24 0.70 52. P r i n ce Rupert 0.55 0.29 0.42 0.55 0.13 0.31 54. Smithers 0.46 2.77 0.00 0.53 3.83 0.00 55. Burns Lake 1.26 0.36 1.16 0.59 0.11 0.70 56. Nechako 0.94 0.35 0.10 0.63 0.07 0.07 57. P r i n ce George 2.32 2.86 1.58 2.18 3.16 2.00 59. Peace R i v e r South 19.75 10.16 3.96 24.25 15.40 4.02 60. Peace R i v e r North 5.52 4.89 2.20 5.81 8.61 1.92 61 . V i c t o r i a 0.94 1.60 0.92 1.02 2.47 0.67 62. Sooke 1.56 1.97 0.87 1.54 1.22 0.59 63. Saanich 0.52 0.30 1.21 0.29 1.05 0.89 64. Gu l f I s l ands 0.95 0.83 1.12 0.48 2.34 1.16 65. Cowichan 0.24 0.08 0.55 0.27 0.11 0.74 66. Lake Cowichan 0.19 0.00 0.00 0.06 0.00 0.00 67. Ladysmith 0.38 0.72 0.24 0.30 0.94 0.05 68. Nanaimo 0.59 0.41 1.22 0.78 0.14 1.32 69. Qual icum 0.00 1.99 0.99 0.00 1.00 0.21 70. A l b e r n i 0.72 0.65 0.60 0.63 1.25 0.33 71 . Courtenay 0.76 1.33 1.18 0.85 1.75 0.76 72. Campbell R i v e r 0.55 1.01 0.74 0.23 0.76 0.75 75. M i s s i on 0.21 1.71 0.65 0.15 1.28 0.45 76. Agas s i z 0.32 0.75 0.00 0.34 1.27 0.00 77. Summerland 0.72 0.00 0.00 0.66 0.00 0.00 78. Enderby 0.82 0.41 0.00 0.79 0.28 0.00 80 . K i t i m a t 0.65 2.21 0.62 0.69 1.64 0.26 8 1 . Fo r t Nelson 1.81 2.54 1.88 1.86 5.44 3.90 84. Vancouver I s l and West 0.40 1.55 0.00 0.54 0.40 0.00 85 . Vancouver I s l and North 1.16 1.12 0.57 0.56 0.91 0.20 86 . Ter race 1.24 2.83 0.39 1.05 5.17 0.20 87. S t i k i n e (+ 88 . Skeena) 2.56 2.73 0.60 2.02 2.05 0.23 To ta l B.C. 1.45 1.73 1.10 1.61 2.24 1.26 3.2.3. Measures of the dependent va r i a b l e numerator In t h i s s tudy , the o v e r a l l impact of day c a r e s u r g e r y i s a s se s sed on both p a e d i a t r i c admiss ions (or s e p a r a t i o n s ) and h o s p i t a l days . The impact of day c a r e su r ge ry on admis s ions may be d i f f e r e n t from the impact on h o s p i t a l days . In the case of s t r a i g h t s u b s t i t u t i o n w i thout any f i l l - i n o f v a c a t e d beds, one would expect admiss ions t o dec rea se by one f o r each day c a r e s u r g e r y case and h o s p i t a l days by 2 t o 4 (Evans and Rob inson , 1973). In the case of s t r a i g h t g e n e r a t i o n o r s u b s t i t u t i o n w i t h complete f i l l - i n o f v a c a t e d beds , n e i t h e r admis s ions nor h o s p i t a l days would show any e f f e c t from day c a r e s u r g e r y . S i t u a t i o n where day ca re su r ge ry would show no n e g a t i v e e f f e c t on admiss ions but s u b s t i t u t i o n e f f e c t on h o s p i t a l days would imp ly f i l l - i n of v a c a t e d beds by p a t i e n t s w i t h s h o r t e r l e n g t h of s t a y than among s u b s t i t u t e d p a t i e n t s , o t h e r t h i n g s b e i n g e q u a l . I f day ca re su r ge ry would show no e f f e c t on h o s p i t a l days but a n e g a t i v e e f f e c t on admi s s i on s , o t h e r t h i n g s b e i n g e q u a l , t h e r e would be s u b s t i t u t i o n w i t h f i l l - i n of v a c a t e d beds by i n c r e a s i n g l eng th s of s t a y of i n p a t i e n t s . On ly a concu r ren t examinat ion of admis s ions and h o s p i t a l days can r e v e a l l e n g t h o f s t a y i n f o r m a t i o n wh ich , i n t u r n , i s u s e f u l i n a s s e s s i n g the p l a u s i b i l i t y o f s u b s t i t u t i o n o r g e n e r a t i o n . Thus dependent v a r i a b l e , h o s p i t a l i n p a t i e n t u t i l i z a t i o n , was measured both as admis s ions and p a t i e n t days per thousand p o p u l a t i o n i n t h i s s tudy . 86 I n p a t i e n t u t i l i z a t i o n was, furthermore, d i v i d e d i n t o s e v e r a l s u b c a t e g o r i e s t o assess whether day care s u r g e r y might have been s u b s t i t u t i n g f o r a t i g h t e r day care e l i g i b l e subset of cases, even i f no d e t e c t a b l e e f f e c t on o v e r a l l u t i l i z a t i o n i s found. Without examining s u b c a t e g o r i e s of i n p a t i e n t u t i l i z a t i o n which have a h i g h e r p o s s i b i l i t y t o be s u b s t i t u t e d by day care surgery, one c o u l d not d i f f e r e n t i a t e s t r a i g h t g e n e r a t i o n from s u b s t i t u t i o n w i t h f i l l - i n of v a c a t e d beds by o t h e r p a t i e n t s , i f no e f f e c t i s found on o v e r a l l i n p a t i e n t u t i l i z a t i o n . Thus, the f o l l o w i n g measures of the dependent v a r i a b l e were c o n s t r u c t e d f o r the study, each being measured both as admissions and h o s p i t a l days i n 0-14 year o l d age-group : 1) MKn/RTTRGi Total m p r l i r a l and surgical inpatient u t i l i z a t i o n (net of m a t e r n i t y , a b o r t i o n and extended care cases). From the medical needs model's p o i n t of view t h i s measure of the dependent v a r i a b l e should show a s i m i l a r response t o day care surgery a v a i l a b i l i t y as a more r e s t r i c t e d measure, such as s u r g i c a l u t i l i z a t i o n , a f t e r a d j u s t i n g f o r o v e r a l l c a p a c i t y c o n s t r a i n t s . S i n c e a l l o t h e r forms of h o s p i t a l u t i l i z a t i o n are determined independently by medical need, an i n c r e a s e i n day care surgery should cause a f a l l i n o v e r a l l u t i l i z a t i o n by the same amount. However, the t o t a l m e d i c a l / s u r g i c a l u t i l i z a t i o n measure of the dependent v a r i a b l e may d i s p l a y a d d i t i o n a l v a r i a n c e u n r e l a t e d t o day care surgery use. 8 7 A c c o r d i n g t o the g e n e r a t i o n h y p o t h e s i s , t he g e n e r a t i o n of new h o s p i t a l use may occu r everywhere. Day c a r e s u r g e r y type p rocedures may f a l l , but o t h e r s u r g i c a l admis s ions i n c r e a s e to occupy the r e l e a s e d space. Or , o v e r a l l s u r g i c a l i n p a t i e n t use may c o n t r a c t somewhat, but m e d i c a l use may expand, such t h a t o v e r a l l h o s p i t a l use i s unchanged. Fo r t h i s reason more than one measure of the dependent v a r i a b l e i s needed t o c a p t u r e the s u b s t i t u t i o n / g e n e r a t i o n e f f e c t s of the day ca re s u r g e r y a v a i l a b i l i t y . 2 ) iSTJRG: Total surgical inpatient nt.il i 7 a t . i n n f which includes only surgical discharges r determined by the presence of an TCP operation code on the discharge form. Cases w i t h n o n - s u r g i c a l o p e r a t i o n codes were exc luded from t h i s measure of the dependent v a r i a b l e (Tab le 5 ) . A c c o r d i n g t o the s u b s t i t u t i o n h y p o t h e s i s t h i s measure shou ld show l e s s u n e x p l a i n e d v a r i a t i o n i n response t o day c a r e s u r g e r y a v a i l a b i l i t y . 3 ) SlJRG-TftA: Total surgical u t i l i z a t i o n net of tons i l l ec tomies (Tonsi l lectomies and Tons i l lectomies with Adenoidectomies). T h i s v a r i a b l e i s , a g a i n , used t o sharpen the focus o f the s tudy by removing from t o t a l s u r g i c a l u se , s u r g i c a l u t i l i z a t i o n t h a t has been d e c l i n i n g f o r reasons m a i n l y u n r e l a t e d t o day ca re su r ge ry a v a i l a b i l i t y . 88 Table 5 Non-operative Procedures Excluded i n This Study-by Different Revisions of International C l a s s i f i c a t i o n of Diseases Code Procedure Canadian Cl a s s i f j r a t i on of Di agnnsr.i o r Therapent i c r and Snrgi ca1 Procedures ( in force 1979 - ) 02.00-02.99 Diagnost ic Radiology and r e l a t e d techniques 03.00-03.99 C l i n i c a l evaluat ion and examination 04.00-04.99 Microscopic examination 05.00-05.99 Other microscopic examination 06.00-06.99 Nuclear medicine 07.00-07.25 Phys ica l medicine, r e h a b i l i t a t i o n , 07.30-07.52 and re la ted 07.54-07.99 procedures 08.00-08.99 Diagnost ic and therapeutic psychology and psychiatry 09.00-09.03 Ophthalmological and o t o l o g i c a l 09.05-09.49 diagnosis and treatment 10.00-10.99 Non-operative in tubat ion , i r r i g a t i o n , and manipulation procedures 11.00-11.04 Replacement and removal 11.14-11.87 therapeutic appliances 13.00-13.99 Other non-operative procedures E i g h t r e v i s i o n of I n t e r n a t i o n a l C l a s s i f i c a t i o n of Diseases ( in force i n 1969-1978) R1.0-R1.9 Radiotherapy and re la ted therapies R4.0-R4.9 Phys ica l medicine and r e h a b i l i t a t i o n R9.0-R9.9 Other nonsurgical procedures Seventh r e v i s i o n of I n t e r n a t i o n a l C l a s s i f i c a t i o n of Diseases ( i n f o r c e i n 1958-1968) 95.0-95.9 Radiat ion therapy 99.0-99.9 Miscel laneous nonsurgical procedures 89 4 ) SURfi A: Inpatient, u t i 1 i s a t i on of s u r g i c a l pa1-.ient.Fi t h a t have undergone one of the procedures t h a t are common i n day care surgery. In order to derive t h i s measure a l i s t of the t h i r t y most common operative procedure categories of paediatric day care surgery i n 1982/1983 were extracted from the day care surgery u t i l i z a t i o n data. A l l procedures within these categories that appeared for at least 40 day care surgery patients i n the 0-14 year old age group were selected to represent the most common day care surgery procedures (Table 6). This l i s t was applied to every study year a f t e r making necessary translations from one rubric of procedure codes to another, to i d e n t i f y a l l s u r g i c a l inpatient discharges that had one of the procedures i n the l i s t . These inpatient discharges formed the basis for u t i l i z a t i o n measures which r e f l e c t p o t e n t i a l day care surgery e l i g i b l e inpatient u t i l i z a t i o n . 5) SURG B: I n p a t i e n t u t i l i s a t i o n by s u r g i c a l p a t i e n t s who had undergone, one of the, p r o c e d u r e s common in day care surgery, whose length of. stay was 5 days or l e s s , and whose combination of primary diagnosis on d i s c h a r g e and procedure rode was a l s o found i n the day care surgery records f o r 19 82/83. i n order to construct t h i s variable a l l the primary diagnoses were l i s t e d by the most common day care surgery procedures from the 1982/83 day care surgery u t i l i z a t i o n data. This combination of diagnosis and length of stay c r i t e r i a was then applied to inpatients included i n the SURG A measure, to 90 Table 6 Most Common Surgical Day Care Procedures i n Paediatric Age Group i n B.C. i n 1982/83 and Their Multiplication Factors for SURG C Measure1 Procedure ICD 7 C o d e 2 ICD 8 CLD 20.4 20.4 20.4 17.0 17.0 17.0 32.01 32.09 32.10 24.1 24.1 24.2 24 .6 99.3 99.3 99.4 99.9 35.01 35.09 35.19 35.20 35.49 90.6 A4.6 1.34 69.2 61.2 76.00 89.0 92.0 98.04 89.1 92.1 98.12 89-4 89.2 92.5 92.4 98.22 98.96 40.0 40.0 40 . 6 38.2 38.2 38.8 65.01 65.21 65.49 27.2 27.3 21.2 21.3 40.20 40.50 82.0 82.3 84.0 84.4 91.01 82.6 83.3 91.02 7.29 11.0 11.2 10.5 23.10 11.3 18.5 18.5 10.6 6.5 6.5 23.20 21.32 21.33 Myringotomy w i t h i n s e r t i o n o f tube (1.00) Other myringotomy (1.00) Forceps e x t r a c t i o n of dec iduous t o o t h (0) Fo rceps e x t r a c t i o n of o t h e r t o o t h (0) Other s u r g i c a l e x t r a c t i o n of t o o t h (0) R e s t o r a t i o n o f t o o t h by f i l l i n g (0) (1.00) Other n o n - o p e r a t i v e cy s to s copy (0.86) C i r c u m c i s i o n (1.00) I n c i s i o n w i t h removal of f o r e i g n body of s c i n and subcutaneous t i s s u e (0) L o c a l e x c i s i o n p r d e s t r u c t i o n of l e s i o n o r t i s s u e o f s k i n and s u c u t i s (0.20) Su ture of s k i n and subcutaneous t i s s u e (exc ludes l i p and e x t e r n a l mouth) (0) Removal of n a i l b e d (1.00) R e p a i r o f i n g u i n a l h e r n i a (0.40) B i l a t e r a l r e p a i r of i n g u i n a l h e r n i a (0.49) R e p a i r o f u m b i l i c a l h e r n i a (1.00) T o n s i l l e c t o m y w i t h adenoidectomy (0) Adenoidectomy w i thou t t o n s i l l e c t o m y (0.43) C l o s e d r e d u c t i o n o f f r a c t u r e (without i n t e r n a l f i x a t i o n ) - humerus (0) C l o s e d r e d u c t i o n of f r a c t u r e s (wi thout i n t e r n a l f i x a t i o n ) - c a r p a l s and metaca rpa l s (1.00) Other f o r c i p l e c o r r e c t i o n of d e f o r m i t y (1.00) E x c i s i o n of l e s i o n o r t i s s u e o f o c u l a r musc les o r tendons (1.00) Advancement o r r e c e s s i o n of o c u l a r musc les (1.00) P r o b i n g of l a c r i m a l t r a c t (1.00) (1.00) 91 T a b l e 6 ( cont inued) Hos t Common S u r g i c a l Day Care Procedures i n P a e d i a t r i c Age Group i n B.C. i n 1982/83 and T h e i r M u l t i p l i c a t i o n F a c t o r s f o r SURG C M e a s u r e 1 Procedure ICD 7 Code 2 ICD 8 CLD Meatotomy (1.00) R e p a i r and p l a s t i c o p e r a t i o n s on u r e t h r a (1.00) 64 64 .1 .4 57 .1 57.4 70. 70. 10 36 Other o p e r a t i o n s on nose (1.00) Reduc t i on ( c l o sed ) of n a s a l f r a c t u r e (1.00) 21 21 .9 .5 19.5 19.4 33. 33. 03 61 E x c i s i o n o f l e s i o n o f musc le , tendon and f a s c i a (1.00) 85 .2 88.2 94. 21 C o r r e c t i o n o f prominent ea r (1.00) 20 20 .2 .3 16.5 12. 21 Removal o f c h a l a z i o n (1.00) 12 12 .1 .2 7.1 7.2 22. 11 L i n g u a l f renotomy (1.00) 26 .0 96.1 37. 91 S u r g i c a l c o r r e c t i o n of o f prominent e a r (1.00) 20 .2 94.0 30. 40 A r t h r o s c o p y (0.66) - - 92. 85 Orch iopexy (0.75) 67 .7 59.7 74. 40 Re t rog rade pyelogram (0) 93 .2 A9.1 67. 86 Other s inusotomy (1.00) 21 .6 19.7 34. 00 M y r i n g o p l a s t y (1.00) 20 .4 17.6 17 .9 31. 40 R i gh t c a r d i a c c a t h e t e r i z a t i o n (0) 30 .4 30.2 49. 95 Eye examina t ion under a n e s t h e s i a (1.00) - - 9. 04 1> M u l t i p l i c a t i o n f a c t o r s a re i n b r a c k e t s . 2> Codes: ICD 7 = I n t e r n a t i o n a l C l a s s i f i a c t i o n of D i s e a s e s , 7th r e v i s i o n ; ICD 8 = I n t e r n a t i o n a l C l a s s i f i c a t i o n o f D i s e a s e s , 8th r e v i s i o n ; CLD = Canadian C l a s s i f i c a t i o n of D i a g n o s t i c , T h e r a p e u t i c , and S u r g i c a l P r o c e d u r e s . 92 s e l e c t the u t i l i z a t i o n t h a t r e f l e c t e d day care s u r g e r y e l i g i b l e diagnoses and procedures w i t h lengths of s t a y of 5 days o r l e s s . The t r a n s l a t i o n of d i a g n o s t i c codes from one r u b r i c t o another was r e s t r i c t e d t o the f i r s t t h r e e d i g i t s . 6) SURG C.i T h i s was the most r e s t r i c t i v e day c a r e s u r g e r y e l i g i b l e .inpatient u t i l i z a t i o n measure. T h i s measure was d e r i v e d by a s k i n g surgeons s p e c i a l i z i n g i n performing the procedures i n c l u d e d i n the SURG A measures t o look a t the p r o c e d u r e / d i a g n o s i s / l e n g t h of s t a y combinations of cases i n SURG B and t o g i v e t h e i r judgements as t o what p r o p o r t i o n of t h i s u t i l i z a t i o n c o u l d e q u a l l y w e l l have been done on a day care s u r g e r y b a s i s . T h i s judgement was obt a i n e d i n 1983. A l l the surgeons i n t e r v i e w e d were working a t the B.C. C h i l d r e n ' s H o s p i t a l i n Vancouver, and were s e l e c t e d on a b a s i s of t h e i r s p e c i a l t y t o cover a l l the procedures i n c l u d e d i n the SURG A measure. M u l t i p l i c a t i o n f a c t o r s d e r i v e d t h i s way were then a p p l i e d t o a l l study years t o d e r i v e the SURG C u t i l i z a t i o n measure from SURG B f i g u r e s (Table 6 ) . These s i x measures of the dependent v a r i a b l e were used t o t e s t the same h y p o t h e s i s , t h a t day care surgery a v a i l a b i l i t y has an independent and s i g n i f i c a n t n e g a t i v e e f f e c t on i n p a t i e n t h o s p i t a l u t i l i z a t i o n among a p a e d i a t r i c p o p u l a t i o n , r e g a r d l e s s of the h o s p i t a l bed c a p a c i t y a v a i l a b l e . 93 3 .2 .4 . Denominator of t h e dependent v a r i a b l e A l l measures of the dependent v a r i a b l e as w e l l as a l l independent v a r i a b l e s e x c l u d i n g soc ioeconomic v a r i a b l e s were exp re s sed i n pe r c a p i t a terms f o r the s c h o o l d i s t r i c t s . The denominator of a l l measures of the dependent v a r i a b l e was the number of 0-14 y e a r o l d c h i l d r e n i n the s c h o o l d i s t r i c t . S i nce the numerator and the denominator of the dependent v a r i a b l e both r e f e r t o the same s c h o o l d i s t r i c t of r e s i d e n c e , the b i a s e s t h a t have been o f t e n r e l a t e d t o these k i n d o f s m a l l a rea s t u d i e s were avo ided (D iehr , 1984). 3 .2 .5 . Age- sex adjustment of t h e dependent v a r i a b l e In o r d e r t o c o n t r o l f o r p o s s i b l e d i f f e r e n c e s i n age- sex d i s t r i b u t i o n i n the 0-14 y e a r o l d age group a c r o s s s c h o o l d i s t r i c t s and over t i m e , a l l the measures of the dependent v a r i a b l e were a d j u s t e d t o the 1981 p r o v i n c i a l age - sex d i s t r i b u t i o n . S i n c e age and sex a re s t r o n g l y r e l a t e d t o h o s p i t a l u t i l i z a t i o n , age-sex adjustment c o n t r o l s f o r one impor tan t source of s y s temat i c b i a s . The adjustment p roces s c r e a t e d measures of u t i l i z a t i o n f o r each s c h o o l d i s t r i c t as i f i t s p o p u l a t i o n age/sex mix had been t h a t of the p r o v i n c e i n 1981, but i n c u r r e d t h a t s c h o o l d i s t r i c t ' s a g e / s e x - s p e c i f i c u t i l i z a t i o n e x p e r i e n c e . The age-groups used f o r the adjustment were 0, 1-4, 5-9 and 10-14. The adjustment p rocedure f o r admi s s ions was: 94 u < « o = 2 _ 13 Pl3 P. 3 P. . and f o r the h o s p i t a l days : — D i 3 P.3 u«*> = * i 3 P i j P.-where C i j and D i 3 a re admiss ions and days of s t a y , r e s p e c t i v e l y , f o r the j t h age-sex group r e s i d e n t s o f s c h o o l d i s t r i c t i ; P i 3 i s the number of c h i l d r e n i n the j t h age-sex group i n d i s t r i c t i ; P.3 i s the number of c h i l d r e n i n B.C. i n the j t h age- sex group a c c o r d i n g to the 1981 Census, and P.. i s t o t a l p r o v i n c i a l p o p u l a t i o n i n the 0-14 y e a r o l d age group i n 1981. In s m a l l e r s c h o o l d i s t r i c t s the adjustment p roces s encountered some prob lems, because the age by sex p o p u l a t i o n da ta t h a t were a v a i l a b l e had been randomly rounded t o 5 o r 10. F o r s m a l l s c h o o l d i s t r i c t s , w i t h v e r y s m a l l numbers i n age -group 0, t h i s can have a l a r g e e f f e c t on apparent u t i l i z a t i o n r a t e s , wh i ch , when weighted by p r o v i n c i a l p r o p o r t i o n s f o r summation, can s h i f t s i g n i f i c a n t l y the e n t i r e d i s t r i c t u t i l i z a t i o n r a t e . In o r d e r t o m in imize t h i s e f f e c t any d i s t r i c t / a g e / s e x c e l l v a l u e which c o n t a i n e d l e s s than 25 c h i l d r e n was c o n s o l i d a t e d w i t h i t s immediate ne i ghbour . 95 3.3. Independent v a r i a b l e s 3 . 3 . 1 . Day c a r e s u r g e r y a v a i l a b i l i t y (DCS) The main independent v a r i a b l e i s the day c a r e s u r g e r y a v a i l a b i l i t y f o r the p a e d i a t r i c p o p u l a t i o n , as an exogenous o r p o l i c y v a r i a b l e whose impact on i n p a t i e n t u t i l i z a t i o n i s t o be measured. Day ca re su r ge ry a v a i l a b i l i t y was measured as the t o t a l p a e d i a t r i c day ca re su r ge ry u t i l i z a t i o n (net o f m a t e r n i t y and a b o r t i o n cases ) pe r 1,000 p o p u l a t i o n . There appears t o be no s a t i s f a c t o r y measure of the day c a r e su r ge ry c a p a c i t y , as opposed to u t i l i z a t i o n . N o n - o p e r a t i v e p rocedures were exc luded from the day ca re su r ge ry u t i l i z a t i o n the same way as t hey were exc luded from the s u r g i c a l measures of the dependent v a r i a b l e . The day ca re s u r g e r y u t i l i z a t i o n measure was age- sex s t a n d a r d i z e d u s i n g the same adjustment p rocedure as f o r i n p a t i e n t admi s s i on s . The day ca re s u r g e r y da ta from 1968-1970 i n c l u d e d o n l y broad age c a t e g o r i e s and no da ta on sex and s c h o o l d i s t r i c t o f r e s i d e n c e . The da ta were l i s t e d o n l y by h o s p i t a l of s e r v i c e f o r the t o t a l 0-14 y e a r o l d age group. T h i s posed two prob lems: age d i s a g g r e g a t i o n , and r e s i d e n c e d e t e r m i n a t i o n . An assumpt ion was made t h a t the p a t t e r n o f day ca re s u r g e r y p a t i e n t f lows ac ro s s s c h o o l d i s t r i c t boundar ie s (an o r i g i n - d e s t i n a t i o n ma t r i x ) was the same i n 1968-1970 as i t was observed i n 1971. The o r i g i n - d e s t i n a t i o n m a t r i x was d e r i v e d f o r the y e a r 1971 and i t took the form: Six . . • • S 1 j • • . .Sin S i l . . . .Si j . . . Siri. Srxl • • ••SnJ•• where S i 3 i s the number of day ca re su r ge ry cases from s c h o o l d i s t r i c t i who r e c e i v e d ca re i n h o s p i t a l s l o c a t e d i n s c h o o l d i s t r i c t j , and n i s the t o t a l number of s c h o o l d i s t r i c t s i n the p r o v i n c e . The day c a r e su r ge ry u t i l i z a t i o n f o r each s c h o o l d i s t r i c t i n the 0-14 y e a r o l d age group was then c a l c u l a t e d as f o l l o w s f o r the y e a r 1970: DCS 70, i -S 7 i , * S 70 , . 3 171, .3 where S 7 i , i 3 i s the observed number of day c a r e s u r g e r y p a t i e n t s from s c h o o l d i s t r i c t i , c a red f o r by h o s p i t a l s i n s c h o o l d i s t r i c t j i n 1971; S 7 i , . j i s the t o t a l number o f day c a r e s u r g e r y cases c a red f o r i n s c h o o l d i s t r i c t j (= S 7 i , i j summed a c r o s s a l l i ) , and S?o,.j i s the observed number of day c a r e s u r g e r y p a t i e n t ca red f o r i n 1970 by h o s p i t a l s i n s c h o o l d i s t r i c t j . The same c a l c u l a t i o n was used a l s o f o r the year s 1968 and 1969. 97 The age and sex d i s a g g r e g a t i o n of the day ca re s u r g e r y u t i l i z a t i o n f o r each s c h o o l d i s t r i c t f o r 1968-1970 was done by assuming t h a t the age-sex d i s t r i b u t i o n i n those yea r s was the same as i n 1971. Age-sex adjustment was then c a r r i e d out as f o r o t h e r y e a r s and measures of the dependent v a r i a b l e . 3 .3 .2 . H o s p i t a l bed a v a i l a b i l i t y (BEDS) The supp l y model o f h o s p i t a l u t i l i z a t i o n i m p l i e s t h a t the a v a i l a b i l i t y of day c a r e su r ge ry as an expans ion i n o v e r a l l h o s p i t a l c a p a c i t y would i n c r e a s e the o v e r a l l s u r g i c a l o r h o s p i t a l use ( i n p a t i e n t p l u s day c a r e s u r g e r y ) , but perhaps lower i n p a t i e n t u se , depending on whether o r not t h e r e i s any s u b s t i t u t i o n w i thou t f i l l - i n g e n e r a t i o n . T h i s g e n e r a t i o n e f f e c t cannot be s t u d i e d w i thout i n c l u d i n g h o s p i t a l system c a p a c i t y i n the u t i l i z a t i o n e q u a t i o n . The bed a v a i l a b i l i t y v a r i a b l e i s h y p o t h e s i z e d to be the main con found ing f a c t o r i n a n a l y z i n g the r e l a t i o n s h i p between day ca re su r ge ry and i n p a t i e n t u t i l i z a t i o n , s i n c e i t may be c a u s a l l y r e l a t e d both t o day c a r e su r ge ry u t i l i z a t i o n and t o i n p a t i e n t u t i l i z a t i o n . In t h i s s tudy the number of o f f i c i a l l y - r e p o r t e d p a e d i a t r i c h o s p i t a l beds pe r 1,000 p o p u l a t i o n was s e l e c t e d f o r the measure of h o s p i t a l bed a v a i l a b i l i t y . I t i s i m p o s s i b l e to de termine the a c t u a l p r o p o r t i o n of c h i l d r e n t h a t have been c a r e d f o r i n a d u l t beds because a d m i s s i o n - s e p a r a t i o n r e c o r d s c o n t a i n no i n d i c a t i o n of the type of bed ( p a e d i a t r i c o r 98 a d u l t ) . However, t h i s p r o p o r t i o n i s b e l i e v e d t o be s m a l l . Sheps (1980) has e s t ima ted t h a t l e s s than 0.5 p e r c e n t of c h i l d r e n 10-14 a re admi t ted to a d u l t r a t h e r than p a e d i a t r i c r a t e d beds. In o r d e r t o e s t ima te the number o f beds t h a t non -p a e d i a t r i c h o s p i t a l s c o n t r i b u t e t o the o v e r a l l bed c a p a c i t y a v a i l a b l e f o r the 0-14 y e a r o l d s , p a e d i a t r i c u t i l i z a t i o n was s t u d i e d s e p a r a t e l y f o r h o s p i t a l s t h a t d i d not have approved p a e d i a t r i c beds. Both t o t a l days and the number of days consumed by 0-14 y e a r o l d s were c a l c u l a t e d i n each of these h o s p i t a l s i n B .C. , and then a p r o p o r t i o n of t o t a l a cu te ca re beds used by the p a e d i a t r i c group was de te rm ined . These " u n o f f i c i a l " p a e d i a t r i c beds amounted t o 0.9 p e r c e n t o f the o f f i c i a l p a e d i a t r i c bed c a p a c i t y i n 1971, 2.3 p e r c e n t i n 1976 and 2.9 p e r c e n t i n 1981/82 i n B.C. Because the se beds p l a y o n l y a minor r o l e i n the o v e r a l l p a e d i a t r i c bed c a p a c i t y , a d e c i s i o n was made not t o i n c l u d e d these i n the BEDS v a r i a b l e . 3 . 3 . 2 . 1 . Adjustment f o r boundary c r o s s i n g (B~) H o s p i t a l beds p h y s i c a l l y l o c a t e d i n a s c h o o l d i s t r i c t a re not e x c l u s i v e l y used by s c h o o l d i s t r i c t r e s i d e n t s , nor a re they the o n l y beds to which r e s i d e n t s of any p a r t i c u l a r s c h o o l d i s t r i c t have a c c e s s . In o r d e r to overcome t h i s problem a " s y n t h e t i c " bed count was c o n s t r u c t e d f o r each s c h o o l d i s t r i c t . T h i s measure r e f l e c t s the beds a c t u a l l y used by the r e s i d e n t s of the s c h o o l d i s t r i c t , wherever they might be l o c a t e d . F i r s t , a p a t i e n t o r i g i n - d e s t i n a t i o n m a t r i x was 99 d e r i v e d from the i n p a t i e n t u t i l i z a t i o n da tabase . T h i s m a t r i x shows the number of p a t i e n t days (acute c a r e , e x c l u d i n g m a t e r n i t y and a b o r t i o n s ) used by the r e s i d e n t s o f a s c h o o l d i s t r i c t , i n t h e i r own d i s t r i c t and i n each o t h e r d i s t r i c t i n the p r o v i n c e . I t t akes the form: D n • • . . D i j . • • .Din D i i . . . .Di j . . . .Din Dnl....DnJ••••Dnn where D A J i s the number of days o f c a r e r e c e i v e d by r e s i d e n t s of s c h o o l d i s t r i c t i i n h o s p i t a l beds l o c a t e d i n s c h o o l d i s t r i c t j , and n i s the t o t a l number o f s c h o o l d i s t r i c t s i n the p r o v i n c e . The o r i g i n - d e s t i n a t i o n m a t r i x , c a l c u l a t e d f o r each y e a r i n the s tudy , was then a p p l i e d t o the v e c t o r of beds a c t u a l l y l o c a t e d i n each s c h o o l d i s t r i c t . The f o l l o w i n g c a l c u l a t i o n was used t o d e r i v e the number of " s y n t h e t i c " beds i n s c h o o l d i s t r i c t i : '13 x B-D, Di. (0.8)(365) Where Bj i s t he number of beds (approved p a e d i a t r i c beds) i n s c h o o l d i s t r i c t j and D i 3 i s t he number o f p a t i e n t days r e c e i v e d by r e s i d e n t s i n s c h o o l d i s t r i c t i i n h o s p i t a l beds l o c a t e d i n s c h o o l d i s t r i c t j . The symbol D.j i s the sum of 100 the ( D u + D 2 J + D 3 3 . . . + D 7 s , j ) v a l u e s a c ro s s a l l 75 s c h o o l d i s t r i c t s i n the p r o v i n c e , p l u s D 7 s , 3 f o r o u t - o f - p r o v i n c e r e s i d e n t s who have r e c e i v e d ca re i n s c h o o l d i s t r i c t j . U t i l i z a t i o n by the o u t - o f - p r o v i n c e r e s i d e n t s , D 7 s , a , i s not i n the numerator of the p r o p o r t i o n m u l t i p l i e d by B 3 . In t h i s way beds used by o u t - o f - p r o v i n c e r e s i d e n t s a r e removed from c a p a c i t y a v a i l a b l e f o r B.C. r e s i d e n t s anywhere i n the p r o v i n c e . The symbol DA,-7 6 i s the number of days of c a re i n o u t - o f - p r o v i n c e h o s p i t a l s r e c e i v e d by r e s i d e n t s of s c h o o l d i s t r i c t i . S i n c e t h e r e i s no way t o d e f i n e the exac t bed c a p a c i t y a v a i l a b l e t o B.C. r e s i d e n t s o u t s i d e the p r o v i n c e , an assumpt ion was made t h a t the o u t - o f - p r o v i n c e bed c a p a c i t y a v a i l a b l e equa l s the c a p a c i t y t h a t has been a c t u a l l y u sed , assuming an average occupancy r a t e of 80 p e r c e n t i n t h a t c a p a c i t y . Thus, each 292 days o f o u t - o f - p r o v i n c e c a r e i s c o n s i d e r e d one a v a i l a b l e o u t - o f - p r o v i n c e bed. In o t h e r words, i t i s assumed t h a t o u t - o f - p r o v i n c e use has always taken p l a c e i n a p a e d i a t r i c f a c i l i t y . The a r b i t r a r i l y s e l e c t e d occupancy r a t e i s h i g h e r than i n p a e d i a t r i c f a c i l i t i e s i n B.C. because i t i s assumed t h a t h o s p i t a l beds o u t s i d e the p r o v i n c e a r e , i n g e n e r a l , not as e a s i l y a v a i l a b l e as w i t h i n the p r o v i n c e . Tab le 7 shows the d i f f e r e n c e s between a c t u a l and s y n t h e t i c bed counts by s c h o o l d i s t r i c t i n 1971, 1976 and 1981/82. In 1971 and 1976, B.C. had a net g a i n o f p a e d i a t r i c beds a f t e r a d j u s t i n g f o r t r a n s f e r s of bed a v a i l a b i l i t y a c r o s s the Table 7 Number of Actual and Synthetic Paediatric Beds by School District in B.C. in 1971. 1976. and 1981/82 1971 1976 1981/82 Actual Synthetic Actual Synthetic Actual Synthetic School District beds beds beds beds beds beds 1. Fernie 4 6.08 6 10.77 11 13.10 2. Cranbrook 12 12.98 12 12.32 12 9.23 3. Kimberley 5 7.52 5 6.13 5 5.14 4. Windermere 5 6.04 5 5.95 5 5.03 7. Nelson 11 12.46 11 14.33 11 12.78 9. Castlegar 10 12.68 10 11.99 4 5.73 10. Arrow Lakes 5 6.01 5 7.17 4 6.18 11. Trail 28 19.89 18 11.66 15 11.17 12. Grand Forks 4 3.17 4 4.28 4 4.84 13. Kettle Valley 0 1.74 0 3.29 0 1.35 14. Shouthern Okanagan 4 6.41 6 8.74 6 8.53 15. Penticton 20 14.18 15 12.99 15 10.70 16. Keremos 0 2.97 0 0.80 0 0.82 17. Princeton 4 4.02 0 1.45 0 1.00 18. Golden 3 4.15 5 7.04 5 4.87 19. Revelstoke 6 8.32 6 7.60 6 7.85 20. Salmon Arm 5 9.65 7 11.83 7 10.28 21. Armstrong Spa Hum 0 2.44 0 2.21 0 2.99 22. Vernon 20 17.92 22 19.00 22 18.00 23. Central Okanagan 28 30.16 28 28.38 23 24.41 24. Kamloops 50 39.73 50 41.94 48 35.99 26. North Thompson 0 5.20 0 2.37 0 3.05 27. Cariboo-Chilcotin 23 33.71 31 42.07 31 42.74 28. Quesnel 18 21.48 18 21.45 14 19.02 29. Lillooet 12 12.05 12 12.99 12 13.31 30. South Cariboo 19 22.24 16 18.29 8 11.64 31. Herritt 12 13.86 12 14.74 12 15.61 32. Hope 4 8.18 8 10.08 8 9.61 . C o n t i n u e d Table 7 Number of Actual and Synthetic Paediatric Beds by School District in B.C. in 1971. 1976. and 1981/82 1971 1976 1981/82 Actual Synthetic Actual Synthetic Actual Synthetic School District beds beds beds beds beds beds 33. Chilliwack 19 18.15 19 21.1b 19 20.63 34. Abbotsford 14 18.82 14 19.24 16 21.39 35. Langley 16 18.97 24 35.24 24 34.77 36. Surrey 31 61.71 53 73.39 53 69.02 37. Delta 0 24.12 0 35.04 0 26.37 38. Richmond 26 40.76 26 37.84 26 36.07 39. Vancouver 371 181.10 322 123.22 278 96.92 40. New Westminister 96 18.50 94 17.02 45 8.41 41. Burnaby 37 61.93 37 54.25 37 38.22 42. Maple Ridge 21 23.67 23 31.70 24 30.43 43. Couquitlam 0 50.09 0 48.86 0 25.14 44. North Vancouver 44 41.65 44 36.11 24 24.15 45. West Vancouver 0 9.45 0 8.96 0 5.88 46. Sechelt 6 8.13 6 8.35 6 9.12 47. Powell River 19 22.36 19 22.13 12 14.64 48. Howe Sound 2 7.63 4 10.88 3 7.70 49. Central Coast 19 17.25 5 7.08 3 3.49 50. Queen Charlotte 7 9.50 7 10.03 3 5.46 52. Prince Rupert 24 26.15 31 26.51 31 27.10 54. Smithers 25 17.06 23 17.99 23 20.33 55. Burns Lake 14 13.42 20 24.51 20 24.91 56. Nechako 9 15.22 13 16.65 13 19.17 57. Prince George 70 73.64 71 72.96 67 61.32 59. Peace River South 20 25.28 21 23.99 21 21.94 60. Peace River North 21 27.59 21 26.63 21 26.29 61. Victoria 106 67.67 131 74.96 129 78.38 62. Sooke 0 17.90 0 21.71 0 17.91 63. Saanich 6 14.40 6 17.88 6 14.93 64. Gulf Islands 3 3.97 3 4.39 3 4.11 65. Cowichan 29 30.55 32 39.05 32 35.68 . C o n t i n u e d ' Table 7 Number of Actual and Synthetic Paediatric Beds by School District in B.C. in 1971, 1976. and 1981/82 1971 1976 1981/82 Actual Synthetic Actual Synthetic Actual Synthetic School District beds beds beds beds beds beds 66. Lake Cowichan 0 6.34 0 4.85 0 3.58 67. Ladysmith 13 14.57 13 14.87 4 9.48 68. Nanaimo 27 21.55 27 24.08 22 19.53 69. Qualicum 0 3.55 0 3.65 0 4.13 70. Alberni 25 32.67 30 39.75 16 27.92 71. Courtenay 15 20.54 11 13.27 11 16.12 72. Campbell River 10 13.29 12 17.20 12 12.76 75. Mission 10 10.50 10 14.63 10 14.73 76. Agassiz 0 4.60 0 3.90 0 3.18 77. Sumnerland 3 3.89 3 3.51 3 5.13 78. Enderby 6 4.75 6 6.68 0 2.07 80. Kitimat 18 21.41 17 22.44 14 18.65 81. Fort Nelson 12 13.41 9 10.21 11 12.64 84. Vancouver Island West 0 4.22 0 3.95 0 3.68 85. Vancouver Island North 21 28.99 16 21.86 13 19.94 86. Terrace 6 10.27 4 6.75 4 7.76 87. Stikine (+ 88. Skeena) 44 59.17 30 45.30 32 42.79 Total B.C. 1577 1585.59 1569 1576.46 1379 1368.92 Net gain (loss) of paediatric 8.59 7.46 (10.08) beds outside the province 104 p r o v i n c i a l b o r d e r . But i n 1981/82 t h e r e was a net l o s s of 10 p a e d i a t r i c beds, a l though a c t u a l bed count i n B.C. had dec rea sed marked ly . T o t a l number of p a e d i a t r i c beds made a v a i l a b l e f o r o u t - o f - p r o v i n c e user s d i d not v a r y much from y e a r t o y e a r (15-17 p a e d i a t r i c b e d s ) , but between 1976 and 1981 t h e r e was a marked decrease i n the number of p a e d i a t r i c beds used by B.C. r e s i d e n t s o u t - o f - p r o v i n c e (from 23-24 beds t o around 5 b e d s ) . Tab le 7 shows a l s o the e f f e c t s of i n t e r -d i s t r i c t t r a n s f e r s of p a e d i a t r i c bed a v a i l a b i l i t y , on the b a s i s of a c t u a l u se . These t r a n s f e r s have e s p e c i a l l y s t r i k i n g e f f e c t i n Vancouver . For example, i n 1981/82, o f 278 p a e d i a t r i c beds i n the d i s t r i c t , o n l y 96.92 a re a l l o c a t e d t o d i s t r i c t r e s i d e n t s . Tab le 7 i n d i c a t e s t h a t , over t i m e , Vancouver beds have been i n c r e a s i n g l y used by o u t - o f - d i s t r i c t p a t i e n t s . 3.3.2.2. Adjustment f o r non-homogeneous p o p u l a t i o n (P*) P o p u l a t i o n s a re non-homogeneous i n r e s p e c t t o age-sex s t r u c t u r e . A s c h o o l d i s t r i c t w i t h a r e l a t i v e l y e l d e r l y p o p u l a t i o n would be expected t o need and use more h o s p i t a l c a p a c i t y . In such s c h o o l d i s t r i c t s an a p p a r e n t l y h i g h b e d - t o -p o p u l a t i o n r a t i o might s t i l l r e p r e s e n t t i g h t c a p a c i t y i f i t were not h i g h enough t o meet the above average needs of the p o p u l a t i o n . The same a p p l i e s t o p a e d i a t r i c beds , but the age e f f e c t i s j u s t r e v e r s e d . The younger the p a e d i a t r i c p o p u l a t i o n the h i g h e r the r e l a t i v e need f o r beds, s i n c e i n f a n t s and 1-4 105 years o l d c h i l d r e n have h i g h e r h o s p i t a l u t i l i z a t i o n r a t e s than o l d e r c h i l d r e n . D i f f e r e n c e s i n demographic s t r u c t u r e w i t h i n the p a e d i a t r i c p o p u l a t i o n between s c h o o l d i s t r i c t s and over time may b i a s the estimated c o e f f i c i e n t s on the p a e d i a t r i c bed a v a i l a b i l i t y measure. In o r d e r t o minimize t h i s p o s s i b l e b i a s , the s y n t h e t i c bed count d e r i v e d f o r the 0-14 year age group was d i v i d e d by an a d j u s t e d s c h o o l d i s t r i c t p a e d i a t r i c p o p u l a t i o n . The a d j u s t e d p o p u l a t i o n estimates the p o p u l a t i o n i m p l i e d by an assumption of c o n s t a n t i n t e r - d i s t r i c t and i n t e r - t e m p o r a l a g e - s e x - s p e c i f i c h o s p i t a l use f o r the a c t u a l age-sex mix i n each d i s t r i c t and time p e r i o d . In oth e r words, i f a c t u a l p a e d i a t r i c p o p u l a t i o n does not change, but t h e r e i s a mix s h i f t t o younger, h i g h e r per c a p i t a use c h i l d r e n , the a d j u s t e d p o p u l a t i o n w i l l be b i g g e r than a c t u a l t o r e f l e c t h i g h e r expected h o s p i t a l use, g i v e n unchanged a g e - s e x - s p e c i f i c u t i l i z a t i o n per c a p i t a . Thus, the a d j u s t e d p o p u l a t i o n accounts not o n l y f o r a c t u a l p o p u l a t i o n changes, but a l s o f o r changes i n the age-sex mix as they would a f f e c t h o s p i t a l u t i l i z a t i o n . T h i s a d j u s t e d p o p u l a t i o n denominator f o r the s y n t h e t i c BEDS v a r i a b l e (B") was c a l c u l a t e d f o r each s c h o o l d i s t r i c t by summing a c r o s s the number of c h i l d r e n i n each age-sex category, weighted by t h e i r province-wide r e l a t i v e u t i l i z a t i o n r a t e s i n a base year. The year 1981 was s e l e c t e d f o r the base year. The c a l c u l a t i o n was: x P D. . " ( 8 1 ) 106 Where PAJ i s the number of c h i l d r e n i n s c h o o l d i s t r i c t i , and age- sex c l a s s j . P . j ( 8 i ) i s the t o t a l number o f c h i l d r e n i n age- sex group j i n a l l o f B .C. , by the 1981 Census, and D . j ( B i ) i s the t o t a l number o f h o s p i t a l days of c a r e r e c e i v e d by c h i l d r e n i n B.C. i n age-sex group j i n 1981/82, wherever r e c e i v e d . P . . < e i > and D..<BIJ a r e t o t a l p r o v i n c i a l p a e d i a t r i c p o p u l a t i o n by the 1981 Census, and days o f c a r e r e c e i v e d by t h a t p o p u l a t i o n i n 1981/82. Tab le 8 shows the a c t u a l and a d j u s t e d p o p u l a t i o n s by s c h o o l d i s t r i c t i n 1971, 1976 and 1981/82. The d i f f e r e n c e between a c t u a l and a d j u s t e d p o p u l a t i o n s i n 1981/82 i s caused by the s l i g h t d i f f e r e n c e between the 1981 Census p o p u l a t i o n (as o f b e g i n n i n g o f June) and the 1981/82 mid f i s c a l yea r p o p u l a t i o n ( e x t r a p o l a t e d t o the b e g i n n i n g of O c t o b e r ) . The f i n a l measure of the p a e d i a t r i c bed a v a i l a b i l i t y i n t h i s s tudy was B*/P*, which i s , f o r now on, c a l l e d the BEDS measure. 3 .3 .3 . Number o f p h y s i c i a n s p e r c a p i t a (DOCS) A p h y s i c i a n s p e r c a p i t a r a t i o was i n c l u d e d i n the s tudy f o r c o n t r o l l i n g f o r p o t e n t i a l con found ing e f f e c t s a s s o c i a t e d w i t h p h y s i c i a n a v a i l a b i l i t y . Number of p h y s i c i a n s a v a i l a b l e t o the p a e d i a t r i c p o p u l a t i o n may have an independent e f f e c t , both on the l e v e l o f day ca re su r ge ry u t i l i z a t i o n , and on the i n p a t i e n t u t i l i z a t i o n r a t e . In t h i s , i t may a c t as a Table 8 Actual and Adjusted Populations for 0-14 Age Group by School district in 1971. 1976. and 1981/82 1971 1976 1981/82 Actual Adjusted Actual Adjusted Actua1 Adjusted 1. Fernie 3.550 3.658 4.445 4.412 4.765 5,010 2. Cranbrook 4.805 4.716 5.290 4.951 5.759 5.721 3. Kimberley 2.595 2.406 2,200 2.101 2.167 2.066 4. Windermere 1.610 1.559 1.535 1.473 1.584 1.770 7. Nelson 5.200 4.852 5,100 4.885 4.866 4.825 9. Castlegar 3.250 3.011 3,105 2.794 2.982 2.979 10. Arrow Lakes 1.155 1.114 1,195 1.139 1.217 1.191 11. Trail 6.330 5,966 5.200 4,829 4,800 4.754 12. Grand Forks 1.555 1.418 1.505 1.337 1.489 1.544 13. Kettle Valley 775 680 825 789 717 651 14. Shouthern Okanagan 2.465 2,183 2.280 2.133 2.664 2.708 15. Penticton 5.265 4,636 5,425 5.041 5,056 4,941 16. Keremos 650 559 690 593 728 750 17. Princeton 995 905 1.255 1.210 1.041 984 18. Golden 2.265 2.211 1.860 1.742 1,608 1,662 19. Revelstoke 2.820 2.730 2.645 2.577 2.527 2.585 20. Salmon Arm 4.435 4.012 5.075 4.750 5,358 5.378 21. Armstrong Spallum 1.190 981 1,520 1.404 1.760 1.731 22. Vernon 7.555 6.848 9.330 8.855 9,773 9.638 23. Central Okanagan 14.155 13.165 17.255 15,830 17.362 16.580 24. Kamloops 17.575 16.302 20.105 18.967 19.593 19.115 26. North Thompson 1.220 1.240 1.515 1.561 1.472 1.398 27. Cariboo-Chilcotin 7.960 7,859 9.710 9.528 10.308 10.645 28. Quesnel 5.945 5.734 6,515 6.223 6,372 6,440 29. Lillcoet 1.445 1.436 1.340 1.340 1,248 1,346 30. South Cariboo 2.860 2.716 2,390 2.288 2,266 2,251 31. Merritt 3.120 3.028 2.935 2.718 2,686 2.647 32. Hope 1.980 1.814 1.950 1.827 1,860 1,883 33. Chilliwack 10.045 8.981 9.850 9.180 9.649 9.486 34. Abbotsford 9.475 8.878 10,775 10.316 13,601 14.148 35. Langley 8,340 7.967 13.605 13.373 15,899 15,458 36. Surrey 33.545 30.894 33,305 32.474 38.228 39,666 37. Delta 16.515 16,113 20.860 19.554 20.462 18.921 38. Richmond 19.860 18.100 20,615 19.917 21.180 20.988 39. Vancouver 84.300 81.123 68,185 65.149 59.999 61,371 40. New Westminister 8.340 8.430 5.650 5.615 4.599 5.001 41. Burnaby 32.105 30.453 26,070 24.695 22.255 22,648 42. Maple Ridge 8,220 7.774 9,225 8.916 9.684 9.898 43. Couquitlam 29.045 27.470 25,950 24.061 24.392 24.142 44. North Vancouver 25.730 24.311 21,505 19.873 18.086 17.617 45. West Vancouver 8.930 7.458 6.960 5.796 5.905 5.407 46. Sechelt 2.590 2.514 2,920 2.800 3.497 3.661 . C o n t i n u e d Table 8 Actual and Adjusted Populations for 0-14 Age Group by School district in 1971. 1976. and 1981/82 1971 1976 1981/82 Actual Adjusted Actual Adjusted Actua 1 Adjusted 47. Powell River 5.945 5.696 5,485 5,153 4.361 4.068 48. Howe Sound 3.185 3,169 3,380 3.346 3.908 4.095 49. Central Coast 1.495 1.376 1.390 1,366 852 953 50. Queen Charlotte 1.595 1.618 1.775 1,800 1.584 1.624 52. Prince Rupert 5.870 6.045 5,080 5,006 4,953 5,000 54. Smithers 3.895 3.949 3.665 3.609 4.294 4.386 55. Burns Lake 2,180 2.097 2,480 2,376 2.479 2.574 56. Nechako 4.245 4.043 4.620 4.646 5.062 5,159 57. Prince George 23.730 23,274 25,690 25.302 25.493 25.718 59. Peace River South 7.615 7.133 6.375 5,899 6.284 6.455 60. Peace River North 7,380 7.013 6,920 6.685 8.153 8.637 61. Victoria 34.565 31.581 28.760 26.652 25.405 25.431 62. Sooke 8,085 7.725 9.185 8.729 9.115 8.805 63. Saanich 5.915 5.428 6.780 6.172 7.128 6.957 64. Gulf Islands 890 845 1.125 1.043 1.268 1.178 65. Cowichan 7.400 6.709 7,905 7.579 7.899 7.664 66. Lake Cowichan 1.935 1,860 1.675 1.656 1.472 1.500 67. Ladysmith 2.840 2.675 2.785 2.555 2,881 2.861 68. Nanaimo 11,145 10.135 11.665 10.881 12,534 12.672 69. Qualicum 1.895 1.630 2.590 2,503 3.859 3.931 70. Alberni 10.405 10.189 9.350 9.058 8.246 7.940 71. Courtenay 7,805 6.909 7.550 6.903 8.100 7,881 72. Campbell River 6,105 5.787 6.515 6.340 7.315 7.434 75. Mission 3.710 3.405 5.040 5,175 6.299 6.247 76. Agassiz 1,280 1.208 1.180 1,103 1.086 1.089 77. Sunmerland 1.290 1.175 1.415 1.235 1,410 1.254 78. Enderby 1.045 925 1.260 1.239 1.218 1.159 80. Kitimat 5.120 5.042 4.490 4.413 4,489 4.544 81. Fort Nelson 1.410 1.485 1.560 1.505 1.501 1.586 84. Vancouver Island West 1.505 1.634 1.365 1.396 1.444 1.416 85. Vancouver Island North 3.565 3,597 3.925 3.985 4.342 4.720 86. Terrace 3.345 3.015 2.890 2.663 2.661 2.621 87. Stikine (+ 88. Skeena) 9.815 9,829 9.455 9.206 9.083 9.169 Total B.C. 610.010 576.398 594.970 566.067 587.638 588.342 109 con found ing f a c t o r when s t u d y i n g the r e l a t i o n s h i p between the two. The p h y s i c i a n - t o - p o p u l a t i o n r a t i o was measured both as the t o t a l f u l l - t i m e e q u i v a l e n t (FTE) p h y s i c i a n s pe r 10,000 p a e d i a t r i c p o p u l a t i o n (DOCS) and as F T E - a d j u s t e d number of p h y s i c i a n s i n f i v e d i f f e r e n t s p e c i a l t y c a t e g o r i e s p e r 10,000 p a e d i a t r i c p o p u l a t i o n . In o r d e r t o d e r i v e these measures, a l l p h y s i c i a n s who appeared on the h o s p i t a l d i s c h a r g e r e c o r d s , e i t h e r as the a d m i t t i n g o r o p e r a t i n g p h y s i c i a n f o r a 0-14 yea r o l d c h i l d , were i d e n t i f i e d . A l s o , d e n t i s t s u n d e r t a k i n g o r a l s u r g e r y i n h o s p i t a l s on p a t i e n t s of t h i s age were i n c l u d e d i n the l i s t . Then t h i s l i s t of p h y s i c i a n s (or a c t u a l l y t h e i r M e d i c a l S e r v i c e s Commission numbers) was l i n k e d to the M e d i c a l S e r v i c e s P l a n b i l l i n g da ta i n o r d e r t o get the s p e c i a l t y i n f o r m a t i o n f o r each p h y s i c i a n and t o c a l c u l a t e a FTE v a l u e f o r each d o c t o r . Fo r year s p r i o r t o 1976 the l i s t of p h y s i c i a n s was d e r i v e d from the d i s c h a r g e r e c o r d s on a c a l e n d a r y e a r b a s i s , but the b i l l i n g i n f o r m a t i o n was based on f i s c a l y e a r s . Adjustment f o r t h i s d i f f e r e n c e was not c o n s i d e r e d e s s e n t i a l , s i n c e i t had been shown t h a t i t does not change the f i g u r e s s i g n i f i c a n t l y (Evans et. a 1 . f 1983). FTE v a l u e s were c a l c u l a t e d u s i n g a method deve loped by the Hea l th Manpower Research U n i t i n B.C. (Barer and Wong Fung, 1985). By t h i s method, each p h y s i c i a n r e c e i v i n g payments equa l t o o r g r e a t e r than o n e - h a l f the payment mean f o r h i s / h e r peer type of p r a c t i c e = 1 FTE ; a l l o the r s a re counted as the p r o p o r t i o n 110 of t h e i r r e c e i p t s t o the mean r e c e i p t s o f t h e i r f u l l - t i m e type of p r a c t i c e p e e r s . I f a p h y s i c i a n ' s s p e c i a l t y was unknown he was a s s i g n e d an FTE v a l u e of one, s i n c e h i s r e f e r e n c e peers c o u l d not be de te rm ined . The FTE v a l u e c a l c u l a t e d f o r each p h y s i c i a n was " p a r t i t i o n e d " among s c h o o l d i s t r i c t s a c c o r d i n g to the r e s i d e n c e of h i s 0-14 y e a r o l d p a t i e n t s . T h i s p a r t i t i o n i n g o r a l l o c a t i o n of FTE va l ue s ac ro s s d i s t r i c t s was done on b a s i s of p a e d i a t r i c h o s p i t a l r e c o r d s . For a g i v e n y e a r , i f a l l h o s p i t a l i z e d c h i l d r e n of a p h y s i c i a n appea r i ng on the h o s p i t a l d i s c h a r g e database were r e s i d e n t s of the same s c h o o l d i s t r i c t , then t h a t p h y s i c i a n counted as h i s FTE v a l u e i n t h a t s c h o o l d i s t r i c t and zero e l sewhere . I f p a e d i a t r i c i n p a t i e n t s were drawn e q u a l l y from two d i s t r i c t s , the p h y s i c i a n ' s FTE was s p l i t h a l f and h a l f between the d i s t r i c t s , and so on. However, a w e i g h t i n g f o r p h y s i c i a n s ' t ime and e f f o r t was done i n t h i s p r o c e s s . I f a p h y s i c i a n appeared on the d i s c h a r g e da ta as a d m i t t i n g p h y s i c i a n of a p a t i e n t , the p a t i e n t was g i v e n a we ight of 0.25. I f he appeared as o p e r a t i n g p h y s i c i a n , the p a t i e n t was g i v e n a weight of 0.75 and i f the p h y s i c i a n had both admi t ted and opera ted on the p a t i e n t , the p a t i e n t was counted as one. T h i s we i gh t i n g of p a t i e n t s was done i n a l l o c a t i n g p h y s i c i a n s a c ro s s s c h o o l d i s t r i c t s . The purpose of t h i s w e i g h t i n g was to i n d i c a t e the p r o p o r t i o n of each p h y s i c i a n ' s h o s p i t a l - b a s e d t ime and e f f o r t made a v a i l a b l e to r e s i d e n t s o f each s c h o o l d i s t r i c t . The a d m i t t i n g / v i s i t i n g I l l proce s s may not r e p r e s e n t as much e f f o r t o r c a p a c i t y commitment as the o p e r a t i o n i t s e l f . The weights t h a t were used t o d i f f e r e n t i a t e the a v a i l a b l e c a p a c i t y were a r b i t r a r i l y chosen, but seemed p l a u s i b l e to p h y s i c i a n s (Evans e t a 1. f 1983). These weights do not a f f e c t o v e r a l l measures o f p h y s i c i a n a v a i l a b i l i t y , because each p h y s i c i a n s t i l l counts as h i s FTE i n t o t a l . On ly t h e i r p a r t i t i o n i n g among s c h o o l d i s t r i c t s i s a l t e r e d i f t h e i r r a t i o o f admis s ions t o o p e r a t i o n s d i f f e r s s i g n i f i c a n t l y a c c o r d i n g t o the r e s i d e n c e of the p a t i e n t . F i n a l l y , the a l l o c a t e d FTEs were summed i n each s c h o o l d i s t r i c t of p a t i e n t and d i v i d e d by the p a e d i a t r i c p o p u l a t i o n o f the s c h o o l d i s t r i c t . No p o p u l a t i o n adjustment f o r changes i n age-sex mix a c ro s s d i s t r i c t s and over t ime was u sed . The same approach was used to c a l c u l a t e the s p e c i a l t y -s p e c i f i c measures of p h y s i c i a n a v a i l a b i l i t y , but the c a l c u l a t i o n s were done s e p a r a t e l y f o r each s p e c i a l t y c a tego ry . P h y s i c i a n s were c l a s s i f i e d i n t o the f o l l o w i n g s p e c i a l t y c a t e g o r i e s : 1) g e n e r a l and f a m i l y p r a c t i t i o n e r s (GP); 2) p a e d i a t r i c i a n s (PAED); 3) s u r g i c a l s p e c i a l t i e s (SURGEON), which i n c l u d e s g e n e r a l s u r g e r y , neu ro su r ge ry , o r t h o p a e d i c s u r g e r y , p l a s t i c s u r g e r y , t h o r a c i c s u r g e r y , u r o l o g y , d e n t a l s u r g e r y , o b s t e t r i c s and gynaeco logy , optha lmology , and e a r , nose and t h r o a t ; 112 4) a n a e s t h e s i o l o g i s t s (ANA); and 5) o t h e r s p e c i a l t i e s (OTHER). I f a p h y s i c i a n ' s s p e c i a l t y was unknown he was put i n t o the c a t e g o r y OTHER. The s p e c i a l t y and b i l l i n g i n f o r m a t i o n was not a v a i l a b l e p r i o r t o the y e a r 1972. The s p e c i a l t y i n f o r m a t i o n i n 1972/73 b i l l i n g da ta was found t o be i n c o m p l e t e . I t was thus d e c i d e d t o c a l c u l a t e the F T E - a d j u s t e d p h y s i c i a n - t o - p o p u l a t i o n measure (DOCS) and d i f f e r e n t p h y s i c i a n by s p e c i a l t y measures (GP, PAED, SURGEON, ANA, and OTHER) o n l y f o r the yea r s 1973 and on, and not t o i n c l u d e any p h y s i c i a n a v a i l a b i l i t y measures f o r the y e a r s 1968-1972 i n the s tudy . The adjustment procedure i n a l l o c a t i n g p h y s i c i a n s a c ro s s s c h o o l d i s t r i c t s was done o n l y f o r the yea r s 1974 and on , because o n l y a d m i t t i n g p h y s i c i a n appeared i n the d i s c h a r g e r e c o r d s i n the e a r l i e r y e a r s . Fo r the y e a r 1973 an assumption was made t h a t the a d m i t t i n g p h y s i c i a n would have been the o p e r a t i n g p h y s i c i a n , and each p a t i e n t was counted as one. 3 .3 .4 . Soc ioeconomic v a r i a b l e s These v a r i a b l e s were i n c l u d e d i n the s tudy as p r o x i e s f o r h o s p i t a l c a re need i n the p a e d i a t r i c p o p u l a t i o n , on the r a t i o n a l e t h a t i n t e r - d i s t r i c t v a r i a t i o n i n h o s p i t a l 113 u t i l i z a t i o n may be a r e f l e c t i o n o f the v a r i a t i o n i n demographic, s o c i a l and economic c h a r a c t e r i s t i c s o f the s c h o o l d i s t r i c t p o p u l a t i o n s . The e f f e c t of the most i n f l u e n t i a l demographic f a c t o r , age-sex d i s t r i b u t i o n of the p a e d i a t r i c p o p u l a t i o n , i s a l r e a d y been i n c o r p o r a t e d by age- sex adjustment of the dependent v a r i a b l e and the DCS v a r i a b l e , and p o p u l a t i o n mix adjustment of the BEDS v a r i a b l e . However, s e v e r a l o t h e r c h a r a c t e r i s t i c s of the p o p u l a t i o n may a l s o p l a y a r o l e i n d e t e r m i n i n g h o s p i t a l u t i l i z a t i o n r a t e s . The soc ioeconomic da ta f o r the s c h o o l d i s t r i c t s were d e r i v e d from the 1971 and 1981 Censuses by Census Enumerat ion A r e a s . These Census Enumerat ion Areas were then a l l o c a t e d t o a p p r o p r i a t e s c h o o l d i s t r i c t s t o c o n s t r u c t the v a l u e o f each soc ioeconomic v a r i a b l e i n each s c h o o l d i s t r i c t . Va lues of the soc ioeconomic v a r i a b l e s d e r i v e d from the 1971 Census were g i v e n a l s o to s c h o o l d i s t r i c t s i n 1968-1970 and 1972-1976 and v a l u e s from the 1981 Census were extended a l s o t o the y e a r 1982/83 i n the c r o s s - a r e a / c r o s s - y e a r a n a l y s i s of the d a t a . T h i s d e c i s i o n was based on an assumpt ion t h a t s o c i a l , demographic and economic c h a r a c t e r i s t i c s of a p o p u l a t i o n do not change v e r y q u i c k l y over t i m e ; i n any even t , t he se were the o n l y a v a i l a b l e da ta of t h i s s o r t . B a s i c a l l y the same se t of soc ioeconomic v a r i a b l e s was i n c l u d e d i n the s tudy as i n the e a r l i e r s tudy by Evans e t a l . (1983). The v a r i a b l e s i n c l u d e d were: 114 1) Percentage of p o p u l a t i o n born i n Canada (CAN). 2) Percentage of p o p u l a t i o n whose mother tongue was E n g l i s h (MTENG). 3) Percentage of p o p u l a t i o n who were of Ind ian o r Eskimo e t h n i c i t y (IND). 4) Percentage of p o p u l a t i o n l i v i n g i n r u r a l a reas (RURAL), where r u r a l was d e f i n e d a s : a l l p a r t s of i n c o r p o r a t e d r u r a l m u n i c i p a l i t i e s and unorgan ized t e r r i t o r i e s , I nd ian r e s e r v e s hav ing a p o p u l a t i o n d e n s i t y of l e s s t h a t 400 per square k i l o m e t e r , and i n c o r p o r a t e d c i t i e s , towns and v i l l a g e s w i th a p o p u l a t i o n of l e s s than 1000. 5) Percentage of p o p u l a t i o n , 15 year s and o l d e r , who had l e s s than grade 5 e d u c a t i o n ( i n 1971 Census) o r l e s s than grade 9 e d u c a t i o n ( i n 1981 Census) (EDUC). Because the c l a s s i f i c a t i o n of e d u c a t i o n was somewhat d i f f e r e n t i n the 1971 and 1981 Census t a p e s , the EDUC v a r i a b l e i s not e x a c t l y comparable i n 1971 and 1981. Fo r t h i s reason the EDUC v a r i a b l e was omi t ted from the poo led c r o s s - a r e a / c r o s s - y e a r a n a l y s i s and i n c l u d e d o n l y i n the s i n g l e y e a r c ro s s s e c t i o n a l ana l y se s f o r year s 1971 and 1981/82. 6) Average number of rooms per d w e l l i n g (ROOMS). T h i s v a r i a b l e was c a l c u l a t e d by c a l c u l a t i n g f i r s t the t o t a l number of rooms i n p r i v a t e d w e l l i n g s i n each enumerat ion a rea i : t o t a l rooms( i )= average number of rooms( i ) * number of p r i v a t e d w e l l i n g s ( i ) 115 The average number of rooms per d w e l l i n g i n s c h o o l d i s t r i c t j was then c a l c u l a t e d by summing t o t a l rooms of a l l enumerat ion a reas i n s c h o o l d i s t r i c t j and d i v i d i n g t h a t by t o t a l number of d w e l l i n g s i n s c h o o l d i s t r i c t j . 7) Average t o t a l income of p o p u l a t i o n 15 yea r s and o l d e r ( INC). In o r d e r t o d e r i v e t h i s v a r i a b l e , the average per c a p i t a income of persons aged 15 and over i n each enumerat ion a r e a was m u l t i p l i e d by the p o p u l a t i o n over 14 yea r s of age i n t h a t enumerat ion a r e a . These e s t ima te s o f t o t a l income i n each enumerat ion a rea were then added ac ro s s a l l enumerat ion areas i n the s c h o o l d i s t r i c t . F i n a l l y the t o t a l income of the s c h o o l d i s t r i c t was d i v i d e d by the p o p u l a t i o n , 15 yea r s and o v e r , i n the s c h o o l d i s t r i c t . Fo r the a n a l y s i s of poo led c r o s s -a rea / c r o s s - y e a r da ta the average income i n the 1971 Census was a d j u s t e d t o the 1981 l e v e l u s i n g the Vancouver consumer p r i c e i n d e x . 8) Percentage of l a b o r f o r c e unemployed (UNEM). 9) Percentage of the e x p e r i e n c e d l a b o r f o r c e who had wh i te c o l l a r o c c u p a t i o n s (WHITE), where wh i te c o l l a r o ccupa t i on s were d e f i n e d a s : manager i a l and a d m i n i s t r a t i v e o c c u p a t i o n s ; t e a c h i n g o c c u p a t i o n s ; o ccupa t i on s i n med i c ine and h e a l t h ; t e c h n o l o g i c a l , s o c i a l , r e l i g i o u s and a r t i s t i c o c c u p a t i o n s ; c l e r i c a l o c c u p a t i o n s ; s a l e s and s e r v i c e o c c u p a t i o n s ; and r e l a t e d o c c u p a t i o n s . 10) Percentage of e x p e r i e n c e d l a b o r f o r c e i n v o l v e d i n p r imary i n d u s t r i e s (PRIM), where p r imary i n d u s t r y was d e f i n e d a s : 116 a g r i c u l t u r e ; f o r e s t r y ; f i s h i n g and t r a p p i n g ; mines , q u a r r i e s and o i l w e l l s . 3 .4 . Data sources The a n a l y t i c v a r i a b l e s i n t h i s s tudy were drawn from s e v e r a l s o u r c e s . Each o f the main databases i n v o l v e d i s d e s c r i b e d b r i e f l y below. 3 . 4 .1 . A d m i s s i o n - s e p a r a t i o n database f o r i n p a t i e n t use U n t i l 1982/83 H o s p i t a l Programs i n the B.C. M i n i s t r y of H e a l t h r e c e i v e d a completed a d m i s s i o n - s e p a r a t i o n r e c o r d f o r each p a t i e n t c a r e d f o r i n a h o s p i t a l i n the p r o v i n c e . These r e c o r d s were keypunched c e n t r a l l y by H o s p i t a l Programs and s t o r e d on magnet ic t a p e s . The l o g i c and u n i f o r m i t y of the da ta were checked a t the t ime of keypunch ing . Fo r example, the u n i f o r m i t y i n cod ing the p r i n c i p a l and secondary d iagnoses o r p rocedures were examined. T h i s method of da ta c o l l e c t i o n and s t o r i n g dec rea sed the p o s s i b i l i t y t h a t v a r i a t i o n of d i f f e r e n t measures of independent v a r i a b l e s a c ro s s s c h o o l d i s t r i c t s i s due t o v a r i a t i o n i n r e c o r d i n g and c o d i n g . A f t e r 1982/83 the . maintenance of da ta i n t e g r i t y was d e c e n t r a l i z e d . Thus, 1982/83 may be the l a s t y e a r of da ta s u i t a b l e f o r t h i s t ype of c r o s s -a rea compar i son , w i thou t runn ing i n t o d i f f i c u l t i e s w i t h c o m p a r a b i l i t y of the da ta (Sauter and Hughes, 1983). 117 I n f o rma t i on on p a t i e n t s ' p l a c e of r e s i d e n c e ( s choo l d i s t r i c t and m u n i c i p a l i t y ) , age, sex, l e n g t h of s t a y , p r i n c i p a l d i a g n o s i s and type of p r i n c i p a l o p e r a t i o n were d e r i v e d from t h i s database f o r the numerator o f each measure of the dependent v a r i a b l e . The M e d i c a l S e r v i c e s Commission number f o r the a d m i t t i n g and o p e r a t i n g p h y s i c i a n s was e x t r a c t e d f o r the p h y s i c i a n - t o - p o p u l a t i o n v a r i a b l e . 3 .4 .2 . A d m i s s i o n - s e p a r a t i o n database f o r day c a r e s u r g e r y S i n c e 1971, H o s p i t a l Programs i n the M i n i s t r y of H e a l t h has a l s o r e c e i v e d a r e c o r d of each day ca re s u r g e r y case i n B.C. h o s p i t a l s . These r e c o r d s , which c o n t a i n e s s e n t i a l l y the same i n f o r m a t i o n as the a d m i s s i o n - s e p a r a t i o n r e c o r d f o r i n p a t i e n t s , were a l s o keypunched and s t o r e d on magnet ic tape i n the same manner as the i n p a t i e n t d a t a . The numerator o f the main independent v a r i a b l e , the day ca re s u r g e r y a v a i l a b i l i t y , was d e r i v e d from t h i s da tabase . The day ca re su r ge ry u t i l i z a t i o n da ta d i d not e x i s t p r i o r t o 1971 i n the form of i n d i v i d u a l p a t i e n t r e c o r d s . The da ta f o r the year s 1968-1970 were more l i m i t e d . I n fo rmat i on was o n l y a v a i l a b l e on t o t a l number of cases by h o s p i t a l and by broad age ca tego ry (0-14, 15-44, 45 -69, and 70+). 118 3 .4 .3 . O u t - o f - p r o v i n c e u t i l i z a t i o n H o s p i t a l Programs keeps r e c o r d s o f o u t - o f - p r o v i n c e h o s p i t a l i n p a t i e n t u t i l i z a t i o n by B.C. r e s i d e n t s . However, as noted e a r l i e r the da ta a re a v a i l a b l e o n l y i n a hard copy form. For 1970, 1972, 1974-1976 and 1981/82 o u t - o f - p r o v i n c e d i s c h a r g e s were l i s t e d by s c h o o l d i s t r i c t of r e s i d e n c e and then by h o s p i t a l o f s e r v i c e . Fo r the yea r s 1971 and 1973 the d i s c h a r g e s were f i r s t l i s t e d by h o s p i t a l o f s e r v i c e , and o b t a i n i n g u t i l i z a t i o n i n f o r m a t i o n by s c h o o l d i s t r i c t of r e s i d e n c e would have been a l eng thy p r o c e s s . O u t - o f - p r o v i n c e i n p a t i e n t u t i l i z a t i o n da ta were not a v a i l a b l e p r i o r t o 197 0 and not i n 1982/83, e i t h e r . A c c o r d i n g to H o s p i t a l Programs, t h e r e i s no i n f o r m a t i o n r e a d i l y a v a i l a b l e on the o u t - o f -p r o v i n c e day c a r e su r ge ry use by B.C. r e s i d e n t s . Because of the na tu re of t h i s type of s u r g e r y , the o u t - o f - p r o v i n c e u t i l i z a t i o n i s assumed t o be v e r y s m a l l . O u t - o f - p r O v i n c e i n p a t i e n t u t i l i z a t i o n da ta were used to complete the numerator f o r the measures o f the dependent v a r i a b l e and t o a d j u s t the measures of bed c a p a c i t y a v a i l a b l e t o B.C. r e s i d e n t s . 3 .4 .4 . P o p u l a t i o n and soc ioeconomic d a t a The p o p u l a t i o n da ta by s c h o o l d i s t r i c t i n B.C. a r e made a v a i l a b l e by the M i n i s t r y of I ndus t ry and Sma l l Bus ines s 119 Development, but the boundar ies used a re not those d e f i n e d by the M i n i s t r y o f H e a l t h but the M i n i s t r y o f E d u c a t i o n . Because of the c o n f u s i o n t h a t the two d e f i n i t i o n s o f s c h o o l d i s t r i c t s caused , the M i n i s t r y of H e a l t h has r e c e n t l y renamed i t s s c h o o l d i s t r i c t s L o c a l H e a l t h A r e a s . Evans e t a l . (1983) d i d a c o n s i d e r a b l e amount o f da ta m a n i p u l a t i o n i n o r d e r t o d e r i v e p o p u l a t i o n f i g u r e s f o r M i n i s t r y of H e a l t h s c h o o l d i s t r i c t s and t o mod i fy these da ta t o the 1966 b o u n d a r i e s . In o r d e r t o a v o i d r e p e a t i n g the same work, the p o p u l a t i o n f i g u r e s t h a t were p r o v i d e d by t h e i r s tudy were used a l s o i n t h i s s tudy f o r the y e a r s 1968-1976. Fo r t h i s r e a s o n , a l s o , the adjustment p rocedure f o r a l l o c a t i n g h o s p i t a l u t i l i z a t i o n da ta i n t o the 1966 boundar ie s was done the same way as i t was done i n the p r e v i o u s s tudy . The p o p u l a t i o n da ta f o r the s c h o o l d i s t r i c t s used i n t h i s s tudy were not r e a d i l y a v a i l a b l e f o r the yea r s 1981/82 and 1982/83. In o r d e r t o d e r i v e these d a t a , a l i s t o f 1981 Census Enumerat ion Areas by M i n i s t r y of E d u c a t i o n s c h o o l d i s t r i c t s was o b t a i n e d from the M i n i s t r y of I ndus t r y and Smal l Bus iness Development. The enumerat ion areas i n t h i s l i s t were then n e s t e d i n t o the s c h o o l d i s t r i c t boundar ie s t h a t were used i n t h i s s tudy . Because s c h o o l d i s t r i c t boundar ie s i n e f f e c t i n 1976 were s t i l l the same i n 1981/82 and 1982/83, most of the n e s t i n g was done by comparing the 1981 Census Enumerat ion Areas t o the l i s t s of 1976 enumerat ion a reas i n each s tudy d i s t r i c t , p r o v i d e d by the p r e v i o u s s tudy (Evans e t a l . f 1983). 120 However, the enumerat ion a rea boundar ie s change from one census t o ano the r . In cases where a 1981 enumerat ion a rea d i d not match the 1976 enumerat ion a rea b o u n d a r i e s , the n e s t i n g was done by l o o k i n g a t the a c t u a l l o c a t i o n o f the enumerat ion a rea on a map and de te rm in ing the s c h o o l d i s t r i c t t o which i t be l onged . The 1981 Census Enumerat ion Area l i s t i n g by s c h o o l d i s t r i c t s used i n t h i s s tudy was used t o e x t r a c t the p o p u l a t i o n f i g u r e s by age and sex from the 1981 Census f o r each of t he se d i s t r i c t s . S i n c e the h o s p i t a l u t i l i z a t i o n da ta i n 1981/82 and 1982/83 were based on f i s c a l y e a r s , the m i d - p o i n t of the r e p o r t i n g p e r i o d was not the beg inn ing of June (Census Day) but the b e g i n n i n g of Oc tober . The p o p u l a t i o n f i g u r e s f o r 1981/82 were e x t r a p o l a t e d l i n e a r i l y f o u r months forward from the 1981 Census u s i n g p o p u l a t i o n f i g u r e s from both 1976 and 1981 Censuses . The 1982/83 p o p u l a t i o n f i g u r e s were d e r i v e d u s i n g the same method of e x t r a p o l a t i o n . Data f o r soc ioeconomic v a r i a b l e s were e x t r a c t e d from the 1971 and 1981 Census tapes a t the U n i v e r s i t y of B r i t i s h Co lumbia Data L i b r a r y , by Census Enumerat ion A r e a . A l l the Census tapes used i n t h i s s tudy were p r o v i d e d by S t a t i s t i c s Canada. 121 3 .4 .5 . H o s p i t a l bed c a p a c i t y d a t a H o s p i t a l Programs, B.C. M i n i s t r y of H e a l t h , m a i n t a i n s unpub l i s hed da ta on B.C. h o s p i t a l bed c a p a c i t y by t y p e . H o s p i t a l programs p r o v i d e d a l i s t of approved p a e d i a t r i c bed c a p a c i t y by h o s p i t a l f o r the year s 1966-1983/84 f o r t h i s s tudy . The bed count i n the l i s t r e p r e s e n t e d the s i t u a t i o n i n each h o s p i t a l a t the end of the y e a r (at the end of f i s c a l y e a r i n 1981/82-1982/83) . I f c a p a c i t y changes had taken p l a c e d u r i n g the y e a r , the y e a r - e n d f i g u r e s were a d j u s t e d u s i n g the exac t da tes of changes. These dates were a v a i l a b l e a t H o s p i t a l Programs. In the cases where o n l y month o r y e a r of change were known, m i d - p o i n t s were u sed . A f t e r these adjustments the bed c a p a c i t y da t a r e f l e c t e d average c a p a c i t y d u r i n g the y e a r , r a t h e r than y e a r end. These a d j u s t e d bed c a p a c i t y f i g u r e s were used t o c o n s t r u c t the p a e d i a t r i c bed a v a i l a b i l i t y v a r i a b l e ( s y n t h e t i c bed c o u n t ) . H o s p i t a l bed c a p a c i t y da ta was a l s o source f o r h o s p i t a l l o c a t i o n i n f o r m a t i o n used i n c o n s t r u c t i n g the o r i g i n - d e s t i n a t i o n m a t r i x e s . 3 .5 . S t a t i s t i c a l a n a l y s i s T h i s s tudy examines the r e l a t i o n s h i p s between day c a r e s u r g e r y a v a i l a b i l i t y , p a e d i a t r i c bed c a p a c i t y and p a e d i a t r i c i n p a t i e n t u t i l i z a t i o n w i t h s p e c i a l i n t e r e s t i n r e v e a l i n g c a u s a l a s s o c i a t i o n s . Fo r an a s s o c i a t i o n t o be c a u s a l i t shou ld have the expected tempora l r e l a t i o n s h i p between cause and 122 e f f e c t . Cause must precede e f f e c t . A l s o a change i n e x i s t e n c e o r magnitude o f c a u s a l f a c t o r shou ld l e a d t o a change i n the p u t a t i v e e f f e c t . Cause and e f f e c t must show a s t a t i s t i c a l a s s o c i a t i o n , and no o t h e r v a r i a b l e shou ld e x p l a i n t h i s a s s o c i a t i o n . C o n t r o l f o r o t h e r , p o s s i b l e con found ing , v a r i a b l e s i n r e v e a l i n g p o t e n t i a l c a u s a l e f f e c t s i s c r u c i a l i n t h i s s tudy . The a s s o c i a t i o n s between dependent and independent v a r i a b l e s i n t h i s s tudy were examined u s i n g the method o f l e a s t squares o r r e g r e s s i o n a n a l y s i s . In i t s s i m p l e s t form t h i s s t a t i s t i c a l p rocedure i s e q u i v a l e n t t o the p l o t t i n g dependent v a r i a b l e ( i n p a t i e n t u t i l i z a t i o n ) a g a i n s t an independent v a r i a b l e ( e . g . , day ca re s u r g e r y a v a i l a b i l i t y ) and f i t t i n g a l i n e through the s c a t t e r of p o i n t s p l o t t e d , i n such a way as t o m in im ize the sum, a c r o s s a l l o b s e r v a t i o n s , o f the squares of t h e i r v e r t i c a l d e v i a t i o n from the f i t t e d l i n e ( F i g u r e 2 ) . Each p o i n t p l o t t e d r e p r e s e n t s the observed da ta from a s i n g l e s c h o o l d i s t r i c t i n a s i n g l e y e a r . The da ta were f i r s t ana l yzed u s i n g s imp le r e g r e s s i o n , w i t h o n l y DCS e n t e r e d as an e x p l a n a t o r y v a r i a b l e . Then p o t e n t i a l con found ing v a r i a b l e s were e n t e r e d i n t o the r e g r e s s i o n model . A n a l y s e s were done u s i n g both i n d i v i d u a l y e a r da ta and the p o o l e d c r o s s - a r e a / c r o s s - y e a r d a t a s e t . The f o l l o w i n g parameters of the r e g r e s s i o n model a re p re sen ted i n the r e s u l t s of t h i s s t u d y : 123 DCS cases per 1000 population FIGURE 2. Hypothetical plot of inpatient use against DCS use. 124 P o i n t est:-i ma-he h of the r e g r e s s i o n c o e f f i c i e n t S r e f l e c t s the amount and d i r e c t i o n of change i n the dependent v a r i a b l e a s s o c i a t e d w i t h a one u n i t i n c r e a s e i n the v a l u e of the independent v a r i a b l e . I t i s an e s t i m a t e of the t r u e p o p u l a t i o n c o e f f i c i e n t , based on t h i s p a r t i c u l a r da ta sample. In F i g u r e 2 the c o e f f i c i e n t i s the s l o p e o f the r e g r e s s i o n l i n e o r the v a l u e b i n the r e g r e s s i o n equa t i on Y = a + bX. The r e g r e s s i o n c o e f f i c i e n t d e s c r i b e s the a s s o c i a t i o n between dependent and independent v a r i a b l e s . In the case o f m u l t i p l e r e g r e s s i o n the be ta c o e f f i c i e n t ( p a r t i a l c o e f f i c i e n t ) i s an e s t i m a t e of the a s s o c i a t i o n between the dependent v a r i a b l e and the independent v a r i a b l e when the e f f e c t s of a l l o t h e r v a r i a b l e s i n the e q u a t i o n a re h e l d c o n s t a n t . Va lues of - b c o e f f i c i e n t s a r e p r e s e n t e d i n t a b l e s under the names of independent v a r i a b l e s . S tandard e r r o r o f b (SE) d e s c r i b e s the amount of random e r r o r a s s o c i a t e d w i t h the c o e f f i c i e n t when the observed s c h o o l d i s t r i c t da ta a re v iewed as random drawings from some i n f i n i t e u n i v e r s e of s i m i l a r d i s t r i c t s and p o s s i b l e o b s e r v a t i o n s . Thus, the measured v a l u e of r e g r e s s i o n c o e f f i c i e n t i s i t s e l f an e s t i m a t e o f a t r u e but unknown v a l u e of t h i s parameter i n a l a r g e r u n i v e r s e . The degree of f a i t h to be p l a c e d i n t h i s e s t i m a t e of depends on i t s s i z e r e l a t i v e t o i t s own s tandard e r r o r . I f t h i s r a t i o ( t - r a t i o ) i s g r e a t e r than 1.99 when the r e g r e s s i o n c o e f f i c i e n t e s t ima te i s based on a t l e a s t 75 o b s e r v a t i o n s (as i n i n d i v i d u a l y e a r sample ) , o r g r e a t e r than 1.96 when the e s t i m a t e i s based on a t l e a s t 825 o b s e r v a t i o n s 125 (as i n p o o l e d c r o s s - d i s t r i c t / c r o s s - y e a r sample ) , then the random chance of o b t a i n i n g a c o e f f i c i e n t as l a r g e as what was o b s e r v e d , o r even l a r g e r , when the t r u e v a l u e ( i n the u n i v e r s e from which the observed da ta s e t i s a random sample) i s z e r o , i s l e s s than f i v e p e r c e n t . A r a t i o above 2.58 o r 2.65 , depending on the sample s i z e , i n d i c a t e s l e s s than one p e r c e n t chance. I n t e r c e p t (CONST) r e f e r s t o the p o i n t a t which the sample r e g r e s s i o n l i n e c r o s s e s the Y a x i s and r e p r e s e n t s the p r e d i c t e d v a l u e of the dependent v a r i a b l e when the v a l u e of the independent v a r i a b l e (or v a r i a b l e s ) i s zero ( F i g u r e 2 ) . The i n t e r c e p t i s the cons tan t a i n the r e g r e s s i o n e q u a t i o n Y = a + bX. I n t e r c e p t a i s a l s o a p o i n t e s t i m a t e , based on s tudy sample, o f the t r u e i n t e r c e p t a i n a l a r g e r u n i v e r s e . A d j u s t e d c o e f f i c i e n t o f d e t e r m i n a t i o n of the dependent v a r i a b l e around i t s mean ( ad ju s ted R 2 ) measures the e x t e n t t o which o v e r a l l v a r i a t i o n i n the dependent v a r i a b l e can be ' e x p l a i n e d by ' the r e g r e s s i o n model (or the v a r i a t i o n i n the independent v a r i a b l e s ) . I t d e s c r i b e s the goodness o f f i t of the r e g r e s s i o n e q u a t i o n . The adjustment of t h i s measure has c o r r e c t e d R 2 f o r degrees of f reedom. T h i s adjustment has r e l e v a n c e when t h e r e a re s e v e r a l independent v a r i a b l e s i n the e q u a t i o n a t the same t ime . Symbol R 2 i s used i n t h i s s tudy to r e f e r t o the a d j u s t e d c o e f f i c i e n t of d e t e r m i n a t i o n . 126 Standard prrnr o f pred i nt.fid valnfiB (SE Y) r e f l e c t s the p r e d i c t i v e r e l i a b i l i t y of the observed r e g r e s s i o n model a p p l i e d to s p e c i f i c o b s e r v a t i o n s . Knowing a , 6, and the v a l u e of the independent v a r i a b l e f o r a p a r t i c u l a r s c h o o l d i s t r i c t , one c o u l d ' p r e d i c t ' i t s v a l u e of the dependent v a r i a b l e from the r e g r e s s i o n e q u a t i o n . The SE Y would i n d i c a t e the degree of u n c e r t a i n t y a t t a c h e d t o t h a t p r e d i c t i o n . SE Y i n d i c a t e s the s t anda rd e r r o r of the p r e d i c t e d v a l u e s of the dependent v a r i a b l e , a r i s i n g out o f the f i t t e d r e l a t i o n , Y = a + bX. 127 4. RESULTS 4 . 1 . D e s c r i p t i v e d a t a - an ove rv iew o f p a e d i a t r i c u t i l i z a t i o n i n B .C . , 1968-1982/83 A l l the measures o f the dependent v a r i a b l e showed a g e n e r a l d e c l i n i n g t r e n d d u r i n g the s tudy p e r i o d (Tab le 9 ) , which i s independent o f any age-sex d i s t r i b u t i o n changes over t i m e . H o s p i t a l days showed a g r e a t e r dec rea se than a d m i s s i o n s , which means t h a t i n a d d i t i o n t o the d e c l i n e i n admi s s i on r a t e s i n the p a e d i a t r i c p o p u l a t i o n t h e r e was a l s o a dec rea se i n average l e n g t h o f s t a y . The g r e a t e s t dec rea se i n mean v a l u e s o f s c h o o l d i s t r i c t h o s p i t a l u t i l i z a t i o n r a t e s o c c u r r e d w i t h day c a r e s u r g e r y - t y p e i n p a t i e n t u t i l i z a t i o n (measures SURG A and SURG B ) . S u r p r i s i n g l y , the s u r g i c a l i n p a t i e n t u t i l i z a t i o n t h a t shou ld most c l o s e l y resemble day ca re su r ge ry u t i l i z a t i o n (SURG C) showed r e l a t i v e l y l i t t l e d e c l i n e . Dur ing the p e r i o d from 1968 t o 1976 the mean of t h i s v a r i a b l e showed no change i n r e s p e c t t o admiss ions and o n l y a s l i g h t dec rea se i n r e s p e c t t o h o s p i t a l days . However, t h e r e was a major drop i n t h i s t ype of u t i l i z a t i o n from 1976 t o 1981/82 (30 p e r c e n t dec rease i n admi s s i ons ) which was c l e a r l y l a r g e r than the dec rea se d u r i n g the p r e c e d i n g f i v e year s ( on l y 13 p e r c e n t dec rea se i n a d m i s s i o n s ) . T h i s drop i s not l i k e l y caused by c o i n c i d i n g s h i f t i n p rocedure and d i a g n o s i s cod ing (which took p l a c e i n 1979), because a s i m i l a r p a t t e r n of d e c l i n e over the s tudy Table 9 Means and Standard Dev ia t i ons o f D i f f e r e n t Measures of P a e d i a t r i c Inpat ien t U t i l i z a t i o n (Per 1,000 Popu la t ion) Over School D i s t r i c t s by Year MED/SURG SURG SURG-T&A SURG A SURG B SURG C Year Mean SD Mean SD Mean SD Mean SD Mean SD Mean SD ADMISSIONS: 1968 158.00 63.65 61.19 14.89 34.42 9.06 45.43 12.95 38.69 11.96 7.15 2.46 1969 152.44 63.91 52.10 13.18 31.64 8.18 37.17 10.83 31.90 9.74 7.68 2.81 1970 151.73 68.50 52.00 12.30 30.44 6.83 37.47 10.38 32.57 9.78 7.50 2.69 1971 150.02 63.52 49.15 9.44 30.74 6.81 34.82 8.71 30.48 8.25 8.28 2.88 1972 152.58 65.86 46.32 10.79 29.72 6.22 32.32 9.34 28.19 9.02 7.87 2.71 1973 145.09 65.78 44.65 11.61 29.95 6.38 29.92 9.92 26.20 9.76 8.24 3.07 1974 141.20 56.50 43.10 9.52 29.07 5.66 28.46 7.63 24.62 7.24 7.68 2.53 1975 130.80 52.13 40.30 9.37 28.19 6.50 26.19 7.79 22.60 7.19 7.61 3.02 1976 126.80 52.37 37.39 8.57 26.78 5.47 23.60 7.09 20.82 6.78 7.21 2.31 % Change between -19.75 -38.90 -22.20 -48.05 -46.19 0.84 1968-1976 1981 103.69 41.74 32.20 7.76 25.01 5.98 16.11 5.33 14.79 4.99 5.05 2.36 1982 95.11 42.44 28.53 8.46 22.88 7.27 13.56 5.45 12.56 4.97 4.52 2.42 % Change between -39.80 -53.38 -33.53 -70.15 -67.54 -36.78 1968-1982/83 Pooled 137.04 61.55 44.27 13.98 28.99 7.45 29.55 12.67 25.77 11.20 7.16 2.90 1968-1982/83 . C o n t i n u e d Table 9 Means and Standard Deviations of Different Measures of Paediatric Inpatient Utilization (Per 1,000 Population) Over School Districts by Year MED/SURG SURG SURG-T&A SURG A SURG B SURG C Year Mean SD Mean SD Mean SD Mean SD Mean SD Mean SD DAYS: 1968 1969 1970 1971 1972 1973 1974 1975 1976 % Change between 1968-1976 1981 1982 1968-1982/83 Pooled 1968-1982/83 1,044.46 510.66 323.30 79.68 258.90 70.32 151.74 48.27 84.83 26.77 17.42 6.12 1.019.65 538.69 278.26 73.05 231.43 67.56 121.78 43.64 71.22 23.99 18.48 7.63 987.76 563.07 262.70 78.84 212.80 70.36 119.10 38.83 72.07 22.60 17.72 6.61 941.67 498.47 246.30 66.97 205.74 66.68 107.57 29.77 65.76 17.80 18.68 6.30 934.33 505.50 235.18 69.88 199.27 64.13 100.08 34.62 59.85 17.73 17.16 5.55 834.64 444.65 222.32 72.66 190.41 66.64 92.27 41.06 55.59 19.93 18.07 6.26 802.64 424.14 218.79 72.21 187.98 70.71 89.28 33.91 53.38 15.94 17.19 5.71 732.67 366.95 199.75 53.15 173.19 49.00 80.28 29.41 48.44 15.95 16.50 6.99 693.58 381.63 182.75 47.89 159.60 45.79 68.98 25.18 44.43 15.19 15.57 5.08 -33.59 -43.47 -38.35 -54.54 -47.62 -10.62 470.97 200.01 144.00 43.87 128.99 42.46 38.70 15.30 28.90 9.72 10.15 4.63 431.39 200.86 135.05 53.46 123.41 52.58 32.21 16.47 24.08 10.57 9.10 5.04 -58.70 -58.23 -52.33 -78.77 -71.61 -47.76 802.52 479.30 222.58 84.56 188.34 72.47 91.09 47.78 55.32 25.43 16.00 6.78 130 p e r i o d was not a s s o c i a t e d w i th SURG A and SURG B measures, a l though they were a l s o based on the most common day c a r e s u r g e r y p rocedures and d i a g n o s i s , d e r i v e d from the 1982/83 da ta and t r a n s l a t e d to the 8th and 7th r e v i s i o n of ICD. With the se two measures, the d e c l i n e seems t o f o l l o w a s teady p a t t e r n over the whole s tudy p e r i o d . The drop i n SURG A and SURG B admis s ions was 32 p e r c e n t d u r i n g the f i v e y e a r p e r i o d from 1971 t o 1976, and 32 and 29 p e r c e n t , r e s p e c t i v e l y , d u r i n g the f o l l o w i n g f i v e y e a r s . I t i s g e n e r a l l y known t h a t much of the d e c l i n e i n p a e d i a t r i c h o s p i t a l u t i l i z a t i o n was caused by a d e c l i n e i n the t o n s i l l e c t o m y r a t e . A c c o r d i n g t o the da ta i n T a b l e 9, a p p r o x i m a t e l y 65 p e r c e n t of the d e c l i n e i n p e r c a p i t a s u r g i c a l admi s s ions over the s tudy p e r i o d was due t o the d e c l i n e i n the T&A r a t e . Both the SURG A and SURG B measure c o n t a i n e d t o n s i l l e c t o m i e s w i t h adeno idectomies but not t o n s i l l e c t o m i e s w i thou t adeno idec tomies . The o n l y two measures of the dependent v a r i a b l e t h a t d i d not i n c l u d e t o n s i l l e c t o m i e s a t a l l , SURG C and SURG-T&A, showed the lowest d e c l i n e of a l l s u r g i c a l measures. Between the f i v e y e a r p e r i o d from 1971 to 1976, both showed a 13 p e r c e n t d e c l i n e i n admi s s i on s . SURG C u t i l i z a t i o n p l a y e d o n l y a minor r o l e i n the o v e r a l l drop i n s u r g i c a l u t i l i z a t i o n . SURG C admiss ions r e p r e s e n t e d o n l y 16 p e r c e n t of the t o t a l s u r g i c a l admiss ions i n the poo led c r o s s -d i s t r i c t / c r o s s - y e a r sample w h i l e SURG A admis s ions r e p r e s e n t e d 67 p e r c e n t and SURG B 58 p e r c e n t . 131 The p e c u l i a r t ime t r e n d f o r the SURG C measure may be due to s h i f t s i n m e d i c a l p r a c t i c e over t ime . The SURG C v a r i a b l e was based on day ca re su r ge ry e l i g i b i l i t y as judged by a group of e x p e r t s i n 1983. I f an o p e r a t i v e p rocedure was c o n s i d e r e d s u i t a b l e f o r day ca re su r ge ry i n 1981 but not i n 1968 o r 1976, and i f s u b s t i t u t i o n f o r day c a r e s u r g e r y - t y p e i n p a t i e n t c a re r e a l l y o c c u r s , one would expect t o see a dec rea se i n SURG C u t i l i z a t i o n o n l y when m e d i c a l t h i n k i n g changes i n r e s p e c t t o day c a r e s u r g e r y s u i t a b i l i t y . The age- sex a d j u s t e d p a e d i a t r i c i n p a t i e n t u t i l i z a t i o n showed a h i g h v a r i a t i o n ac ro s s s c h o o l d i s t r i c t s . The r a t i o of h i g h e s t t o lowest admi s s ion r a t e between s c h o o l d i s t r i c t s v a r i e d from 5.1 i n 1975 to 7.7 i n 1973. C o e f f i c i e n t s o f v a r i a t i o n f o r each s tudy yea r d i d not show any c l e a r p a t t e r n of d i v e r g i n g o r converg ing of i n t e r - d i s t r i c t v a r i a t i o n over t i m e . The c o e f f i c i e n t s were h i g h e r f o r m e d i c a l / s u r g i c a l days than f o r admis s ions (averages were around 51 p e r c e n t and 42 p e r c e n t , r e s p e c t i v e l y ) . S u r g i c a l u t i l i z a t i o n r a t e s showed l e s s marked i n t e r - a r e a v a r i a t i o n than the t o t a l p a e d i a t r i c u t i l i z a t i o n . The h i g h e s t t o lowest r a t i o f o r s u r g i c a l admi s s i ons v a r i e d from 2.4 i n 1971 t o 4.8 i n 1982/83. The c o e f f i c i e n t of v a r i a t i o n was q u i t e s t a b l e from y e a r t o y e a r (around 24 p e r c e n t f o r admiss ions and 29 p e r c e n t f o r h o s p i t a l d a y s ) , except an i n c r e a s e , e s p e c i a l l y f o r h o s p i t a l day s , i n 1982/83. S i m i l a r i n c r e a s e i n i n t e r - d i s t r i c t v a r i a t i o n i n 1982/83 was a l s o found w i t h a l l o t h e r measures of s u r g i c a l 132 u t i l i z a t i o n . In g e n e r a l , of the d i f f e r e n t s u b c a t e g o r i e s of s u r g i c a l u t i l i z a t i o n , SURG-T&A showed the lowest c o e f f i c i e n t of v a r i a t i o n i n d i f f e r e n t s tudy y e a r s . The main independent v a r i a b l e , day c a r e s u r g e r y u t i l i z a t i o n , showed a marked i n c r e a s e d u r i n g the s tudy p e r i o d (Tab le 10) . Dur ing the f i v e y e a r p e r i o d from 1971 t o 1976 the mean r a t e over the s c h o o l d i s t r i c t s i n c r e a s e d 21 p e r c e n t and d u r i n g the subsequent f i v e yea r s the i n c r e a s e was 45 p e r c e n t . V a r i a t i o n o f day c a r e su r ge ry u t i l i z a t i o n a c r o s s s c h o o l d i s t r i c t s was much h i g h e r than w i t h i n p a t i e n t s u r g e r y . In 1968, 1969 and 197 3 t h e r e was a s c h o o l d i s t r i c t whose p o p u l a t i o n d i d not r e c e i v e p a e d i a t r i c day ca re su r ge ry a t a l l , w h i l e some s c h o o l d i s t r i c t s had 19 t o 37 day ca re su r ge ry cases pe r 1,000 p o p u l a t i o n o f 0-14 y e a r s . Dur ing the l a s t two s tudy y e a r s , when day c a r e su r ge ry had e s t a b l i s h e d i t s p re sence i n the p a e d i a t r i c p o p u l a t i o n i n a l l s c h o o l d i s t r i c t s , the h i g h e s t t o lowest r a t i o of day ca re su r ge ry was 9.5. The c o e f f i c i e n t s of v a r i a t i o n f o r each s tudy yea r showed a s teady dec rea se (from 102.1 t o 36.4 p e r c e n t ) i n i n t e r - d i s t r i c t v a r i a t i o n of p a e d i a t r i c day ca re su r ge ry use between 1968 and 1982/83. The p a e d i a t r i c bed a v a i l a b i l i t y measure showed a s l i g h t i n c r e a s e u n t i l the y e a r 1975, when i t s t a r t e d t o d e c l i n e (Tab le 10) . The f a l l i n mean v a l u e of t h i s v a r i a b l e was 25 p e r c e n t from 1975 to 1982/83, r e f l e c t i n g a g e n e r a l p o l i c y change toward bed r e d u c t i o n . A l though some s c h o o l d i s t r i c t s 133 T a b l e 1 0 Means and S tandard D e v i a t i o n s o f DCS and BEDS V a r i a b l e s (per 1 , 0 0 0 P o p u l a t i o n ) o v e r S choo l D i s t r i c t s by Year Year DCS BEDS Mean SD Mean SD 1968 1969 1970 1971 1972 1973 1974 1975 1976 % Change between 1968-76 1981/82 1982/83 % Change between 1968-82/83 Poo l ed 1968-82/83 4.27 6.38 9.44 11.35 11.64 12.86 13.06 13.57 13.69 220.61 19.85 19.83 364.40 12.36 4.36 6.13 7.53 8.22 6.76 7.47 7.13 7.03 7.06 7.28 7.22 8.30 3.17 3.34 3.38 3.64 3.64 3.58 3.57 3.59 3.55 11.99 2.97 2.70 -14.83 3.37 1.47 1.60 1.67 1.94 2.06 1.88 1.81 1.82 1.80 1.73 1.50 1.78 134 d i d not have t h e i r own p a e d i a t r i c beds a t a l l d u r i n g the s tudy p e r i o d , a l l u t i l i z e d p a e d i a t r i c beds i n o t h e r s c h o o l d i s t r i c t s . The h i g h e s t t o lowest r a t i o of the s y n t h e t i c , p o p u l a t i o n a d j u s t e d BEDS v a r i a b l e was around 10 from y e a r to y e a r . However, c o e f f i c i e n t s of v a r i a t i o n f o r each y e a r showed a s t eady i n c r e a s e i n i n t e r - d i s t r i c t v a r i a t i o n o f p a e d i a t r i c bed a v a i l a b i l i t y from 1968 t o 1972 (from 46.4 t o 56.6 p e r c e n t ) . In 1973 the v a r i a t i o n dec reased s l i g h t l y and l e v e l e d o f f i n 1974. In 1974-1976 the c o e f f i c i e n t o f v a r i a t i o n was 50.7 p e r c e n t . The two more r e c e n t yea r s i n the s tudy showed i n c r e a s e d i n t e r - d i s t r i c t v a r i a t i o n i n p a e d i a t r i c bed a v a i l a b i l i t y ( the c o e f f i c i e n t o f v a r i a t i o n was 58.2 p e r c e n t i n 1981/82 and 55.6 p e r c e n t i n 1982/83). P h y s i c i a n supp l y i n c r e a s e d d r a m a t i c a l l y d u r i n g the s tudy p e r i o d (Tab le 11) . The y e a r 1973, however, shows a c l e a r d e v i a t i o n from t h i s t r e n d i n r e s p e c t t o DOCS and OTHER (and, t o some ex tend , t o ANA). The DOCS and OTHER v a r i a b l e i n 1973 r e f l e c t the f a i l u r e of t h i s s tudy t o c a l c u l a t e FTE v a l u e s f o r p h y s i c i a n s whose s p e c i a l t y was unknown. These p h y s i c i a n s were a s s i g n e d a FTE v a l u e of one and a l l o c a t e d t o OTHER s p e c i a l t y . A c c o r d i n g t o T a b l e 11 t h i s p rocedure has o b v i o u s l y l e d to an o v e r e s t i m a t i o n of FTE v a l u e f o r p h y s i c i a n s w i t h unknown s p e c i a l t y . However, t h i s has not caused so much b i a s i n the l a t t e r y e a r s , because of improved i n f o r m a t i o n i n p h y s i c i a n s ' b i l l i n g d a t a . The p e c u l i a r t r e n d w i t h ANA i n T a b l e 11 may r e f l e c t a c e n t r a l i z a t i o n of a n a e s t h e s i o l o g i s t s t o fewer and Table 11 Means and Standard Deviations of Different Measures of Physician Availability per 10,000 Population (0-14 Years) Over School Districts by Year DOCS GP PAED SURGEON ANA OTHER Year Mean SD Mean SD Mean SD Mean SD Mean SD Mean SD 1973 44.70 10.78 24.45 6.39 0.81 0.66 7.60 3.71 0.59 1.80 11.24 8.93 1974 40.24 10.89 26.05 6.83 0.96 0.65 8.58 3.86 6.47 1.55 4.17 3.12 1975 41.15 9.97 26.99 7.52 1.10 0.91 8.39 3.62 0.23 0.60 4.44 3.48 1976 42.99 10.87 26.68 8.11 1.19 0.90 8.47 3.31 0.22 0.50 6.43 6.07 % Change between -3.83 9.12 46.91 11.45 -62.71 -42.79 1973-1976 1981 53.62 14.86 31.66 8.65 1.48 0.84 10.02 3.19 0.70 1.96 9.77 9.98 1982 54.67 18.16 32.59 10.16 1.49 1.17 10.60 5.99 0.64 1.60 9.36 11.12 h Change between 22.30 33.29 83.95 39.47 8.48 -16.73 1973-1982/83 Pooled 46.23 14.10 28.07 8.54 1.17 0.90 8.94 4.16 0.48 1.46 7.57 8.18 1973-1982/83 136 b i g g e r ( i n r e s p e c t t o p o p u l a t i o n ) d i s t r i c t s i n the 197 0s ( s i n c e these a re s c h o o l d i s t r i c t means). T h i s i n t e r p r e t a t i o n i s suppor ted by a s imul taneous dec rease i n the c o e f f i c i e n t of v a r i a t i o n o f the ANA v a r i a b l e . Of the d i f f e r e n t s p e c i a l t y c a t e g o r i e s , g e n e r a l and f a m i l y p r a c t i t i o n e r s (GP) formed the l a r g e s t group f o l l o w e d by s u r g i c a l s p e c i a l t i e s (SURGEON). However, the mean v a l u e of p a e d i a t r i c i a n s p e r p o p u l a t i o n ove r the s c h o o l d i s t r i c t s showed the h i g h e s t i n c r e a s e from 1973 t o 1982/83 (84 p e r c e n t i n c r e a s e ) , but t h e i r p r o p o r t i o n of a l l p h y s i c i a n s a v a i l a b l e to the p a e d i a t r i c p o p u l a t i o n remained q u i t e s m a l l ( l e s s than t h r e e p e r c e n t ) . Means of the soc ioeconomic v a r i a b l e s a c ro s s s c h o o l d i s t r i c t s d i d not change much from the 1971 Census t o 1981 Census (Tab le 12) . Tab le 13 shows the c o r r e l a t i o n m a t r i x o f the main s tudy v a r i a b l e s i n the poo led c r o s s - a r e a / c r o s s - y e a r d a t a . A c c o r d i n g t o s imp le c o r r e l a t i o n s , day ca re su r ge ry a v a i l a b i l i t y was n e g a t i v e l y r e l a t e d t o a l l measures of the dependent v a r i a b l e . However, the BEDS v a r i a b l e was n e g a t i v e l y c o r r e l a t e d w i t h DCS v a r i a b l e but p o s i t i v e l y w i t h the i n p a t i e n t u se , sugge s t i ng the p o s s i b i l i t y o f a s pu r i ou s r e l a t i o n s h i p between DCS and I n p a t i e n t use ( i . e . , BEDS i s a f f e c t i n g both of them). 137 T a b l e 12 Means and S tandard D e v i a t i o n s o f D i f f e r e n t Soc ioeconomic V a r i a b l e s Over S choo l D i s t r i c t s by Census Year V a r i a b l e 1971 Mean SD 1981 Mean SD CAN 81.33 4.59 80.98 5.74 MTENG 83.32 6.95 85.18 5.25 IND 4.94 6.56 4.56 6.57 RURAL 46.10 26.81 44.70 28.60 EDUC 1 4.67 2.78 15.21 4.71 ROOMS 5.14 0.38 5.75 0.38 INC 2 3,916.08 600.39 11/ 814.29 1 ,750.14 INC 3 9,839.39 1,508.51 11/ 814.29 1 ,750.14 UNEM 8.11 1.91 7.72 2.14 WHITE 45.01 9.67 40.06 10.11 PRIM 16.04 10.18 14.34 9.65 x> C l a s s i f i c a t i o n o f e d u c a t i o n was 1981; f i g u r e s a r e not comparable. d i f e r e n t i n 1971 and 2 ) 1971 incomes a r e not a d j u s t e d t o the 1981 l e v e l . 3> 1971 incomes a re a d j u s t e d t o the 1981 l e v e l u s i n g the Vancouver Consumer P r i c e Index. Table 13 Correlation Matrix of Main Study Variables in Pooled 1968-1982/83 Dataset MED/SURG SURG SURG-T&A SURG A SURG B SURG C DCS BEDS Admissions: MED/SURG 1.00 _ _ _ _ SURG 0.51 1.00 - - - - - -SURG-T&A 0.54 0.79 1.00 - - - - -SURG A 0.50 0.97 0.69 1.00 - - - -SURG B 0.42 0.96 0.64 0.98 1.00 - - -SURG C 0.25 0.58 0.70 0.57 0.59 1.00 - -DCS -0.25 -0.40 -0.27 -0.44 -0.40 -0.20 1.00 -BEDS 0.74 0.23 0.39 0.20 0.12 0.16 -0.20 1.00 Days: MED/SURG 1.00 _ _ _ _ _ SURG 0.67 1.00 - - - - - -SURG-T&A 0.66 0.97 1.00 - - - - -SURG A 0.64 0.83 0.73 1.00 - - - -SURG B 0.41 0.66 0.49 0.80 1.00 - - -SURG C 0.25 0.41 0.37 0.48 0.63 1.00 - -DCS -0.29 -0.38 -0.31 -0.46 -0.45 -0.26 1.00 -BEDS 0.75 0.43 0.47 0.35 0.16 0.22 -0.20 1.00 139 4.2 Day c a r e s u r g e r y a v a i l a b i l i t y and p a e d i a t r i c i n p a t i e n t u t i l i z a t i o n A r e g r e s s i o n a n a l y s i s of the MED/SURG and SURG u t i l i z a t i o n measures on day ca re su r ge ry a v a i l a b i l i t y was per formed f o r each s tudy y e a r . DCS d i d not have any s i g n i f i c a n t e f f e c t on t o t a l m e d i c a l / s u r g i c a l admiss ions u n t i l 1976, and the e f f e c t on s u r g i c a l admiss ions was s t a t i s t i c a l l y s i g n i f i c a n t o n l y i n 1981/82 and 1982/83 (Tab le 14) . In 1969, 1970, 1974 and 1975 the r e g r e s s i o n c o e f f i c i e n t on DCS was a l s o r e l a t i v e l y h i g h but so was a l s o i t s s t andard e r r o r , i n d i c a t i n g h i g h random f l u c t u a t i o n and u n c e r t a i n t y of the e s t i m a t e . I f h o s p i t a l ca re "need" was determined w h o l l y o u t s i d e the h o s p i t a l system, and i f the a v a i l a b i l i t y of day ca re su r ge ry i n a s c h o o l d i s t r i c t was u n c o r r e l a t e d e i t h e r w i t h need o r w i t h i n p a t i e n t c a p a c i t y l e v e l s , and i f a l l d i s t r i c t s had the same degree of s u r p l u s i n p a t i e n t and day ca re su r ge ry c a p a c i t y , then the s l o p e on DCS shou ld be -1 .00 and the assumption of c a u s a l r e l a t i o n s h i p between day c a r e s u r g e r y and i n p a t i e n t u t i l i z a t i o n shou ld h o l d . However, the r e s u l t s suggest t h a t t h i s s c e n a r i o i s much too s imp le to d e s c r i b e the r e a l i t y . F i r s t of a l l , day ca re s u r g e r y a v a i l a b i l i t y e x p l a i n s v e r y l i t t l e of the t o t a l v a r i a t i o n i n o v e r a l l m e d i c a l / s u r g i c a l and s u r g i c a l u t i l i z a t i o n ( l e s s than twe lve p e r c e n t , a t b e s t ) , which i n d i c a t e s t h a t t h e r e a re o t h e r f a c t o r s t h a t a re more impor tan t i n d e t e r m i n i n g the v a r i a t i o n o f p a e d i a t r i c h o s p i t a l u t i l i z a t i o n a c r o s s s c h o o l d i s t r i c t s . Second ly , the r e s u l t s i n 1976, 1981/82 and 1982/83 suggest t h a t 100 day ca re su r ge ry cases s u b s t i t u t e f o r Table 14 School District MED/SURG and SURG Equations with DCS by Year Admissions Days Measure & Year DCS SE CONST R2 SE Y OCS SE CONST R2 SE Y MEO/SURG: 1968 -0.28 1.71 159.19 -0.0133 64.07 -8.90 13.68 1.082.42 -0.0079 512.66 1969 -0.87 1.22 158.01 -0.0066 64.12 -10.40 10.22 1.085.94 0.0005 538.57 1970 -0.88 1.06 160.02 -0.0042 68.64 -2.08 8.75 1.007.39 -0.0129 566.69 1971 -0.13 0.90 151.44 -0.0134 63.94 -1.22 7.09 955.46 -0.0133 501.77 1972 0.28 1.14 149.38 -0.0129 66.28 -4.45 8.74 986.13 -0.0101 508.05 1973 -0.17 1.03 147.25 -0.0133 66.21 -4.53 6.95 892.90 -0.0078 446.39 1974 -1.20 0.92 156.85 0.0095 56.23 -9.51 6.87 936.74 0.0122 421.55 1975 -1.58 0.85 152.25 0.0324 51.28 -9.22 6.02 857.69 0.0179 363.65 1976 -1.881 0.84 152.46 0.0510 51.02 -12.811 6.15 868.93 0.0432 373.31 1981 -1.531 0.65 134.09 0.0586 40.50 -3.33 3.19 537.06 0.0012 199.90 1982 -1.591 0.66 126.57 0.0602 41.14 -3.83 3.22 507.29 0.0055 200.30 DAYS: 1968 0.01 0.40 61.16 -0.0100 14.99 -0.63 2.14 325.98 -0.0125 80.18 1969 -0.20 0.25 53.40 -0.0047 13.21 -1.11 1.39 285.33 -0.0049 73.23 1970 -0.21 0.19 53.98 0.0031 12.28 -0.11 1.23 263.74 -0.0136 79.37 1971 -0.26 0.13 52.09 0.0379 9.26 -0.41 0.95 250.90 -0.0112 67.34 1972 0.23 0.19 43.64 0.0074 10.75 0.45 1.21 229.98 -0.0118 70.29 1973 0.20 0.18 42.05 0.0034 11.59 -0.19 1.14 224.78 -0.0133 73.15 1974 -0.04 0.16 43.62 -0.0128 9.96 -0.89 1.18 230.37 -0.0059 72.42 1975 -0.11 0.16 41.81 -0.0066 9.40 -0.30 0.89 303.75 -0.0122 53.47 1976 -0.15 0.14 39.44 0.0017 8.57 -1.941 0.76 209.34 0.0693 46.20 1981 -0.322 0.12 38.62 0.0796 7.45 -0.72 0.70 158.36 0.0009 43.85 1982 -0.432 0.13 36.96 0.1197 7.94 -1.16 0.86 158.04 0.0112 53.17 1 p < 0.05 2 p < 0.01 141 a p p r o x i m a t e l y 150 m e d i c a l / s u r g i c a l i n p a t i e n t cases but o n l y 30-40 s u r g i c a l c a se s . Or, i n o t h e r words, 100 day c a r e s u r g e r y cases would s u b s t i t u t e f o r 110 m e d i c a l i n p a t i e n t c a s e s . T h i s , o f c o u r s e , i s nonsense and suggests t h a t something e l s e i s a f f e c t i n g the r e l a t i o n s h i p between DCS and i n p a t i e n t u t i l i z a t i o n . The r e s u l t s i n Tab le 14 a l s o show t h a t day c a r e s u r g e r y a v a i l a b i l i t y does not have any s i g n i f i c a n t e f f e c t on t o t a l m e d i c a l / s u r g i c a l o r s u r g i c a l p a t i e n t days when i n d i v i d u a l yea r s a r e concerned , w i t h the e x c e p t i o n o f the yea r 1976. Comparison of the admis s ion and h o s p i t a l day equa t i on s suggests t h a t the average l e n g t h of s t a y of the s u r g i c a l i n p a t i e n t s t h a t may have been s u b s t i t u t e d f o r by s u r g i c a l day c a r e would have been l e s s than t h r e e days i n 1981/82 and 1982/83 but n e a r l y 13 days i n 1976 which i s unreasonab le h i g h . The v a r i a t i o n i n m e d i c a l / s u r g i c a l cases e x p l a i n e d by the v a r i a t i o n i n s u r g i c a l day ca re use was p r a c t i c a l l y ze ro from 1968 t o 1974, and then i n c r e a s e d from t h r e e p e r c e n t t o s i x p e r c e n t between 1975 and 1982/83. Day ca re s u r g e r y use d i d not e x p l a i n v a r i a t i o n i n s u r g i c a l cases except i n 1971, 1981/82 and 1982/83. The goodness of f i t of the r e g r e s s i o n equa t i on s was a l s o v e r y poor f o r m e d i c a l / s u r g i c a l and s u r g i c a l days . The y e a r 1976 was the o n l y y e a r when DCS seemed t o e x p l a i n some of the v a r i a t i o n i n i n p a t i e n t days . The next s tep i n the a n a l y s i s was t o examine r e g r e s s i o n equa t i on s s e p a r a t e l y f o r each measure of the dependent 142 v a r i a b l e i n o r d e r t o see whether t h e r e i s any improvement i n p r e d i c t i o n when more r e s t r i c t e d s u r g i c a l c a t e g o r i e s a re s t u d i e d . R e s u l t s a re p re sen ted o n l y f o r 1971, 1976 and 1981/82, and f o r the poo led c r o s s - a r e a / c r o s s - y e a r da ta (Tab le 15) . The r e g r e s s i o n c o e f f i c i e n t on DCS i s s t a t i s t i c a l l y h i g h l y s i g n i f i c a n t w i th a l l measures of the dependent v a r i a b l e i n the poo led d a t a , but i n the i n d i v i d u a l yea r s the s i g n i f i c a n c e o f the c o e f f i c i e n t v a r i e s . T h i s i s p a r t l y due to a g r e a t e r number of o b s e r v a t i o n s i n the poo led da ta (825 s c h o o l d i s t r i c t s ) than i n the i n d i v i d u a l y e a r da t a (75 s c h o o l d i s t r i c t s ) . However, the r e g r e s s i o n c o e f f i c i e n t s a r e a l s o , i n g e n e r a l , h i g h e r and the e x p l a i n e d v a r i a n c e i s g r e a t e r i n the p o o l e d da ta compared to i n d i v i d u a l y e a r s , sugge s t i ng t h a t the c r o s s - a r e a / c r o s s - y e a r da ta cap tu re a l s o some k i n d of t i m e -dependent p roce s s t h a t a f f e c t s the r e l a t i o n s h i p between DCS and i n p a t i e n t u t i l i z a t i o n . The improvement of f i t ( ad ju s ted R 2 ) i s e s p e c i a l l y marked w i t h the equa t i ons f o r s u r g i c a l u t i l i z a t i o n measures which i n c l u d e T&As (SURG, SURG A, and SURG B) when moving from i n d i v i d u a l y e a r da ta t o poo led d a t a . T h i s suggests t h a t the cap tu red t i m e - e f f e c t might be s imp l y the dec rea se i n T&A r a t e s w i th the s imul taneous i n c r e a s e i n day c a r e s u r g e r y u t i l i z a t i o n . F i g u r e 3 t r i e s t o i l l u s t r a t e the d i f f e r e n c e i n r e g r e s s i o n equa t i ons i n i n d i v i d u a l y e a r da ta and p o o l e d c r o s s - d i s t r i c t / c r o s s - y e a r d a t a . There i s o n l y weak a s s o c i a t i o n between day ca re su r ge ry u t i l i z a t i o n and s u r g i c a l i n p a t i e n t u t i l i z a t i o n i n a c l u s t e r of o b s e r v a t i o n s of any i n d i v i d u a l y e a r . However, day c a r e su r ge ry u t i l i z a t i o n i s Tab le 15 School O i s t r i c t Inpat ient Hosp i t a l U t i l i z a t i o n Equat ions w i t h DCS in 1971, 1976, 1981/82 and Poo led 1968-1982/83 Dataset Admiss ions Days Year & Measure DCS SE CONST R 2 SE Y DCS SE CONST R 2 SE Y 1971 MEDS/SURG -0 .13 0.90 151.44 -0.0134 63.94 -1 .22 7.09 955.46 -0.0133 501.77 SURG - 0 . 2 6 1 0.13 52.09 0.0379 9.26 -0 .41 0.95 250.90 -0.0112 67.34 SURG-T&A -0 .07 0.10 31.54 -0.0065 6.83 0.12 0.95 204.35 -0.0135 67.13 SURG A - 0 . 3 1 1 0.12 38.34 0.0729 8.39 - 0 . 9 1 1 0.41 117.90 0.0503 29.01 SURG B - 0 . 2 7 1 0.11 33.53 0.0593 8.00 - 0 . 6 1 1 0.24 72.64 0.0658 17.20 SURG C -0 .05 0.04 8.87 0.0086 2.87 -0 .07 0.09 19.52 -0.0042 6.32 1976 MEDS/SURG - 1 . 8 8 1 0.84 152.46 0.0510 51.02 - 1 2 . 8 1 1 6.15 868.93 0.0432 373.31 SURG -0 .15 0.14 39.44 0.0017 8.57 - 1 . 9 4 1 0.76 209.34 0.0693 46.20 SURG-T&A -0 .07 0.09 27.76 -0.0051 5.48 - 1 . 5 3 1 0.74 180.55 0.0427 44.81 SURG A -0 .13 0.12 25.38 0.0032 7.08 -0 .67 0.41 78.16 0.0222 24.90 SURG B -0 .09 0.11 22.04 -0.0050 6.80 - 0 . 43 0.25 50.27 0.0261 14.99 SURG C -0 .01 0.04 7.40 -0.0120 2.32 -0 .07 0.08 16.57 -0.0034 5.09 1981/82 MEDS/SURG - 1 . 5 3 1 0.65 134.09 0.0586 40.50 - 3 . 33 3.19 537.06 0.0012 199.90 SURG - 0 . 3 2 2 0.12 38.62 0.0796 7.45 ' - 0 . 72 0.70 158.36 0.0009 43.85 SURG-T&A - 0 . 2 3 1 0.09 29.60 0.0668 5.78 -0 .43 0.68 137.46 -0.0083 42.64 SURG A - 0 . 2 0 1 0.08 20.09 0.0620 5.17 - 0 . 6 1 1 0.24 50.75 0.0707 14.75 SURG B - 0 . 1 7 1 0.08 18.08 0.0457 4.87 - 0 . 4 4 2 0.15 37.54 0.0938 9.26 SURG C -0 .07 0.04 6.50 0.0384 2.31 - 0 . 1 7 1 0.07 13.42 0.0539 4.51 Pooled MEDS/SURG - 1 . 8 3 3 0.25 159.70 0.0601 59.67 - 1 6 . 6 7 3 1.93 1014.50 0.0823 459.15 SURG - 0 . 6 7 3 0.05 52.49 0.1551 12.85 - 3 . 9 0 3 0.33 270.74 0.1454 78.17 SURG-T&A - 0 . 2 4 3 0.03 32.00 0.0727 7.17 - 2 . 7 2 3 0.29 221.94 0.0961 68.86 SURG A - 0 . 6 7 3 0.05 37.87 0.1934 11.37 - 2 . 6 2 3 0.18 123.40 0.2056 42.58 SURG B - 0 . 5 5 3 0.04 32.50 0.1624 10.25 - 1 . 3 8 3 0.10 72.31 0.2006 22.73 SURG C - 0 . 0 7 3 0.01 8.02 0.0383 2.85 - 0 . 2 1 3 0.03 18.58 0.0640 6.56 1 2 3 p < 0.05 p < 0.01 p < 0.001 c o 3 a. o o. o o o C L «/> <u l/l ca u • Observation in year 1 o Observation in year 2 T Observation in year 3 A Observation in year 4 + Observation in year 5 Regression line in pooled (years 1-5) dataset Regression line in individual year dataset c <v ro C L C DCS cases per 1000 population FIGURE 3- Simplified i l lustrat ion of the differences in regression equations between individual years and the pooled dataset. 145 i n c r e a s i n g over t ime w h i l e s u r g i c a l i n p a t i e n t u t i l i z a t i o n i s d e c r e a s i n g , and these two t rends a re p r o b a b l y l a r g e l y independent o f each o t h e r , s i n c e the dec rea se i n i n p a t i e n t u t i l i z a t i o n i s l a r g e l y caused by dec rease i n non-day c a r e s u r g e r y e l i g i b l e t o n s i l l e c t o m i e s . Thus a c l u s t e r of o b s e r v a t i o n s i n one yea r w i l l be , on the average , a t a lower l e v e l of i n p a t i e n t u t i l i z a t i o n and a t a h i g h e r l e v e l o f day c a r e s u r g e r y use than the c l u s t e r of o b s e r v a t i o n s i n the p r e v i o u s y e a r . When a r e g r e s s i o n e q u a t i o n i s f i t t e d t o the p o o l e d c r o s s - d i s t r i c t / c r o s s - y e a r d a t a , i t w i l l c a p t u r e t h i s t r e n d and show a h i g h r e g r e s s i o n c o e f f i c i e n t on DCS, a l though t h e r e i s no n e c e s s a r y c a u s a t i o n between DCS and s u r g i c a l i n p a t i e n t u t i l i z a t i o n . None of the d i f f e r e n t measures of s u r g i c a l admis s ions were a f f e c t e d by the day ca re su r ge ry a v a i l a b i l i t y i n 1976, but i n 1971 and 1981/82 DCS had a s t a t i s t i c a l l y s i g n i f i c a n t n e g a t i v e a s s o c i a t i o n , c a u s a l o r n o n - c a u s a l , w i t h SURG A and SURG B u t i l i z a t i o n . However, the a c t u a l c o e f f i c i e n t s were s t i l l q u i t e low, i m p l y i n g s u b s t i t u t i o n o f l e s s than one t h i r d . The e x p l a i n e d v a r i a t i o n was l e s s than e i g h t p e r c e n t w i t h admi s s ions and l e s s than 10 p e r c e n t w i t h h o s p i t a l days . The e f f e c t of DCS was l e s s on SURG-T&A admis s ions than on SURG A and SURG B i n 1971 but i n 1981/82 the e f f e c t s were a l l r o u g h l y the same magnitude and e q u a l l y s i g n i f i c a n t . These c r o s s - s e c t i o n a l r e s u l t s p r o b a b l y r e f l e c t h i g h e r T&A r a t e s i n 146 s c h o o l d i s t r i c t s w i t h l e s s DCS a c t i v i t y i n 1971, but not i n 1981/82. T h i s r a i s e s a p o s s i b i l i t y t h a t a low T&A r a t e and a h i g h DCS r a t e i n a s c h o o l d i s t r i c t were 'ma rke r s ' of ' m e d i c a l p r o g r e s s i v i t y ' i n t h a t d i s t r i c t i n the e a r l y 1970s. In 1971, ' p r o g r e s s i v e ' p h y s i c i a n s were p r o b a b l y the f i r s t t o reduce T&As and s t a r t pe r fo rm ing day ca re s u r g e r y . Ten yea r s l a t e r , both of t he se p r a c t i c e s had become commonplace. T h i s would be c o n s i s t e n t w i t h the f i n d i n g s i n Tab le 15. A low r e g r e s s i o n c o e f f i c i e n t on DCS and p a r t i c u l a r l y a low R 2 i n the e q u a t i o n f o r SURG C both i n i n d i v i d u a l y e a r da ta and i n the poo led da ta was a s u r p r i s e , a l though r e s u l t s i n T a b l e 9 a l r e a d y suggested t h a t day ca re su r ge ry may not have much e f f e c t on t h i s measure. A l though the v a r i a t i o n i n SURG C admi s s ions ' e x p l a i n e d by ' the v a r i a t i o n i n day ca re su r ge ry a v a i l a b i l i t y was h i g h e r i n 1981/82 than i n 1976 o r 1971, i t was s t i l l lower than the e x p l a i n e d v a r i a t i o n w i t h o t h e r measures of p a e d i a t r i c h o s p i t a l u se . R e s u l t s w i t h the poo led da ta i n T a b l e 15 w i t h r e s p e c t t o measures of s u r g i c a l i n p a t i e n t u t i l i z a t i o n show more o r l e s s what one would e x p e c t , w i t h the e x c e p t i o n o f the SURG C e q u a t i o n . More o f the v a r i a t i o n i n t o t a l s u r g i c a l use (around 15 p e r c e n t ) was accounted f o r by day ca re s u r g e r y a v a i l a b i l i t y than i n o v e r a l l m e d i c a l / s u r g i c a l use (6-8 p e r c e n t ) . Fu r the rmore , more of the v a r i a t i o n i n day c a r e s u r g e r y - t y p e of i n p a t i e n t use (SURG A) was e x p l a i n e d by v a r i a t i o n i n day ca re 147 s u r g e r y a v a i l a b i l i t y than i n t o t a l s u r g i c a l u se . But the r e g r e s s i o n c o e f f i c i e n t s w i t h the poo led da ta suggest t h a t day c a r e s u r g e r y a v a i l a b i l i t y " saves " more m e d i c a l than s u r g i c a l admis s ions and p a t i e n t days . The c o e f f i c i e n t s imp ly t h a t 100 c h i l d r e n ca red f o r i n a day ca re s u r g e r y u n i t would dec rea se the o v e r a l l s u r g i c a l admiss ions by 67. A compar i son of the equa t i on s f o r admiss ions and days i m p l i e s a l e n g t h of s t a y f o r the " saved " i n p a t i e n t su r ge ry cases of about 6 days , which i s w e l l above the average l e n g t h o f s t a y found i n the e a r l i e r r e s e a r c h (Evans and Rob inson, 1973). The next e q u a t i o n i m p l i e s t h a t 100 c h i l d r e n ope ra ted on i n a day c a r e s u r g e r y u n i t would save o n l y 24 "non-T&A" i n p a t i e n t a d m i s s i o n s , which i s a s u s p i c i o u s l y low number g i v e n the g e n e r a l f e e l i n g t h a t t o n s i l l e c t o m i e s a r e not s u i t a b l e f o r day c a r e s u r g e r y . A comparison of admi s s ion and h o s p i t a l day equa t i on s i m p l i e s t h a t the saved "non-T&A" s u r g i c a l admiss ions would have had an average l e n g t h o f s t a y of 11.3 days , which i s u n r e a l i s t i c a l l y h i g h . The p r o p o r t i o n of v a r i a t i o n i n i n p a t i e n t u t i l i z a t i o n t h a t was accounted f o r by the v a r i a t i o n i n day ca re s u r g e r y a v a i l a b i l i t y was h i g h e s t w i th SURG A i n the poo led d a t a . The r e g r e s s i o n c o e f f i c i e n t s imp ly t h a t a l l SURG " s a v i n g s " would be SURG A type (100 day ca re su r ge ry cases w i l l save 67 i n p a t i e n t admis s ions of SURG A type) and the average l e n g t h of s t a y of " s aved " cases would be 3.9 days , which i s r e a s o n a b l e . The 148 p l a u s i b i l i t y t h a t t h i s r e p r e s e n t s r e a l s u b s t i t u t i o n i s , however, l e s s e n e d by the l a c k of s i m i l a r s t r e n g t h i n the equa t i o n w i t h i n d i v i d u a l year d a t a . A t h i r d f a c t o r , a s h i f t i n s u r g i c a l p r a c t i c e over time, f o r example, may have i n f l u e n c e both on DCS use and SURG A type u t i l i z a t i o n and cause the observed c o r r e l a t i o n ( s t a t i s t i c a l l y s i g n i f i c a n t but not c a u s a l because of a m i s s i n g v a r i a b l e ) . The next equation (SURG B) does not i n c r e a s e the p l a u s i b i l i t y of c a u s a l a s s o c i a t i o n . When cases t h a t have lo n g e r l e n g t h of s t a y than f i v e days or do not have d i a g n o s i s / p r o c e d u r e combinations t h a t can be found among day care surgery p a t i e n t s are excluded, one would expect to see a t l e a s t the same k i n d of improvement i n the o v e r a l l goodness of f i t of the r e g r e s s i o n equation i f a s u b s t i t u t i o n model was t r u e . Instead, the a d j u s t e d R 2 i s a l i t t l e lower. The r e g r e s s i o n c o e f f i c i e n t f a l l s from -0.67 t o -0.55 i n r e s p e c t t o admissions when moving from the SURG A equ a t i o n t o the SURG B equ a t i o n . The average l e n g t h of s t a y of "saved" admissions i m p l i e d by the SURG B equations was 2.5 days. Given the unexplained f i n d i n g s w i t h these equations and a number of m i s s i n g v a r i a b l e s t h a t have not been accounted f o r , one i s l e d t o conclude t h a t the a s s o c i a t i o n between day care s u r g e r y and i n p a t i e n t use, which has been estimated a t t h i s stage, w h i l e s t a t i s t i c a l l y h i g h l y s i g n i f i c a n t i n the pooled d a t a , i s not a b a s i s f o r i n f e r r i n g c a u s a l i t y . The r e s u l t s p r esented so f a r do not exclude the p o s s i b i l i t y t h a t the r e l a t i o n s h i p between day care surgery and i n p a t i e n t use i s 149 a c t u a l l y go ing i n the o t h e r d i r e c t i o n , o r more p l a u s i b l y , t h a t both v a r i a b l e s might be i n f l u e n c e d j o i n t l y by some t h i r d f a c t o r o r f a c t o r s . 4.3 P a e d i a t r i c bed a v a i l a b i l i t y and i n p a t i e n t u t i l i z a t i o n The most obv ious v a r i a b l e to check f o r a con found ing i n f l u e n c e on the r e l a t i o n s h i p between s u r g i c a l day c a r e a v a i l a b i l i t y and p a e d i a t r i c i n p a t i e n t use i s , of c o u r s e , the a v a i l a b l e supp l y of p a e d i a t r i c beds. As the c o r r e l a t i o n m a t r i x i n T a b l e 13 showed, supp l y of beds i s n e g a t i v e l y c o r r e l a t e d w i t h day ca re su r ge ry a v a i l a b i l i t y , a l though the c o r r e l a t i o n i s s m a l l . More beds a r e a s s o c i a t e d w i t h somewhat l e s s day c a r e su r ge ry u t i l i z a t i o n . S i nce the bed c a p a c i t y , i n g e n e r a l , had been b u i l t b e f o r e the i n t r o d u c t i o n of day c a r e s u r g e r y , i t i s p l a u s i b l e t h a t the r e l a t i o n s h i p works from beds t o day c a r e s u r g e r y : day ca re su r ge ry i s i n t r o d u c e d i n a reas where t h e r e a r e few i n p a t i e n t beds. Roemer's Law suggests t h a t bed a v a i l a b i l i t y determines i n p a t i e n t u t i l i z a t i o n . The s imp le c o r r e l a t i o n between BEDS and MED/SURG i n T a b l e 13 was as h i gh as .74. I f p a e d i a t r i c bed a v a i l a b i l i t y i s c a u s a l l y r e l a t e d to i n p a t i e n t u t i l i z a t i o n and i f the bed supp ly a l s o determines the a v a i l a b i l i t y of day ca re s u r g e r y , then one would f i n d t h a t a h i g h l e v e l of day ca re su r ge ry a c t i v i t y i s a s s o c i a t e d w i t h a low l e v e l of i n p a t i e n t a c t i v i t y , but the a s s o c i a t i o n would not be c a u s a l . 150 Reg re s s i on s of t o t a l m e d i c a l / s u r g i c a l i n p a t i e n t u t i l i z a t i o n on bed a v a i l a b i l i t y showed a cons tan t p a t t e r n from one y e a r to ano ther (Tab le 16) . Bed a v a i l a b i l i t y had a v e r y s t r o n g r e l a t i o n s h i p to both i n p a t i e n t admiss ions and p a t i e n t days . The p r o p o r t i o n of v a r i a t i o n i n t o t a l m e d i c a l / s u r g i c a l admis s ions accounted f o r by p a e d i a t r i c bed a v a i l a b i l i t y v a r i e d from 45.8 p e r c e n t i n 1968 to 68.7 p e r c e n t i n 1976. The v a r i a t i o n i n h o s p i t a l days was e x p l a i n e d s l i g h t l y b e t t e r by the v a r i a t i o n i n bed a v a i l a b i l i t y than v a r i a t i o n i n a d m i s s i o n s . The compar ison of a d j u s t e d R 2 i m p l i e s t h a t i n 1968-1976 l e n g t h of s t a y was more s e n s i t i v e t o bed supp l y than admi s s ions but i n 1981/82-1982/83 the p a t t e r n o f h o s p i t a l i z a t i o n was not v e r y s e n s i t i v e t o bed a v a i l a b i l i t y once p a t i e n t s were h o s p i t a l i z e d . The goodness of f i t of the p a t i e n t day equa t i ons ranged from 55.2 p e r c e n t i n 1970 t o 80.1 p e r c e n t i n 1974. The s t r e n g t h of a s s o c i a t i o n between BEDS and i n p a t i e n t u t i l i z a t i o n showed a s l i g h t dec rease over t ime w i th r e s p e c t t o admis s ions but more marked f a l l w i t h r e s p e c t t o p a t i e n t days . E s p e c i a l l y a f t e r the y e a r 1976 the r e g r e s s i o n c o e f f i c i e n t on BEDS i n p a t i e n t day equa t i on s had f a l l e n a lmost i n t o h a l f of i t s l e v e l i n 1976. The r e s u l t s i n T a b l e 16 suggest t h a t i n 1968 one a d d i t i o n a l p a e d i a t r i c bed would have meant 29.6 a d d i t i o n a l admiss ions and 280.4 a d d i t i o n a l p a t i e n t days and i n 1982/83 21.4 a d d i t i o n a l admiss ions and 99.1 p a t i e n t days . These f i g u r e s imp ly an average l e n g t h of s t a y of 9.5 days i n 1968 and 4.6 days i n 1982/83 and an average 151 Table 16 School District MED/SURG and SURG Equations with BEDS by Year Admissions Days Measure & Year BEDS SE CONST R2 SE Y BEDS SE CONST R2 SE Y MED/SURG: • 1968 29.593 3.72 64.18 0.4575 46.88 280.433 24.15 155.13 0.6441 304.67 1969 30.143 3.07 51.76 0.5638 42.21 268.043 23.83 124.35 0.6292 328.05 1970 28.173 3.50 56.66 0.4627 50.21 252.253 26.30 136.51 0.5516 377.07 1971 25.963 2.33 55.46 0.6250 38.89 210.383 17.21 175.28 0.6674 287.46 1972 24.523 2.41 63.37 0.5817 42.59 206.313 15.60 183.79 0.7016 276.15 1973 25.533 2.81 53.81 0.5251 45.33 202.043 14.44 112.29 0.7247 233.32 1974 25.673 2.09 49.55 0.6703 32.44 210.343 12.15 51.56 0.8014 189.06 1975 23.303 1.95 47.15 0.6571 30.53 178.643 10.94 91.30 0.7821 171.30 1976 24.263 1.90 40.76 0.6874 29.28 182.183 12.81 47.34 0.7311 197.89 1981/82 19.953 1.59 44.47 0.6789 23.65 95.463 7.65 187.65 0.6766 113.74 1882/83 21.353 2.02 37.56 0.5986 26.89 99.053 9.86 164.38 0.5745 131.02 SURG: 1968 0.73 1.19 58.87 -0.0085 14.95 27.603 5.48 235.76 0.2481 69.09 1969 0.95 0.96 48.92 -0.0001 13.18 23.003 4.62 201.45 0.2436 63.53 1970 1.21 0.85 47.92 0.0134 12.22 17.983 5.12 202.03 0.1328 73.42 1971 0.58 0.57 47.03 0.0008 9.44 18.163 3.43 180.16 0.2673 57.32 1972 1.251 0.60 41.79 0.0436 10.55 19.333 3.27 164.86 0.3149 57.84 1973 0.81 0.72 41.77 0.0035 11.59 20.743 3.82 148.15 0.2778 61.75 1974 1.572 0.59 37.50 0.0761 9.15 24.033 3.73 132.98 0.3534 58.06 1975 2.493 0.53 31.36 0.2236 8.26 17.673 2.72 136.33 0.3573 42.61 1976 1.772 0.52 31.10 0.1258 8.02 13.093 2.72 136.34 0.2303 42.01 1981/82 1982/83 2.42° 3.123 0.44 0.53 25.02 20.13 0.2801 0.3147 6.59 7.01 12.71° 16.143 2.57 3.58 106.27 91.56 0.2408 0.2066 38.22 47.62 1 p < 0.05 2 p < 0.01 3 p < 0.001 152 occupancy r a t e of an a d d i t i o n a l bed of 77 p e r c e n t and 27 p e r c e n t r e s p e c t i v e l y . P a e d i a t r i c bed a v a i l a b i l i t y was l e s s s t r o n g l y r e l a t e d to s u r g i c a l i n p a t i e n t use, and the p r o p o r t i o n of v a r i a t i o n e x p l a i n e d by the v a r i a t i o n i n bed supply was l e s s than f o r the t o t a l m e d i c a l / s u r g i c a l use (the h i g h e s t a d j u s t e d R 2 w i t h admissions was 31.5 percent and w i t h p a t i e n t days 35.7 p e r c e n t ) . Comparison of equations f o r admissions and p a t i e n t days suggested t h a t a l s o i n s u r gery l e n g t h of s t a y i s more s e n s i t i v e t o bed a v a i l a b i l i t y than admission r a t e except i n 1981/82-1982/83. Comparison of r e g r e s s i o n c o e f f i c i e n t s from one year t o another showed s l i g h t l y s t r e n g t h e n i n g a s s o c i a t i o n between bed supply and s u r g i c a l admissions but d e c r e a s i n g a s s o c i a t i o n between bed supply and s u r g i c a l days over time. I t i s i n t e r e s t i n g t o note t h a t the a s s o c i a t i o n between BEDS and s u r g i c a l admissions became s t r o n g e r and the f i t of the e q u a t i o n improved a t the same time when the p a e d i a t r i c bed c a p a c i t y i n the p r o v i n c e s t a r t e d t o d e c l i n e . The r e s u l t s i n T a b l e 16 suggest t h a t one a d d i t i o n a l p a e d i a t r i c bed would have meant o n l y 0.7 a d d i t i o n a l s u r g i c a l admissions and 27.6 a d d i t i o n a l s u r g i c a l days i n 1968. In 1982/83 these same f i g u r e s would have been 3.1 and 16.1, r e s p e c t i v e l y . In 1971, bed a v a i l a b i l i t y showed the s t r o n g e s t a s s o c i a t i o n w i t h SURG-T&A of a l l the s u r g i c a l u t i l i z a t i o n measures whereas the SURG measure showed the s t r o n g e s t r e l a t i o n s h i p i n 1976 and 153 1981/82 (Tab le 17) . The a s s o c i a t i o n between bed a v a i l a b i l i t y and SURG A, SURG B and SURG C admis s ions were weak and s t a t i s t i c a l l y i n s i g n i f i c a n t i n 1971. In 1976 and 1981/82 these measures showed s t r o n g e r a s s o c i a t i o n , and i n 1981/82 bed a v a i l a b i l i t y had s t a t i s t i c a l l y s i g n i f i c a n t r e l a t i o n s h i p t o a l l measures of p a e d i a t r i c i n p a t i e n t u t i l i z a t i o n . The goodness of f i t of the r e g r e s s i o n equa t i on f o r d i f f e r e n t s u r g i c a l admi s s i on measures was h i g h e s t w i th SURG-T&A i n 1981/82 (35.4 p e r c e n t ) and f o r d i f f e r e n t s u r g i c a l day measures w i t h SURG A a l s o i n 1981/82 (38.5 p e r c e n t ) . With the poo led da ta the be ta c o e f f i c i e n t on BEDS was s t a t i s t i c a l l y h i g h l y s i g n i f i c a n t i n a l l e q u a t i o n s , but the s t r e n g t h of the a s s o c i a t i o n s d i d not d i f f e r much from those i n 1976 and 1981/82. The e x p l a i n e d v a r i a t i o n was f a i r l y low i n the SURG A, B and C e q u a t i o n s . The be ta c o e f f i c i e n t on p a e d i a t r i c bed supp l y was a lmost the same f o r t o t a l m e d i c a l / s u r g i c a l u t i l i z a t i o n i n the poo led da ta as i n the i n d i v i d u a l y e a r d a t a , but the a d j u s t e d R 2 was l e s s i n the poo led s e t than i n i n d i v i d u a l y e a r s . The s t a b i l i t y of the be ta c o e f f i c i e n t on p a e d i a t r i c bed a v a i l a b i l i t y i n the r e g r e s s i o n equa t i on f o r t o t a l m e d i c a l / s u r g i c a l admi s s i on s , and the h i gh p r o p o r t i o n of the v a r i a t i o n accounted f o r by the BEDS v a r i a b l e suppor t s the h y p o t h e s i s t h a t bed supp l y i n c r e a s e s i n p a t i e n t u t i l i z a t i o n , but the ev i dence o f the c a u s a l i t y i s not c o n c l u s i v e . A c c o r d i n g t o the equa t i ons w i t h poo led da ta one a d d i t i o n a l p a e d i a t r i c be w i l l g i v e r i s e t o about 26 a d d i t i o n a l Table 17 School District inpatient Hospital Utilization Equations with BEDS in 1971. 1976. 1981/82 and Pooled 1968-1982/83 Dataset Admissions Days Year & Measure BEDS SE CONST R2 SE Y BEDS SE CONST R2 SE Y 1971 MED/SURG SURG SURG-T&A SURG A SURG B SURG C 1976 MED/SURG SURG SURG-T&A SURG A SURG B SURG C 25.96° 0.58 1.753 0.28 -0.35 0.08 24.26° 1.7/2 l . l l 2 1.452 1.001 0.27 2.33 0.57 0.36 0.52 0.50 0.17 1.90 0.52 0.33 0.43 0.43 0.15 55.46 47.03 24.36 33.82 31.75 7.99 40.76 31.10 22.86 18.45 17.28 6.25 0.6250 0.0008 0.2393 -0.0099 -0.0068 -0.0108 0.6874 0.1258 0.1199 0.1234 0.0571 0.0320 38.89 9.44 5.94 8.76 8.28 2.90 29.28 8.02 5.13 6.64 6.58 2.27 210.38° 18.163 19.383 5.513 -0.11 0.41 182.183 13.093 11.173 7.593 2.722 0.892 17.21 3.43 3.32 1.67 1.07 12.81 2.72 2.68 1.38 0.94 0.31 175.29 180.16 135.16 87.52 66.17 0.6674 0.2673 0.3092 0.1171 -0.0135 0.38 17.19 0.0024 47.34 136.34 119.99 42.07 34.79 12.40 0.7311 0.2303 0.1807 0.2831 0.0910 0.0873 287.46 57.32 55.43 27.97 17.92 6.30 197.89 42.01 41.45 21.32 14.49 4.86 1981/82 MED/SURG 19.95° 1.59 44.47 0.6789 23.65 SURG 2.423 0.44 25.02 0.2801 6.59 SURG-T&A 2.083 0.32 18.82 0.3541 4.81 SURG A 1.223 0.33 12.50 0.1444 4.93 SURG B 0.791 0.33 12.44 0.0628 4.83 SURG C 0.432 0.15 3.78 0.0855 2.26 Pooled MED/SURG 25.743 0.81 50.20 0.5521 41.19 SURG 1.793 0.27 38.21 0.0509 13.62 SURG-T&A 1.653 0.13 23.41 0.1544 6.85 SURG A 1.413 0.24 24.80 0.0378 12.42 SURG B 0.763 0.22 23.19 0.0135 11.12 SURG C 0.273 0.06 6.26 0.0257 2.87 1 p < 0.05 2 p < 0.01 3 D < 0.001 95.46° 12.713 11.993 5.553 1.581 0.832 202.903 20.313 18.973 9.273 2.313 0.823 7.65 187.65 0.6766 113.74 2.57 2.51 0.81 0.63 0.30 6.19 1.50 1.26 0.88 0.49 0.13 106.27 93.41 22.23 24.22 7.69 123.94 154.07 124.33 59.81 47.53 13.23 0.2408 0.2279 0.3852 0.0662 0.0834 0.5658 0.1813 0.2159 0.1180 0.0249 0.0453 38.22 37.31 12.00 9.40 4.44 315.84 76.51 64.13 44.87 25.11 6.63 155 admis s ions (20-30 admiss ions a c c o r d i n g to the equa t i on s i n i n d i v i d u a l y e a r s ) and t o about 203 a d d i t i o n a l p a t i e n t days (96-280 days a c c o r d i n g to the i n d i v i d u a l y e a r d a t a ) . T h i s i m p l i e s an average l e n g t h of s t a y of 7.8 f o r each a d d i t i o n a l admi s s i on and an average occupancy r a t e o f 56 p e r c e n t f o r the a d d i t i o n a l bed (203/365). The occupancy r a t e c a l c u l a t e d from the d e s c r i p t i v e da ta i n Tab le 9 and 10 was o n l y s l i g h t l y h i g h e r , 66 p e r c e n t . In o t h e r words, an a d d i t i o n a l bed would be o n l y 17 p e r c e n t l e s s o ccup ied than e x i s t i n g beds , a l though the l e v e l of occupancy i s , i n g e n e r a l , q u i t e low. The second e q u a t i o n i n the poo led da ta i m p l i e s t h a t out of the 26 a d d i t i o n a l admiss ions t r i g g e r e d by an a d d i t i o n a l bed l e s s than two would be s u r g i c a l admiss ions (Tab le 17) . S i nce the e s t i m a t e d i n c r e a s e i n s u r g i c a l admiss ions due t o an i n c r e a s e i n beds i s o n l y about 7 p e r c e n t of the response of o v e r a l l m e d i c a l / s u r g i c a l use but the p r o p o r t i o n of s u r g i c a l admis s ions o f the t o t a l m e d i c a l / s u r g i c a l admis s ions i s about 33 p e r c e n t , one can conc lude t h a t the s t r e n g t h of the e f f e c t from beds t o use i s o n l y about o n e - f i f t h as g r e a t f o r su r ge ry as i t i s f o r o v e r a l l u se . By comparing the r e g r e s s i o n c o e f f i c i e n t s on BEDS i n more r e s t r i c t e d su r ge ry equa t i on s to the e q u a t i o n f o r o v e r a l l s u r g i c a l admiss ions one can f i n d t h a t the e f f e c t of p a e d i a t r i c bed a v a i l a b i l i t y i s r e l a t i v e l y s t r o n g e r on s u r g i c a l admiss ions e x c l u d i n g T&As and on SURG A admi s s ions than on o v e r a l l s u r g i c a l admi s s i on s . The c o e f f i c i e n t f o r SURG-T&A i s 92 p e r c e n t o f the c o e f f i c i e n t f o r 156 o v e r a l l s u r g e r y , but SURG-T&A admiss ions form o n l y 66 p e r c e n t of the t o t a l s u r g i c a l admiss ions (as d e r i v e d from T a b l e 9) i m p l y i n g n e a r l y 40 p e r c e n t g r e a t e r bed supp l y e f f e c t f o r SURG-T&A than f o r o v e r a l l s u r ge ry . Fo r SURG A the r e l a t i v e e f f e c t i s n e a r l y 20 p e r c e n t g r e a t e r than f o r o v e r a l l s u r g e r y . T h i s suggests t o the n e c e s s i t y t o c o n t r o l f o r the e f f e c t o f bed a v a i l a b i l i t y even when examining the r e l a t i o n s h i p of day ca re s u r g e r y a v a i l a b i l i t y t o these more r e s t r i c t e d measures of s u r g i c a l u t i l i z a t i o n . In s p i t e of the r e l a t i v e l y h i g h e r bed e f f e c t c o e f f i c i e n t t h e r e was more unexp l a i ned v a r i a t i o n i n the SURG A e q u a t i o n than i n the o v e r a l l s u r ge ry e q u a t i o n . The e f f e c t of bed a v a i l a b i l i t y on SURG B and SURG C was l e s s than one would expect by t h e i r share of the t o t a l s u r g i c a l l o a d when be ta c o e f f i c i e n t s were compared. A l s o the unexp l a i ned v a r i a t i o n f o r the se t ype of s u r ge ry was h i g h e r than f o r t o t a l s u r g e r y . 4.4 A d j u s t i n g f o r t h e e f f e c t o f bed s u p p l y Both s imp le c o r r e l a t i o n s and t h e o r y , suggest the need to i n c l u d e bo th BEDS and DCS i n a t tempt ing t o e x p l a i n v a r i a t i o n i n p a e d i a t r i c i n p a t i e n t use . I f p a e d i a t r i c bed a v a i l a b i l i t y e x p l a i n s the v a r i a t i o n i n day ca re su r ge ry a v a i l a b i l i t y and i n p a t i e n t u t i l i z a t i o n (Roemer's Law), then one would expect t o f i n d a dec rea se i n the s t r e n g t h of the r e l a t i o n s h i p between day c a r e s u r g e r y a v a i l a b i l i t y and i n p a t i e n t u t i l i z a t i o n when 157 the bed v a r i a b l e i s i n c l u d e d i n the e q u a t i o n . T a b l e 18 shows t h a t t h i s i s e x a c t l y what happens. When the r e l a t i o n s h i p between DCS and t o t a l m e d i c a l / s u r g i c a l admis s ions i s a d j u s t e d f o r bed a v a i l a b i l i t y , any e f f e c t of DCS on i n p a t i e n t u t i l i z a t i o n i s v i r t u a l l y e l i m i n a t e d . In f a c t , DCS shows a p o s i t i v e e f f e c t on MED/SURG admiss ions i n a l l yea r s except 1981/82 and 1982/83. In the equa t i ons f o r p a t i e n t days the r e g r e s s i o n c o e f f i c i e n t on DCS was p o s i t i v e even i n the se two l a t e r y e a r s . P a e d i a t r i c bed a v a i l a b i l i t y has a p o w e r f u l and s t a t i s t i c a l l y h i g h l y s i g n i f i c a n t impact on t o t a l m e d i c a l / s u r g i c a l admiss ions and p a t i e n t days even when the e f f e c t of day ca re su r ge ry a v a i l a b i l i t y i s c o n t r o l l e d . The goodness of f i t o f the o v e r a l l equa t i ons were v i r t u a l l y the same i n c o r r e s p o n d i n g equat ions i n T a b l e 16 and 18. DCS c o n t r i b u t e d v i r t u a l l y n o t h i n g t o the p r o p o r t i o n o f v a r i a t i o n accounted f o r by the BEDS and DCS v a r i a b l e s . Reg re s s i on a n a l y s i s f o r the t o t a l s u r g i c a l i n p a t i e n t c a re showed l e s s marked changes i n be ta c o e f f i c i e n t on DCS when the e f f e c t of BEDS was s t a n d a r d i z e d (Tab le 18) compared t o the c o e f f i c i e n t i n the equa t i on w i t h o n l y the DCS v a r i a b l e (Tab le 14) . The adjustment f o r bed a v a i l a b i l i t y r e s u l t e d i n a lmost no changes t o the DCS c o e f f i c i e n t s i n 1970-1973. In 1974 and 1975 the c o e f f i c i e n t on DCS tu rned from n e g a t i v e t o p o s i t i v e and i n the y e a r s 1976, 1981/82 and 1982/83 the c o e f f i c i e n t dec rea sed i n v a l u e and s i g n i f i c a n c e a l though remained n e g a t i v e . The be ta c o e f f i c i e n t on DCS d i f f e r e d from zero a t Table 18 School District Inpatient Hospital Utilization Equations with DCS and BEDS Variables by Year Admissions Days Measure & Year DCS SE BEDS SE CONST R2 SE Y DCS SE BEDS SE CONST R2 SE Y MED/SURG: 1968 0.73 1.26 29.803 3.75 60.36 0.4526 47.09 0.61 8.23 280.613 24.44 151.97 0.6391 306.76 1969 0.52 0.82 30.493 3.13 47.29 0.5602 42.38 1.90 6.36 269.323 24.35 107.97 0.6245 330.12 1970 0.10 0.79 28.243 3.57 55.54 0.4553 50.55 6.79 5.88 257.033 26.56 56.28 0.5536 376.21 1971 0.45 0.55 26.143 2.34 49.71 0.6233 38.98 3.44 4.09 211.733 17.32 131.31 0.6661 288.04 1972 1.23 0.73 25.033 2.39 47.23 0.5920 42.07 3.47 4.81 207.743 15.77 138.27 0.6996 277.06 1973 0.90 0.71 26.l l 3 2.83 40.19 0.5289 45.15 3.82 3.68 204.503 14.63 54.40 0.7250 233.19 1974 0.11 0.54 25.763 2.14 47.74 0.6659 32.65 1.27 3.16 211.343 12.48 31.44 0.7991 190.11 1975 0.10 0.53 23.403 2.04 45.47 0.6525 30.73 3.89 2.93 182.793 11.33 23.65 0.7843 170.42 1976 0.11 0.51 24.39s 2.01 38.76 0.6833 29.47 2.24 3.46 184.993 13.57 6.71 0.7290 198.68 1981/82 -0.29 0.39 19.633 1.66 51.16 0.6769 23.73 2.92 1.87 98.743 7.86 119.92 0.6829 112.63 1982/83 -0.33 0.45 20.923 2.12 45.21 0.5960 26.97 2.32 2.20 102.103 10.27 110.24 0.5752 130.92 SURG: 1968 0.03 0.40 0.74 1.20 58.71 -0.0224 15.05 0.31 1.87 27.703 5.54 234.14 0.2379 69.56 1969 -0.01 0.26 0.84 0.98 50.34 -0.0082 13.24 -0.06 1.23 22.953 4.72 201.97 0.2331 63.97 1970 -0.17 0.19 1.09 0.86 49.96 0.0109 12.24 0.52 1.15 18.353 5.21 195.85 0.1232 73.82 1971 -0.25 0.13 0.48 0.56 50.20 0.0347 9.28 -0.01 0.82 18.153 3.47 180.25 0.2572 57.72 1972 0.28 0.18 1.361 0.59 38.09 0.0619 10.45 1.20 1.00 19.823 3.28 149.07 0.3191 57.66 1973 0.24 0.18 0.96 0.72 38.12 0.0137 11.53 0.67 0.98 21.183 3.89 137.95 0.2725 61.98 1974 0.04 0.15 1.602 0.60 36.85 0.0642 9.20 0.35 0.97 24.313 3.83 127.38 0.3457 58.41 1975 0.07 0.14 2.573 0.55 30.09 0.2156 8.30 1.05 0.73 18.793 2.81 118.02 0.3667 42.29 1976 -0.01 0.14 1.762 0.55 31.22 0.1137 8.07 -0.98 0.73 11.863 2.86 154.07 0.2388 41.78 1981/82 -0.18 0.11 2.213 0.45 29.28 0.2983 6.50 0.09 0.64 12.813 2.68 104.24 0.2305 38.48 1982/83 -0.261 0.11 2.783 0.53 26.15 0.3509 6.82 -0.20 0.80 15.873 3.76 96.33 0.1963 47.93 p < 0.05 p < 0.01 p < 0.001 159 the f i v e p ercent s i g n i f i c a n c e l e v e l o n l y i n the 1982/83 admissions e q u a t i o n , i m p l y i n g a s u b s t i t u t i o n e f f e c t of 26 p e r c e n t and a g e n e r a t i o n e f f e c t of 74 p e r c e n t i n t h a t year. The change i n c o e f f i c i e n t on DCS i n the e q u a t i o n f o r s u r g i c a l days was much more marked than i n the equation f o r admissions. The c o e f f i c i e n t turned from n e g a t i v e t o p o s i t i v e i n almost a l l years when p a e d i a t r i c bed a v a i l a b i l i t y was e n t e r e d i n t o the equation (Tables 14 and 18). The r e g r e s s i o n c o e f f i c i e n t on DCS d i d not have s t a t i s t i c a l s i g n i f i c a n c e i n any of the study y e a r s . The p a e d i a t r i c bed a v a i l a b i l i t y measure had almost the same e f f e c t on o v e r a l l s u r g i c a l admissions and days r e g a r d l e s s of the s t a n d a r d i z a t i o n f o r day care surgery a v a i l a b i l i t y (Tables 16 and 18). The c o e f f i c i e n t on BEDS was s t a t i s t i c a l l y s i g n i f i c a n t i n a l l study years i n the equation f o r s u r g i c a l days and i n years 1972, 1974-1976, 1981/82 and 1982/83 i n the e q u a t i o n f o r s u r g i c a l admissions. The p r o p o r t i o n of the v a r i a t i o n i n s u r g i c a l i n p a t i e n t u t i l i z a t i o n accounted f o r by the DCS/BEDS model was almost i d e n t i c a l t o the p r o p o r t i o n accounted f o r by BEDS alone, as would be expected g i v e n the l a c k of s i g n i f i c a n c e of the DCS v a r i a b l e alone. The r e s u l t s i n Table 18 support the hypothesis t h a t p a e d i a t r i c day care surgery does not have any independent e f f e c t on t o t a l or s u r g i c a l i n p a t i e n t u t i l i z a t i o n . The o n l y 160 mean ing fu l t r a c e of p o s s i b l e s u b s t i t u t i o n o f day c a r e su r ge ry f o r i n p a t i e n t ca re was i n 1982/83. The c o e f f i c i e n t on DCS i n the e q u a t i o n f o r t o t a l m e d i c a l / s u r g i c a l u t i l i z a t i o n i n d i f f e r e n t s tudy yea r s p r o v i d e s a r ea sonab le b a s i s from which to conc lude t h a t day c a r e su r ge ry a v a i l a b i l i t y has had no e f f e c t on o v e r a l l m e d i c a l / s u r g i c a l i n p a t i e n t u t i l i z a t i o n i n the p a e d i a t r i c p o p u l a t i o n i n B.C. over the p e r i o d 1968-1976 and i n 1981/82-1982/83. The i n t e r p r e t a t i o n o f T a b l e 18 w i t h r e s p e c t t o o v e r a l l s u r g i c a l i n p a t i e n t u t i l i z a t i o n i s v e r y much the same as f o r o v e r a l l h o s p i t a l u se . Day c a r e s u r g e r y a v a i l a b i l i t y does not appear t o have had any s i g n i f i c a n t e f f e c t on s u r g i c a l i n p a t i e n t u t i l i z a t i o n i n d i f f e r e n t s tudy y e a r s . The y e a r 1982/83 i s the o n l y e x c e p t i o n . But even here the n e g a t i v e c o e f f i c i e n t on DCS f o r both s u r g i c a l admiss ions and days i m p l i e s t h a t one day c a r e su r ge ry case " saves " 0.26 i n p a t i e n t admis s ions w i t h an average l e n g t h of s t a y o f l e s s than a day. S i n c e average l e n g t h of s t a y o f i n p a t i e n t s can never be l e s s than one, t h i s c a s t s doubt on a s u b s t i t u t i o n i n t e r p r e t a t i o n even i n t h a t y e a r . The r e s u l t s i n T a b l e 18 do g i v e support t o the h y p o t h e s i s t h a t p a e d i a t r i c bed a v a i l a b i l i t y has an independent impact on h o s p i t a l i n p a t i e n t use . The be ta c o e f f i c i e n t s on BEDS show a c o n s i s t e n t p a t t e r n from y e a r t o y e a r , and may be i n t e r p r e t e d as i m p l y i n g t h a t the a d d i t i o n of each bed i n c r e a s e d m e d i c a l / s u r g i c a l admiss ions by about 25-30, o f which s u r g i c a l admi s s ions accounted f o r about 1-2. These a d d i t i o n a l 161 admissions i n v o l v e d lengths of s t a y f a l l i n g from about 10 to 5 days over time, w i t h the s u r g i c a l l e ngths of s t a y b e ing much lo n g e r (25 down t o under 6 days i n 1982/83). In T a b l e 19, r e g r e s s i o n c o e f f i c i e n t s on DCS f o r d i f f e r e n t s u r g i c a l u t i l i z a t i o n measures are r e p o r t e d , i n c o r p o r a t i n g the adjustment f o r p a e d i a t r i c bed a v a i l a b i l i t y . Comparing Tables 15 and 19 shows t h a t i n 1971 the DCS e f f e c t was not much a f f e c t e d by the adjustment f o r bed a v a i l a b i l i t y , but i n 1976 and 1981/82 the s t a n d a r d i z a t i o n f o r the e f f e c t of BEDS reduced markedly the a s s o c i a t i o n between DCS and the d i f f e r e n t s u r g i c a l u t i l i z a t i o n measures. The narrowest s u r g i c a l u t i l i z a t i o n measure (SURG C) showed the l e a s t change due t o bed adjustment. However, t h a t a s s o c i a t i o n was v e r y weak i n the f i r s t p l a c e . The c o e f f i c i e n t s on BEDS v a r i a b l e were almost the same i n s p i t e of the adjustment f o r DCS (Tables 17 and 19). A l s o i n 1976 and 1981/82 the v a r i a n c e of d i f f e r e n t i n p a t i e n t u t i l i z a t i o n measures accounted f o r by the DCS/BEDS model was almost the same as by the s o l e BEDS model. Day care s u r g e r y a v a i l a b i l i t y seems t o c o n t r i b u t e t o the o v e r a l l goodness of f i t of the r e g r e s s i o n equation o n l y w i t h SURG B days i n 1981/82. In 1971, the goodness of f i t of the o v e r a l l e quations w i t h SURG A and SURG B measures (admissions and days) i s improved by the i n c l u s i o n of the DCS v a r i a b l e . The r e s u l t s i n 1971 i n Table 19 r a i s e the p o s s i b i l i t y of a s u b s t i t u t i o n e f f e c t of day care surgery w i t h i n the narrower Table 19 School District Inpatient Hospital Utilization Equations with DCS and BEDS in 1971. 1976, 1981/82, Pooled 1968-1976 and Pooled 1968-1982/83 Dataset Admissions Days Year & Measure DCS SE BEDS SE CONST R2 SE Y DCS SE BEOS SE CONST R2 SE Y 1971 MED/SURG 0.45 0.55 26.143 2.34 49.71 0.6233 38.98 3.44 4.09 211.733 17.32 131.31 0.6661 288.04 SURG -0.25 0.13 0.48 0.56 50.20 0.0347 9.28 -0.01 0.82 18.153 3.47 180.25 0.2572 57.72 SURG-TSA -0.03 0.09 1.743 0.36 34.77 0.2302 5.97 0.55 0.79 19.593 3.34 128.09 0.3043 55.62 SURG A -0.311 0.12 0.15 0.51 37.74 0.0613 8.44 -0.801 0.39 5.192 1.65 97.69 0.1540 27.38 SURG B -0.281 0.11 -0.46 0.48 35.32 0.0582 8.01 -0.611 0.25 -0.36 1.04 74.02 0.0544 17.30 SURG C -0.05 0.04 0.06 0.17 8.64 -0.0036 2.89 -0.07 0.09 0.38 0.38 18.03 -0.0040 6.32 1976 MEO/SURG 0.11 0.51 24.393 2.01 38.76 0.6833 29.47 2.24 3.46 184.993 13.57 6.71 0.7290 198.68 SURG -0.01 0.14 1.763 0.55 31.22 0.1137 8.07 -0.98 0.73 11.863 2.86 154.07 0.2388 41.78 SURG-T&A 0.02 0.09 1.132 0.35 22.48 0.1084 5.16 -0.69 0.72 10.303 2.83 132.55 0.1798 41.47 SURG A -0.01 0.12 1.442 0.46 18.69 0.1113 6.68 -0.06 0.37 7.513 1.47 43.15 0.2734 21.46 SURG B -0.01 0.12 0.991 0.45 17.45 0.0441 6.63 -0.23 0.25 2.431 0.99 38.94 0.0888 14.50 SURG C 0.01 0.04 0.29 0.16 6.07 0.0194 2.28 0.00 0.09 0.892 0.33 12.40 0.0746 4.89 1981/82 MED/SURG -0.29 0.39 19.633 1.66 51.16 0.6769 23.73 2.92 1.87 98.743 7.86 119.92 0.6829 112.63 SURG -0.18 0.11 2.213 0.45 29.28 0.2983 6.50 0.09 0.64 12.813 2.68 104.24 0.2305 38.48 SURG-T&A -0.11 0.08 1.963 0.33 21.31 0.3614 4.78 0.36 0.62 12.393 2.62 85.12 0.2207 37.48 SURG A -0.13 0.08 1.072 0.34 15.57 0.1637 4.88 -0.22 0.20 5.243 0.83 28.59 0.3929 11.92 SURG B -0.13 0.08 0.65 0.33 15.32 0.0813 4.78 -0.361 0.15 1.17 0.64 32.58 0.1229 9.11 SURG C -0.05 0.04 0.371 0.16 4.94 0.0955 2.24 -0.12 0.07 0.691 0.31 10.48 0.1049 4.38 .Continued Table 19 School District Inpatient Hospital Utilization Equations with OCS and BEDS in 1971. 1976. 1981/82. Pooled 1968-1976 and Pooled 1968-1982/83 Dataset Admissions Days Year & Measure DCS SE BEDS SE CONST R2 SE Y DCS SE BEDS SE CONST R2 SE Y Pooled MED/SURG -0.26 0.22 25.443 0.91 59.32 0.5417 42.02 -4.692 1.57 208.543 6.67 209.31 0.6033 306.77 1968-76 SURG -0.383 0.06 0.802 0.Z8 48.67 0.0648 12.65 -2.073 0.37 16.943 1.55 203.92 0.2003 71.18 SURG-T&A -0.082 0.03 1.273 0.15 26.57 0.1133 6.72 -1.143 0.32 16.963 1.34 155.09 0.2159 61.73 SURG A -0.403 0.06 0.521 0.24 35.31 0.0805 10.95 -1.533 0.20 6.803 0.86 96.00 0.1659 39.71 SURG B -0.333 0.05 -0.03 0.22 32.08 0.0544 10.10 -0.873 0.11 0.55 0.48 69.09 0.0825 22.27 SURG C 0.01 0.01 0.11 0.06 7.23 0.0025 2.74 -0.02 0.03 0.473 0.14 16.03 0.0166 6.27 Pooled MED/SURG -0.773 0.17 25.023 0.81 62.16 0.5620 40.73 -8.393 1.32 195.133 6.17 253.83 0.5856 308.54 1968-83 SURG -0.613 0.05 1.233 0.25 47.71 0.1775 12.68 -3.163 0.31 17.383 1.44 202.98 0.2730 72.10 SURG-T&A -0.183 0.03 1.483 0.13 26.21 0.1925 6.69 -1.993 0.27 17.133 1.24 155.17 0.2652 62.08 SURG A -0.643 0.05 0.823 0.23 34.69 0.2056 11.29 -2.313 0.17 7.133 0.82 95.60 0.2724 40.75 SURG B -0.533 0.04 0.27 0.21 31.45 0.1632 10.24 -1.333 0.10 1.081 0.45 68.11 0.2051 22.67 SURG C -0.063 0.01 0.213 0.06 7.19 0.0534 2.83 -0.183 0.03 0.663 0.13 16.03 0.0913 6.47 1 p < 0.05 2 p < 0.01 3 p < 0.001 164 p a e d i a t r i c s u r g i c a l c a t e g o r i e s . However, t h e r e i s some i n d i c a t i o n t h a t something e l s e may l i e beh ind these r e s u l t s . The r e s u l t s of the SURG equa t ions i n T a b l e 18 suggest t h a t the y e a r 1971 i s d i f f e r e n t from the o t h e r y e a r s . The y e a r 1971 showed a n e g a t i v e a s s o c i a t i o n between DCS and o v e r a l l s u r g i c a l a d m i s s i o n s . T a b l e 19 i m p l i e s t h a t t h i s a s s o c i a t i o n i s ma in l y due t o the DCS " e f f e c t " on T&A u t i l i z a t i o n . DCS had a lmost no e f f e c t on "non-T&A" s u r g i c a l u t i l i z a t i o n i n 1971. In a d d i t i o n , T a b l e 9 r e v e a l e d a g r e a t e r drop i n the i n p a t i e n t T&A r a t e i n 1970-1971 than i n the su r round ing y e a r s . I t seems t h a t e i t h e r day c a r e s u r g e r y has s u b s t i t u t e d f o r i n p a t i e n t T&As i n 1971 t o a major e x t e n t o r , more p l a u s i b l y , the d e c l i n e i n T&A r a t e and c o i n c i d i n g i n c r e a s e i n day ca re su r ge ry r a t e i n t h i s y e a r took p l a c e c o n c u r r e n t l y but i n d e p e n d e n t l y , and no r e a l s u b s t i t u t i o n o c c u r r e d . The y e a r 1971 can a l s o r e f l e c t a ' m e d i c a l p r o g r e s s i v i t y ' e f f e c t ; ' p r o g r e s s i v e ' p h y s i c i a n s were do ing l e s s T&As and more day ca re su r ge ry as a r e s u l t of s h i f t s i n m e d i c a l knowledge and techno logy . A l though the r e g r e s s i o n c o e f f i c i e n t on DCS f o r o v e r a l l m e d i c a l / s u r g i c a l admiss ions was p o s i t i v e i n n i n e of the e l e v e n s tudy y e a r s , i t was n e g a t i v e and s t a t i s t i c a l l y h i g h l y s i g n i f i c a n t i n the poo led 1968-1982/83 c r o s s - a r e a / c r o s s - y e a r da ta (Tab le 19) . On the o t h e r hand, day ca re s u r g e r y a v a i l a b i l i t y added v e r y l i t t l e t o the goodness of f i t of the o v e r a l l e q u a t i o n . The poo led equa t i on (1968-1982/83) i m p l i e s t h a t 100 c h i l d r e n admi t ted t o a day c a r e su r ge ry u n i t would 165 have saved 77 i n p a t i e n t admi s s i on s . The average l e n g t h of s t a y of " saved" i n p a t i e n t s would have been 10.9 day s , which i s f a r too h i g h t o be c o n s i d e r e d p l a u s i b l e . The s t r i k i n g d i f f e r e n c e i n the c o e f f i c i e n t between i n d i v i d u a l y e a r da ta and the p o o l e d da ta t h a t i s a l s o seen w i t h o t h e r measures o f i n p a t i e n t u t i l i z a t i o n can be e x p l a i n e d , a t l e a s t p a r t l y , by the s imu l taneous and o b v i o u s l y independent t r e n d s o f d e c r e a s i n g s u r g i c a l (T&A) u t i l i z a t i o n and i n c r e a s i n g day ca re s u r g e r y a v a i l a b i l i t y . The o v e r a l l p a e d i a t r i c h o s p i t a l u t i l i z a t i o n may have f a l l e n over t ime i r r e s p e c t i v e o f the i n c r e a s e i n day ca re su r ge ry c a p a c i t y . I f day c a r e s u r g e r y a v a i l a b i l i t y was c a u s a l l y r e l a t e d to o v e r a l l p a e d i a t r i c i n p a t i e n t u t i l i z a t i o n , one would expect t o see n e g a t i v e r e g r e s s i o n c o e f f i c i e n t s a l s o i n i n d i v i d u a l y e a r e q u a t i o n s . A l l t h i s p o i n t s t o the n e c e s s i t y t o c o n t r o l f o r e f f e c t s o f measured and unmeasured t ime-dependent confound ing f a c t o r s when a n a l y z i n g the poo led d a t a s e t . The a s s o c i a t i o n of DCS w i th o v e r a l l s u r g i c a l u t i l i z a t i o n was a l s o s t r o n g e r i n the poo led da ta than i n the i n d i v i d u a l yea r d a t a , o b v i o u s l y f o r the above mentioned r e a s o n . The d i f f e r e n c e between p o o l e d da t a and i n d i v i d u a l y e a r da ta was a l r e a d y i l l u s t r a t e d i n F i g u r e 3. The c o e f f i c i e n t s from the poo led da ta imp l y t h a t 100 day ca re su r ge ry cases would have saved 61 s u r g i c a l admis s ions w i t h average l e n g t h of s t a y o f 5.2 days (Tab le 19). 166 The beta c o e f f i c i e n t on DCS showed i n c r e a s e i n v a l u e and s i g n i f i c a n c e a l s o f o r other measures of s u r g i c a l i n p a t i e n t u t i l i z a t i o n when moving from i n d i v i d u a l year data t o pooled data (Table 19). The i n c r e a s e i n v a l u e was lowest w i t h SURG C equ a t i o n s . The r e g r e s s i o n c o e f f i c i e n t s on DCS f o r SURG-T&A and SURG C admissions were c l e a r l y lower than f o r o t h e r s u r g i c a l admissions. I f DCS was causing the d e c l i n e i n T&As one would expect t o f i n d s t r o n g e r n e g a t i v e c o e f f i c i e n t s on DCS f o r those measures of s u r g i c a l u t i l i z a t i o n t h a t i n c l u d e T&As than f o r SURG-T&A or SURG C both i n the pooled data and i n the i n d i v i d u a l year d a t a , although t h e r e are s t i l l p o t e n t i a l m i s s i n g v a r i a b l e s i n both s e t s of the data a n a l y s i s . However, s t r o n g e r c o e f f i c i e n t s were found o n l y i n s i x of the e l e v e n study y e a r s . In 1969-1971 the d i f f e r e n c e was c l e a r , i n 1976 and 1981/82 - 1982/83 the c o e f f i c i e n t s were o n l y s l i g h t l y s t r o n g e r (equations are presented o n l y f o r the years 1971, 1976 and 1981/82) (Table 19). Thus, the c o e f f i c i e n t s i n the pooled data should be i n t e r p r e t e d w i t h c a u t i o n . The s t r e n g t h of the a s s o c i a t i o n between p a e d i a t r i c bed a v a i l a b i l i t y and i n p a t i e n t u t i l i z a t i o n was i n the same range both i n the i n d i v i d u a l year data and i n the pooled data (Table 19). A l s o , the r e g r e s s i o n c o e f f i c i e n t s on BEDS f o r the o v e r a l l m e d i c a l / s u r g i c a l u t i l i z a t i o n equations were almost the same i n the pooled d a t a s e t b e f o r e and a f t e r the adjustment f o r DCS (Tables 17 and 19). However, the adjustment f o r DCS decreased 167 s l i g h t l y the s t r e n g t h of the a s s o c i a t i o n between BEDS and d i f f e r e n t measures of s u r g i c a l u t i l i z a t i o n i n t h i s d a t a s e t . T a b l e 19 p r e s e n t s a l s o the r e s u l t s o f r e g r e s s i o n ana l y se s on the s h o r t e r poo led d a t a s e t , the 1968-1976 c r o s s - a r e a / c r o s s -y e a r d a t a . T h i s t ime range was s t u d i e d s e p a r a t e l y i n o r d e r to be a b l e to compare the r e g r e s s i o n r e s u l t s t o the p r e v i o u s s tudy t h a t was c a r r i e d out on the t o t a l p o p u l a t i o n (Evans s ± a l . f 1983). T h i s d a t a s e t r e v e a l e d the same s o r t s o f d i f f e r e n c e s i n r e s u l t s from the s i n g l e y e a r e q u a t i o n s , but the d i f f e r e n c e s were not so prominent . By the end of 1982/83 day c a r e s u r g e r y had i n c r e a s e d and T&A u t i l i z a t i o n dec rea sed so much t h a t one would expect t o get a s t e e p e r downward r e g r e s s i o n l i n e than w i t h the d a t a s e t t h a t ends i n 1976. On the b a s i s of r e s u l t s i n each i n d i v i d u a l y e a r i n T a b l e 19, one c o u l d conc lude t h a t day ca re su r ge ry a v a i l a b i l i t y has not had any e f f e c t on t o t a l p a e d i a t r i c i n p a t i e n t u t i l i z a t i o n and v e r y l i t t l e e f f e c t , i f any, on more na r row ly d e f i n e d s u r g i c a l i n p a t i e n t u se . But the equa t i on s w i t h the poo led da t a suggest some e f f e c t . 4.5 N o n - l i n e a r bed e f f e c t I t has been suggested t h a t the r e l a t i o n s h i p between h o s p i t a l u t i l i z a t i o n and bed a v a i l a b i l i t y may not be l i n e a r but c u r v i l i n e a r (Evans e t a l . f 1983). In o t h e r words, when bed 168 a v a i l a b i l i t y i s low, one a d d i t i o n a l bed l eads t o a g r e a t e r i n c r e a s e i n u t i l i z a t i o n than one a d d i t i o n a l bed i n a s i t u a t i o n where beds a r e numerous. E v e n t u a l l y s a t u r a t i o n might s e t i n , and a t h i gh enough c a p a c i t y l e v e l s f u r t h e r beds would j u s t s tand empty. In o r d e r t o t e s t t h i s h y p o t h e s i s , and t o r e f i n e the measure o f bed a v a i l a b i l i t y , r e g r e s s i o n equa t i ons f o r each measure of i n p a t i e n t u t i l i z a t i o n were e s t ima ted u s i n g BEDS and BEDS 2 (or BEDSQ) i n the poo led da ta (Tab le 2 0 ) . The squared measure of bed a v a i l a b i l i t y f o r c e s a q u a d r a t i c f u n c t i o n r a t h e r than a l i n e through the s c a t t e r of u t i l i z a t i o n / b e d s combinat ions i n the da ta s e t . I f the squared term has a c o e f f i c i e n t e q u a l t o z e r o , then the r e l a t i o n s h i p between bed a v a i l a b i l i t y and i n p a t i e n t u t i l i z a t i o n i s be s t d e s c r i b e d by a s t r a i g h t l i n e . But i f i t has a n e g a t i v e c o e f f i c i e n t , as i n T a b l e 2 0 , then the r e l a t i o n s h i p i s be s t d e s c r i b e d by a concave curved l i n e . The c o e f f i c i e n t on BEDS 2 was n e g a t i v e and s t a t i s t i c a l l y h i g h l y s i g n i f i c a n t i n a l l s i x e q u a t i o n s . However, the c o n t r i b u t i o n t o the p r o p o r t i o n of v a r i a n c e e x p l a i n e d by the model was not v e r y d r a m a t i c . The improvement i n R 2 r e l a t i v e t o equa t i on s w i t h o n l y BEDS was g r e a t e r f o r d i f f e r e n t s u r g i c a l measures than f o r m e d i c a l / s u r g i c a l u t i l i z a t i o n . In s p i t e of the r e l a t i v e l y low i n f l u e n c e on the e x p l a i n e d v a r i a n c e , the BEDS 2 term was always s i g n i f i c a n t , sugges t ing t h a t a c u r v i l i n e a r f i t i s s u p e r i o r t o an assumption of l i n e a r i t y . 169 Table 20 School District Inpatient Hospital Utilization Equations with BEDS and BEDSQ in Pooled 1968-82/83 Dataset Measure BEDS SE BEDSQ SE CONST R2 SE Y Admissions: MED/SURG 25.743 0.81 - - 50.20 0.5521 41.19 39.653 2.66 -1.413 0.26 23.70 0.5673 40.49 SURG 1.793 0.27 - - 38.21 0.0509 13.62 6.273 0.88 0.453 0.09 1.89 0.0814 13.40 SURG-T&A 1.653 0.13 - - 23.41 0.1544 6.85 3.733 0.44 -0.213 0.04 19.46 0.1774 6.75 SURG A 1.413 0.24 - - 24.80 0.0378 12.42 4.723 0.81 -0.333 0.08 18.50 0.0577 12.29 SURG B 0.763 0.22 - - 23.19 0.0135 11.12 3.563 0.73 -0.283 0.07 17.87 0.0315 11.02 SURG C 0.273 0.06 - - 6.26 0.0257 2.87 0.953 0.19 -0.073 0.02 4.95 0.0417 2.84 Days: MED/SURG 202.903 6.19 - - 123.94 0.5658 315.84 269.993 20.65 -6.783 1.99 -3.89 0.5713 313.82 SURG 20.313 1.50 - - 154.07 0.1813 76.51 45.813 4.95 -2.583 0.48 105.47 0.2083 75.24 SURG-T&A 18.973 1.26 - - 124.33 0.2159 64.13 37.993 4.16 -1.923 0.40 99.09 0.2362 63.29 SURG A 9.273 0.88 - - 59.81 0.1180 44.87 21.603 2.92 -1.253 0.28 36.32 0.1374 44.37 SURG B 2.313 0.49 - - 47.53 0.0249 25.11 8.513 1.64 -0.633 0.16 35.73 0.0420 24.89 SURG C 0.823 0.13 - - 13.23 0.0453 6.63 2.003 0.43 -0.122 0.04 10.99 0.0535 6.60 1 p < 0.05 2 p < 0.01 3 p < 0.001 170 A c c o r d i n g t o the l i n e a r model i n T a b l e 20 one a d d i t i o n a l bed would i n c r e a s e t o t a l m e d i c a l / s u r g i c a l admis s ions by 25.74 cases and h o s p i t a l days by 202.90 i r r e s p e c t i v e l y o f the l e v e l of e x i s t i n g bed c a p a c i t y . A c c o r d i n g t o the c u r v i l i n e a r model one a d d i t i o n a l bed per 1,000 p o p u l a t i o n a t e x i s t i n g bed c a p a c i t y of 2 beds pe r 1,000 p o p u l a t i o n (BEDS = 2) would i n c r e a s e t o t a l m e d i c a l / s u r g i c a l admiss ions p e r 1,000 p o p u l a t i o n by 34.01 (39.65 - 2(1.41)BEDS) and days p e r 1,000 p o p u l a t i o n by 242.87 (269.99 - 2(6.78)BEDS) i m p l y i n g a m a r g i n a l occupancy r a t e of 66.5 p e r c e n t and a l e n g t h of s t a y of 7.1 days . But a t the e x i s t i n g c a p a c i t y l e v e l of 4 beds per 1,000 p o p u l a t i o n (BEDS = 4) one a d d i t i o n a l bed would l e a d to o n l y 28.37 admiss ions and 215.75 p a t i e n t days , i m p l y i n g a m a r g i n a l l e n g t h of s t a y of 7.6 days and occupancy r a t e of 59.1 p e r c e n t . Thus, the Roemer e f f e c t would appear to weaken as c a p a c i t y expands, but i t remains i n f o r c e up t o v e r y h i gh l e v e l s of bed c a p a c i t y . The l e v e l o f c a p a c i t y a t which more beds w i l l i nduce no f u r t h e r admiss ions o r p a t i e n t days can be found by s e t t i n g the d e r i v a t i v e s o f the c u r v i l i n e a r equa t i on s to z e r o , and s o l v i n g f o r beds, t h u s : 39.65 - 2(1.41) BEDS = 0 269.99 - 2(6.78) BEDS = 0 t o y i e l d BEDS = 14.06 and 19.91 (per 1,000 p o p u l a t i o n ) r e s p e c t i v e l y . These s a t u r a t i o n l e v e l s a r e , of c o u r s e , more or l e s s t h e o r e t i c a l s i n c e they a re beyond the range of 171 o b s e r v a t i o n s . The h i g h e s t b e d - t o - p o p u l a t i o n r a t i o i n these data was 13/1,000. The r e l a t i o n s h i p between bed c a p a c i t y and l e n g t h of s t a y i s a l s o i n t e r e s t i n g . When bed c a p a c i t y i n c r e a s e s , the m a r g i n a l l e n g t h of s t a y i n c r e a s e s , although not v e r y d r a m a t i c a l l y . I f one h y p o t h e s i z e d t h a t s e v e r i t y of i l l n e s s was c o r r e l a t e d w i t h l e n g t h of s t a y , and t h a t when beds are s c a r c e , l e s s severe cases are r a t i o n e d out, one might a n t i c i p a t e t h a t l e n g t h s of s t a y would f a l l as c a p a c i t y r i s e s . On the o t h e r hand, p h y s i c i a n s might respond t o bed s c a r c i t y by s h o r t e n i n g lengths of s t a y w h i l e t r y i n g to h o l d admission r a t e s c o n s t a n t . But h o s p i t a l p a e d i a t r i c bed occupancy r a t e s have known t o have been low i n a l l s c h o o l d i s t r i c t s throughout the p r o v i n c e d u r i n g the study p e r i o d , suggesting a l t e r n a t i v e e x p l a n a t i o n s . I t i s p o s s i b l e t h a t t h i s a s s o c i a t i o n r e f l e c t s a Roemer e f f e c t : beds are f i l l e d both by i n c r e a s i n g admissions but a l s o by i n c r e a s i n g l e n g t h s of s t a y . In an environment of low occupancy r a t e s t h i s i m p l i e s t h a t new demand f o r h o s p i t a l s e r v i c e s had been generated on a b a s i s o t h e r than medical needs. The next phase i n the a n a l y s i s was t o study the i n f l u e n c e of the improved bed c a p a c i t y measure on the r e l a t i o n s h i p of DCS and p a e d i a t r i c i n p a t i e n t use (Table 21). Comparison of r e g r e s s i o n c o e f f i c i e n t s on DCS i n t h i s t a b l e t o c o e f f i c i e n t s i n Table 19 showed t h a t the impact of DCS on d i f f e r e n t measures of i n p a t i e n t u t i l i z a t i o n d i d not change a f t e r Table 21 School District Inpatient Hospital Utilization Equations with DCS, BEDS and BEDSQ in 1971. 1976. 1981/82. Pooled 1968-1976 and Pooled 1968-1982/83 Dataset Admissions Year & Measure DCS SE BEDS SE BEDSQ SE CONST R2 SE Y 1971 MED/SURG 0.42 SURG -0.25 SURG-T&A -0.04 SURG A -0.311 SURG B -0.281 SURG C -0.05 1976 MED/SURG 0.14 SURG 0.02 SURG-T&A 0.04 SURG A 0.01 SURG B 0.01 SURG C 0.02 1981/82 MED/SURG 0.03 SURG -0.15 SURG-T&A -0.08 SURG A -0.10 SURG B -0.09 SURG C -0.04 Pooled MED/SURG -0.24 1968-76 SURG -0.383 SURG-T&A -0.081 SURG A -0.403 SURG B -0.333 SURG C 0.01 Pooled MED/SURG -0.673 1968-83 SURG -0.583 SURG-T&A -0.173 SURG A -0.623 SURG B -0.523 SURG C -0.063 0.55 36.903 7.87 -0.96 0.13 2.09 1.89 -0.14 0.09 3.041 1.21 -0.12 0.12 -0.11 1.73 0.02 0.12 -0.60 1.64 0.01 0.04 0.04 0.59 0.00 0.52 28.971 6.90 -0.47 0.14 5.552 1.84 -0.381 0.09 3.702 1.17 -0.261 0.12 4.082 1.53 -0.27 0.11 3.801 1.52 -0.29 0.04 1.311 0.52 -0.101 0.40 33.403 5.46 -1.431 0.11 3.801 1.56 -0.16 0.08 3.011 1.15 -0.11 0.09 2.341 1.17 -0.13 0.08 2.271 1.14 -0.17 0.04 0.93 0.54 -0.06 0.21 38.183 3.09 -1.263 0.06 3.433 0.94 -0.262 0.03 2.593 0.50 -0.132 0.06 1.951 0.82 -0.14 0.05 1.01 0.75 -0.10 0.01 0.39 0.20 -0.03 0.17 37.823 2.68 -1.283 0.05 4.673 0.84 -0.353 0.03 3.273 0.44 -0.183 0.05 3.013 0.75 -0.222 0.04 2.132 0.68 -0.192 0.01 0.803 0.19 -0.062 0.67 27.07 0.6287 38.70 0.16 46.83 0.0319 9.29 0.10 22.03 0.2331 5.96 0.15 38.29 0.0484 8.50 0.14 35.61 0.0450 8.06 0.05 8.68 -0.0177 2.91 0.67 29.42 0.6810 29.58 0.18 23.49 0.1565 7.88 0.11 17.23 0.1584 5.02 0.15 13.28 0.1384 6.58 0.15 11.69 0.0795 6.51 0.05 3.98 0.0615 2.23 0.54 20.75 0.7015 22.80 0.15 25.77 0.2997 6.50 0.11 19.00 0.3605 4.78 0.12 12.76 0.1672 4.87 0.11 11.75 0.0966 4.74 0.05 3.70 0.0980 2.24 0.29 33.82 0.5534 41.48 0.09 43.42 0.0752 12.58 0.05 23.93 0.1220 6.69 0.08 32.45 0.0837 10.93 0.07 29.99 0.0559 10.09 0.02 6.67 0.0041 2.73 0.26 36.30 0.5744 40.15 0.08 40.75 0.1946 12.55 0.04 22.60 0.2088 6.62 0.07 30.26 0.2137 11.23 0.07 27.69 0.1704 10.20 0.02 6.00 0.0645 2.81 1 p < 0.05 2 p < 0.01 3 p < 0.001 .Cont inued Table 21 School District Inpatient Hospital Utilization Equations with DCS. BEDS and BEDSQ in 1971, 1976. 1981/82. Pooled 1968-1976 and Pooled 1968-1982/83 Dataset Days Year & Measure DCS SE BEDS SE BEDSQ SE CONST R2 SE Y 1971 MED/SURG 3.04 SURG -0.09 SURG-T&A 0.48 SURG A -0.801 SURG B -0.621 SURG C -0.06 1976 MED/SURG 1.63 SURG -0.78 SURG-T&A -0.52 SURG A -0.03 SURG B -0.20 SURG C 0.01 1981/82 MED/SURG 4.281 SURG 0.14 SURG-T&A 0.38 SURG A -0.32 SURG B -0.331 SURG C -0.11 Pooled MED/SURG -4.562 1968-76 SURG -2.033 SURG-T&A - l . l l 3 SURG A -1.513 SURG B -0.863 SURG C -0.02 Pooled MED/SURG -7.953 1968-83 SURG -2.993 SURG-T&A -1.863 SURG A -2.243 SURG B -1.303 SURG C -0.173 3.88 386.223 54.88 -15.532 0.77 52.963 11.01 -3.102 0.74 52.153 10.65 -2.902 0.39 7.31 5.60 -0.19 0.25 0.30 3.54 -0.06 0.09 -0.51 1.29 0.08 3.40 97.771 45.38 -S.861 0.69 40.323 9.15 -2.892 0.69 35.613 9.22 -2.572 0.38 11.511 5.02 -0.41 0.25 7.081 3.36 -0.47 0.09 1.66 1.14 -0.08 1.90 157.353 26.17 -6.061 0.67 15.20 9.27 -0.25 0.66 13.46 9.04 -0.11 0.21 3.10 2.86 0.22 0.16 2.65 2.19 -0.15 0.08 1.38 1.05 -0.07 1.56 273.313 22.73 -6.382 0.36 37.143 5.25 -1.993 0.31 32.903 4.56 -1.573 0.20 14.683 2.94 -0.782 0.11 2.99 1.66 -0.24 0.03 0.66 0.47 -0.02 1.33 248.133 20.55 -5.312 0.31 37.593 4.77 -2.033 0.27 32.873 4.11 -1.583 0.18 15.433 2.71 -0.832 0.10 4.942 1.51 -0.392 0.03 1.523 0.43 -0.091 4.67 -235.88 0.7071 269.78 0.94 107.00 0.3474 54.10 0.91 59.58 0.3834 52.36 0.48 93.22 0.1440 27.54 0.30 72.65 0.0415 17.42 0.11 19.91 -0.0107 6.34 4.41 184.82 0.7400 194.61 0.89 95.94 0.3282 39.25 0.90 80.87 0.2549 39.53 0.49 34.98 0.2703 21.51 0.33 29.45 0.1024 14.39 0.11 10.84 0.0680 4.91 2.59 -9.57 0.7015 109.28 0.92 98.97 0.2205 38.73 0.90 82.76 0.2099 37.74 0.28 33.33 0.3896 11.96 0.22 29.33 0.1167 9.14 0.10 8.97 0.0981 4.40 2.14 79.81 0.6079 304.97 0.49 163.54 0.2180 70.39 0.43 123.22 0.2300 61.17 0.28 80.25 0.1742 39.51 0.16 64.22 0.0844 22.24 0.04 15.65 0.0154 6.27 1.97 146.73 0.5888 307.37 0.46 162.16 0.2892 71.29 0.39 123.36 0.2785 61.52 0.26 78.84 0.2806 40.52 0.14 60.31 0.2111 22.58 0.04 14.27 0.0951 6.45 1 p < 0.05 2 p < 0.01 3 p < 0.001 174 i n c l u s i o n of BEDS 2 i n the model i n 1971. In 1976, the c o e f f i c i e n t remained s t a t i s t i c a l l y i n s i g n i f i c a n t i n a l l e q u a t i o n s . In 1981/82, the adjustment f o r BEDS 2 i n c r e a s e d the v a l u e of the p o s i t i v e r e g r e s s i o n c o e f f i c i e n t on DCS f o r MED/SURG days and changed i t t o s t a t i s t i c a l l y s i g n i f i c a n t . The n e g a t i v e c o e f f i c i e n t f o r SURG B days decreased i n v a l u e and became s t a t i s t i c a l l y a i n s i g n i f i c a n t . The r e g r e s s i o n c o e f f i c i e n t on DCS i n a l l admission equations remained i n s i g n i f i c a n t i n 1981/82. The o v e r a l l goodness of f i t f o r d i f f e r e n t equations d i d not change much i n 1971 and 1981/82, but improved c l e a r l y f o r s u r g i c a l equations i n 1976 i m p l y i n g t h a t t h e r e might be time-dependent f a c t o r s t h a t a l t e r the shape of the response of s u r g i c a l use to bed a v a i l a b i l i t y . In the pooled data the v a r i a t i o n of d i f f e r e n t measures of i n p a t i e n t use accounted f o r by the o v e r a l l model improved s l i g h t l y as expected. In g e n e r a l , the r e g r e s s i o n c o e f f i c i e n t s on DCS decreased s l i g h t l y but remained n e g a t i v e and s t a t i s t i c a l l y s i g n i f i c a n t . 4.6 Confounding f a c t o r s A c c o r d i n g t o Roemer's Law a v a i l a b i l i t y of p a e d i a t r i c beds was expected t o be a major confounding f a c t o r when s t u d y i n g the r e l a t i o n s h i p between DCS and p a e d i a t r i c i n p a t i e n t use. R e s u l t s i n i n d i v i d u a l years suggested t h a t t h i s r e a l l y c o u l d be the case. However, the p r o p o r t i o n of v a r i a n c e e x p l a i n e d by the models used was, i n g e n e r a l , lower than i n s i m i l a r s t u d i e s a t an a d u l t p o p u l a t i o n (Evans e t a 1 . f 1983), s u g g e s t i n g t h a t 175 t h e r e might be o t h e r important f a c t o r s a f f e c t i n g p a e d i a t r i c h o s p i t a l use. The e x p l o r a t i o n of the e f f e c t s of a d d i t i o n a l v a r i a b l e s , which may have i n f l u e n c e on day c a r e s u r g e r y a v a i l a b i l i t y , bed a v a i l a b i l i t y , and p a e d i a t r i c i n p a t i e n t use, and thus cause s y s t e m a t i c b i a s i n the r e l a t i o n s h i p , observed t o t h i s p o i n t , was the next s t e p i n t h i s study. 4.6.1 P h y s i c i a n - t o - p o p u l a t i o n r a t i o I f one hyp o t h e s i z e d t h a t p h y s i c i a n a v a i l a b i l i t y s n h s t i t u t e d f o r p a e d i a t r i c i n p a t i e n t care ( f o r any g i v e n bed stock) and t h a t when p h y s i c i a n s are abundant more surgery i s performed on a day care s u r g e r y b a s i s , then one would expect t o see a d e c l i n e i n i n p a t i e n t u t i l i z a t i o n c oncurrent w i t h an i n c r e a s e i n day care surgery. But, when p h y s i c i a n c a p a c i t y i s entered i n t o the equa t i o n , the a s s o c i a t i o n between day care surgery a v a i l a b i l i t y and i n p a t i e n t u t i l i z a t i o n should d i s a p p e a r c o m p l e t e l y o r be reduced i n s t r e n g t h . Increase i n p h y s i c i a n s u p p l y over time has o c c u r r e d c o n c u r r e n t l y w i t h i n c r e a s e i n DCS and decrease i n p a e d i a t r i c i n p a t i e n t u t i l i z a t i o n i n B.C., su g g e s t i n g t h a t t h i s hypothesis c o u l d be r e l e v a n t i n a n a l y z i n g the p o o l e d d a t a . On the oth e r hand, i t i s q u i t e c o n c e i v a b l e t h a t a h i g h l e v e l of p h y s i c i a n a v a i l a b i l i t y leads t o both h i g h l e v e l s of i n p a t i e n t a c t i v i t y , and ( f o r a g i v e n bed stock) i n c r e a s e d p r e s s u r e f o r day care surgery a c t i v i t y . T h i s d u a l p o s i t i v e e f f e c t , i f present and not accounted f o r , c o u l d mask a net n e g a t i v e e f f e c t from day care surgery t o i n p a t i e n t use. 176 In o t h e r words, i n the absence of p h y s i c i a n supp l y growth, p a e d i a t r i c i n p a t i e n t use might have f a l l e n f a s t e r and the ' t r u e ' day c a r e su r ge ry s u b s t i t u t i o n e f f e c t would have been ob se rved . F u r t h e r , a l a r g e and a c t i v e p h y s i c i a n p o p u l a t i o n c o u l d l e a d t o p r e s s u r e f o r more bed a v a i l a b i l i t y . A p o s i t i v e i n f l u e n c e of p h y s i c i a n s tock on both beds and i n p a t i e n t use c o u l d cause b i a s i n the observed bed a v a i l a b i l i t y e f f e c t , and i f not e x p l i c i t l y a d j u s t e d f o r , c o u l d l e a d t o i n a p p r o p r i a t e i n f e r e n c e of c a u s a l i t y from beds a l o n e . Thus, the a v a i l a b i l i t y o f p h y s i c i a n s t o the p a e d i a t r i c p o p u l a t i o n was e n t e r e d i n t o the r e g r e s s i o n equa t i ons as a p o s s i b l e con found ing f a c t o r . T h i s s tudy d i d not t r y t o e x p l o r e the r e l a t i o n s h i p between p h y s i c i a n a v a i l a b i l i t y and p a e d i a t r i c h o s p i t a l u t i l i z a t i o n i n any s p e c i f i c d e t a i l s i n c e the main focus was e l sewhere . The DOCS v a r i a b l e and d i f f e r e n t s p e c i a l t y s p e c i f i c p h y s i c i a n a v a i l a b i l i t y measures were o n l y i n t r o d u c e d f o r a d j u s t i n g p o s s i b l e con found ing e f f e c t s when a n a l y z i n g the e f f e c t of day c a r e s u r g e r y and bed a v a i l a b i l i t y on p a e d i a t r i c i n p a t i e n t use . Because F T E - a d j u s t e d p h y s i c i a n a v a i l a b i l i t y measures c o u l d not be c a l c u l a t e d p r i o r t o 1973, the i n d i v i d u a l y e a r equa t i on s a re p r e s e n t e d o n l y f o r the yea r s 1976 and 1981/82 and the poo led a n a l y s i s cover s the yea r s 1973-1976 and 1981/82-1982/83. T a b l e 22 shows the c o e f f i c i e n t s on DCS and BEDS a f t e r s t a n d a r d i z i n g f o r the e f f e c t of DOCS v a r i a b l e . S i nce DCS/BEDS Table 22 School District Inpatient Hospital Utilization Equations with DCS. BEDS. BEDSQ and DOCS in 1976. 1981/82 and Pooled 1973-1982/83 Dataset Admissions Year & Measure DCS SE BEDS SE BEDSQ SE DOCS SE CONST R2 SE Y 1976 1981/82 Pooled 1973-83 MEDS/SURG 0.22 0.53 29.753 6.99 -0.52 0.68 -0.25 0.33 37.15 0.6791 29.67 SURG -0.03 0.14 5.122 1.84 -0.351 0.18 0.14 0.09 19.24 0.1747 7.79 SURG-T&A 0.00 0.09 3.302 1.14 -0.231 0.11 0.13 0.05 13.26 0.2117 4.86 SURG A -0.02 0.12 3.881 1.55 -0.25 0.15 0.07 0.07 11.22 0.1365 6.59 SURG B -0.02 0.11 3.471 1.52 -0.26 0.15 0.11 0.07 8.36 0.0963 6.44 SURG C 0.00 0.04 1.141 0.51 -0.09 0.05 0.061 0.02 2.27 0.1161 2.17 MEDS/SURG -0.20 0.40 30.523 5.44 -1.201 0.53 0.421 0.18 8.42 0.7192 22.12 SURG -0.19 0.12 3.281 1.59 -0.12 0.16 0.08 0.05 23.56 0.3102 6.45 SURG-T&A -0.12 0.09 2.601 1.16 -0.08 0.11 0.06 0.04 17.27 0.3725 4.74 SURG A -0.11 0.09 2.311 1.21 -0.13 0.12 0.01 0.04 12.63 0.1554 4.90 SURG B -0.09 0.09 2.28 1.17 -0.17 0.11 0.00 0.04 11.77 0.0837 4.77 SURG C -0.03 0.04 1.05 0.55 -0.07 0.05 -0.02 0.02 4.18 0.0956 2.24 MED/SURG -0.17 0.22 33.943 3.15 -1.012 0.31 _ _ 28.04 0.6386 33.28 -0.19 0.22 33.873 3.16 -1.012 0.31 0.03 0.12 27.00 0.6378 33.31 SURG -0.182 0.06 6.043 0.91 -0.403 0.09 - - 26.00 0.2219 9.61 -0.183 0.07 6.043 0.91 -0.403 0.09 0.00 0.03 25.96 0.2202 9.62 SURG-T&A -0.06 0.04 3.823 0.54 -0.223 0.05 - - 18.24 0.2758 5.67 -0.091 0.04 3.663 0.53 -0.213 0.05 0.073 0.02 15.93 0.2945 5.60 SURG A -0.243 0.06 4.373 0.81 -0.293 0.08 - - 16.32 0.2018 8.53 -0.213 0.06 4.563 0.80 -0.303 0.08 -0.082 0.03 19.05 0.2138 8.47 SURG B -0.193 0.05 3.763 0.75 -0.283 0.07 - - 14.67 0.1377 7.97 -0.162 0.05 3.893 0.75 -0.293 0.07 -0.061 0.03 16.60 0.1443 7.94 SURG C -0.062 0.02 1.303 0.26 -0.103 0.03 - - 4.72 0.1305 2.77 -0.062 0.02 1.293 0.26 -0.103 0.03 0.00 0.01 4.68 0.1286 2.78 1 p < 0.05 2 p < 0.01 3 p < 0.001 . C o n t i n u e d Table 22 School District Inpatient Hospital Utilization Equations with DCS, BEDS. BEDSQ and DOCS in 1976, 1981/82 and Pooled 1973-1982/83 Dataset Days Year & Measure DCS SE BEDS SE BEDSQ SE DOCS SE CONST R2 SE Y 1976 1981/82 1973-83 MEDS/SURG 3.43 3.33 114.701 44.05 7.68 4.25 -5.441 2.06 352.73 0.7602 186.89 SURG -0.51 0.69 42.813 9.09 -3.063 0.88 -0.80 0.42 120.59 0.3514 38.57 SURG-T&A -0.28 0.70 37.883 9.20 -2.732 0.88 -0.73 0.43 103.35 0.2740 39.02 SURG A 0.09 0.38 12.651 5.02 -0.49 0.48 -0.37 0.23 46.24 0.2846 21.29 SURG B -0.23 0.26 6.79 3.41 -0.45 0.33 0.09 0.16 26.57 0.0940 14.46 SURG C -0.03 0.09 1.36 1.14 -0.06 0.11 0.10 0.05 7.87 0.0970 4.83 MEDS/SURG 3.60 1.95 148.813 26.68 -5.401 2.61 1.26 0.89 -46.15 0.7056 108.52 SURG -0.32 0.66 9.31 9.07 0.21 0.89 0.872 0.30 73.76 0.2925 36.90 SURG-T&A -0.06 0.65 7.84 8.86 0.33 0.87 0.832 0.30 58.73 0.2793 36.05 SURG A -0.36 0.22 2.60 2.95 0.26 0.29 0.07 0.10 31.19 0.3859 11.99 SURG B -0.331 0.17 2.55 2.26 -0.15 0.22 0.01 0.08 28.92 0.1045 9.20 SURG C -0.10 0.08 1.46 1.09 -0.08 0.11 -0.01 0.04 9.30 0.0866 4.43 MED/SURG -2.23 1.41 145.273 20.46 2.88 2.01 _ _ 171.46 0.6794 216.31 -1.14 1.44 150.873 20.31 2.57 1.99 -2.432 0.74 252.61 0.6863 213.97 SURG -0.851 0.36 30.853 5.27 -1.221 0.52 - - 111.78 0.3126 55.73 -0.761 0.37 31.333 5.29 -1.241 0.52 -0.21 0.19 118.73 0.3129 55.72 SURG-T&A -0.44 0.34 25.523 4.86 -0.80 0.48 - - 93.96 0.2968 51.34 -0.41 0.35 25.643 4.88 -0.81 0.48 -0.05 0.18 95.73 0.2954 51.39 SURG A -1.003 0.20 13.633 2.91 -0.49 0.29 - - 44.07 0.2991 30.80 -0.803 0.20 14.693 2.87 -0.55 0.28 -0.463 0.10 59.38 0.3268 30.18 SURG B -0.593 0.11 7.863 1.63 -0.563 0.16 - - 33.49 0.1837 17.23 -0.523 0.12 8.253 1.62 -0.583 0.16 -0.172 0.06 39.11 0.1966 17.10 SURG C -0.163 0.04 2.533 0.58 -0.162 0.06 - - 10.74 0.1608 6.08 -0.163 0.04 2.533 0.58 -0.162 0.06 0.00 1.02 10.73 0.1590 6.09 1 p < 0.05 2 p < 0.01 3 p < 0.001 179 model had not been p re sen ted p r e v i o u s l y w i t h the poo led 1973-1982/83 d a t a , these r e g r e s s i o n equa t i ons were c a l c u l a t e d f o r compar i son i n T a b l e 22. I n c l u s i o n of a s i n g l e p h y s i c i a n a v a i l a b i l i t y measure (DOCS) improved the goodness of f i t o f the o v e r a l l r e g r e s s i o n e q u a t i o n f o r SURG-T&A and SURG-C types o f admis s ions i n 1976, but d i d not have any e f f e c t on the f i t i n 1981/82 and i n the p o o l e d 1973-1982/83 d a t a s e t (Tab les 21 and 22) . The c o e f f i c i e n t s on BEDS and BEDS 2 remained p r a c t i c a l l y the same i n d i f f e r e n t i n p a t i e n t admis s ion equa t i ons and changed o n l y s l i g h t l y i n p a t i e n t day equat ions a f t e r adjustment f o r p h y s i c i a n a v a i l a b i l i t y . T h i s c o n s i s t e n c y i n bed a v a i l a b i l i t y e f f e c t suggests t h a t Roemer e f f e c t i s r e l a t i v e l y independent of the o v e r a l l p h y s i c i a n supp l y . A l s o the e f f e c t of adjustment f o r p h y s i c i a n a v a i l a b i l i t y on the r e l a t i o n s h i p between day c a r e s u r g e r y a v a i l a b i l i t y and i n p a t i e n t u t i l i z a t i o n was o n l y m a r g i n a l i n a l l e q u a t i o n s . The impact o f DCS on t o t a l and s u r g i c a l admis s ions remained low and s t a t i s t i c a l l y i n s i g n i f i c a n t i n 1976 and 1981/82. In the poo led d a t a s e t the a s s o c i a t i o n between DCS and o v e r a l l s u r g i c a l u t i l i z a t i o n remained n e g a t i v e and s t a t i s t i c a l l y s i g n i f i c a n t . Thus, o v e r a l l p h y s i c i a n a v a i l a b i l i t y t o the p a e d i a t r i c p o p u l a t i o n was not a c r i t i c a l con found ing v a r i a b l e i n examining the r e l a t i o n s h i p s between day ca re su r ge ry a v a i l a b i l i t y , bed supp l y and p a e d i a t r i c i n p a t i e n t u t i l i z a t i o n . 180 The next s t e p was t o i n c l u d e the more r e f i n e d measures of p h y s i c i a n stock i n the r e g r e s s i o n equations i n the pooled 1973-1982/83 d a t a s e t (Table 23). One can hyp o t h e s i z e t h a t a v a i l a b i l i t y of d i f f e r e n t p h y s i c i a n s p e c i a l t i e s have d i f f e r e n t e f f e c t s on p a e d i a t r i c i n p a t i e n t u t i l i z a t i o n . A l a r g e surgeon p o p u l a t i o n c o u l d l e a d t o more i n p a t i e n t s u r g e r y and ( f o r a g i v e n bed stock) t o i n c r e a s e d p r e s s u r e f o r day care surgery a c t i v i t y , o b s c u r i n g the "tru e " s u b s t i t u t i o n e f f e c t from DCS un l e s s surgeon a v a i l a b i l i t y i s accounted f o r . Other p h y s i c i a n s p e c i a l t i e s may not have s i m i l a r e f f e c t s , and thus the mix of d i f f e r e n t s p e c i a l t i e s i n a sch o o l d i s t r i c t c o u l d be more important than o v e r a l l p h y s i c i a n a v a i l a b i l i t y i n confounding the r e l a t i o n s h i p between day care surgery and p a e d i a t r i c i n p a t i e n t use. The simultaneous adjustment f o r GP, PAED, SURGEON, ANA and OTHER measures of p h y s i c i a n a v a i l a b i l i t y improved the o v e r a l l f i t of a l l i n p a t i e n t u t i l i z a t i o n equations f o r both admissions and p a t i e n t days (Tables 22 and 23). T h i s adjustment a f f e c t e d a l s o the a s s o c i a t i o n s between DCS, BEDS and i n p a t i e n t u t i l i z a t i o n . Compared t o the c o e f f i c i e n t s on DCS i n DCS/BEDS model i n Tab l e 22, the corresponding c o e f f i c i e n t s i n Table 23 were g e n e r a l l y s m a l l e r (and i n many cases, l e s s s i g n i f i c a n t ) , e s p e c i a l l y f o r m e d i c a l / s u r g i c a l admissions. The r e g r e s s i o n c o e f f i c i e n t i n the o v e r a l l s u r g i c a l e quation i m p l i e d t h a t 100 day care s u r g e r y cases would have saved 15 s u r g i c a l i n p a t i e n t admissions w i t h average l e n g t h of s t a y of 3.4 days. The Table 23 School District Inpatient Hospital Utilization Equations with DCS, BEDS, BEDSQ, GP. PAED, SURGEON, ANA and OTHER Variables in Pooled 1973-1982/83 Dataset Variables MED/SURG Admissions SURG SURG-T&A SURG A SURG B SURG C MED/SURG Days SURG SURG-T&A SURG A SURG B SURG C DCS -0.04 -0.151 -0.07 -0.192 -0.152 -0.052 -2.31 -0.51 -0.18 -0.682 -0.483 -0.143 SE 0.23 0.07 0.04 0.06 0.05 0.02 2.67 0.38 0.35 0.21 0.12 0.04 BEDS 33.693 6.243 3.793 4.733 4.063 1.403 151.213 32.293 26.403 15.263 8.683 2.803 SE 3.12 0.91 0.51 0.80 0.75 0.26 20.10 5.22 4.79 2.86 1.62 0.56 BEDSQ -1.073 -0.423 -0.223 -0.313 -O.303 -0.103 2.16 -1.362 -0.90 -0.631 -0.623 -0.182 SE 0.31 0.09 0.05 0.08 0.07 0.03 1.97 0.51 0.47 0.28 0.16 0.06 GP -0.38 -0.07 -0.04 -0.10 -0.05 -0.02 -4.643 -1.002 -0.972 -0.592 -0.14 -0.05 SE 0.20 0.06 0.03 0.05 0.05 0.02 1.31 0.34 0.31 0.19 0.11 0.04 PAED -2.84 -1.582 -0.771 -1.472 -1.292 -0.492 -26.891 -6.561 -4.50 -4.712 -3.192 -1.203 SE 1.88 0.55 0.31 0.48 0.46 0.16 12.13 3.15 2.89 1.73 0.98 0.34 SURGEON -0.16 0.301 0.433 0.09 0.08 0.163 -2.31 1.721 2.052 -0.14 0.12 0.383 SE 0.41 0.12 0.07 0.11 0.10 0.03 2.67 0.69 0.64 0.38 0.22 0.07 ANA 2.301 0.10 -0.08 0.13 0.07 -0.17 10.37 -1.54 -2.07 -0.38 0.06 -0.461 SE 1.10 0.32 0.18 0.28 0.27 0.09 7.06 1.84 1.68 1.01 0.57 0.20 OTHER 0.562 0.02 0.07 -0.08 -0.06 -0.02 0.39 0.16 0.28 -0.21 -0.16 -0.03 SE 0.21 0.06 0.04 0.06 0.05 0.02 1.37 0.36 0.33 0.20 0.11 0.04 CONST 37.69 26.04 16.18 18.84 16.08 4.14 305.85 123.79 101.61 60.72 37.60 9.56 RSQ 0.6527 0.2417 0.3555 0.2265 0.1531 0.1858 0.6968 0.3391 0.3303 0.3367 0.2085 0.2279 SE Y 32.62 9.49 5.35 8.40 7.89 2.68 210.35 54.64 50.11 29.96 16.97 5.84 1 p < 0.05 2 p < 0.01 3 p < 0.001 182 adjustment f o r d i f f e r e n t s p e c i a l t y measures i n c r e a s e d the s t r e n g t h of a s s o c i a t i o n between bed a v a i l a b i l i t y and i n p a t i e n t u t i l i z a t i o n , w i t h the e x c e p t i o n of MED/SURG, SURG and SURG-T&A equa t i on s f o r admi s s i on s . I t i s p o s s i b l e t h a t a v a i l a b i l i t y of some p h y s i c i a n s p e c i a l t i e s ( e . g . , p a e d i a t r i c i a n s ) l eads to more ambula tory c a re and l e s s p a e d i a t r i c i n p a t i e n t c a r e ( i n p a r t i c u l a r l y , day ca re s u r g e r y - t y p e ) , but the se s p e c i a l t i e s a re s t i l l p o s i t i v e l y a s s o c i a t e d w i t h p a e d i a t r i c bed a v a i l a b i l i t y i n a s c h o o l d i s t r i c t . Adjustment f o r these s p e c i a l t i e s , as i n T a b l e 23, i s expected t o r e v e a l h i g h e r bed s u p p l y e f f e c t . A l though the changes caused by the adjustment f o r a v a i l a b i l i t y of d i f f e r e n t p h y s i c i a n s p e c i a l t i e s d i d not r a d i c a l l y a l t e r the a s s o c i a t i o n s t h a t had been r e v e a l e d e a r l i e r , t hey suppor t the p l a u s i b i l i t y of a c a u s a l a s s o c i a t i o n between bed supp l y and p a e d i a t r i c i n p a t i e n t u t i l i z a t i o n . The r e s u l t s a l s o suppor t the p r e v i o u s f i n d i n g s t h a t DCS has not had any independent impact on o v e r a l l i n p a t i e n t u t i l i z a t i o n , but a s i g n i f i c a n t e f f e c t on c e r t a i n c a t e g o r i e s of s u r g i c a l u t i l i z a t i o n . 4 .6 .2 Soc ioeconomic v a r i a b l e s These v a r i a b l e s were i n c l u d e d i n the s tudy as a p roxy f o r h o s p i t a l c a r e need. The e f f e c t o f these v a r i a b l e s a l one on p a e d i a t r i c i n p a t i e n t u t i l i z a t i o n was ana l y zed f i r s t (Tab le 24) . A l t o g e t h e r these v a r i a b l e s e x p l a i n e d h a l f of the v a r i a t i o n i n m e d i c a l / s u r g i c a l admis s ion r a t e s i n 1971, 1981 Table 24 School District Inpatient Hospital Utilization Equations with Socioeconomic Variables in 1971, 1981/82 and Pooled 1968-1982/83 Dataset Year & Measure CAN SE MTENG SE IND SE RURAL SE EDUC SE ROOMS SE Admissions: 1971 MED/SURG 0.13 1.51 SURG -0.39 0.31 SURG-T&A -0.16 0.23 SURG A -0.17 0.29 SURG B -0.28 0.27 SURG C -0.03 0.09 1981/82 MED/SURG 2.041 0.98 SURG 0.461 0.13 SURG-T&A 0.381 0.17 SURG A 0.20 0.16 SURG B 0.13 0.16 SURG C 0.01 0.08 Pooled MED/SURG 1.433 0.38 1968-83 SURG 0.06 0.11 SURG-T&A -0.01 0.06 SURG A 0.13 0.10 SURG B 0.07 0.09 SURG C -0.01 0.02 2.47 1.54 4.513 1.11 -0.14 0.52 0.31 -0.08 0.22 -0.121 0.25 0.23 0.23 0.16 -0.06 0.38 0.29 -0.03 0.21 -0.10 0.37 0.28 -0.12 0.20 -0.09 0.02 0.10 0.04 0.07 -0.03 0.55 1.08 3.103 0.62 0.03 -0.39 0.23 0.462 0.13 -0.01 -0.27 0.18 0.332 0.10 0.01 -0.14 0.18 0.282 0.10 -0.02 -0.16 0.17 0.201 0.10 -0.02 0.03 0.08 0.05 0.05 -0.02 0.18 0.25 4.193 0.29 -0.07 0.12 0.07 0.181 0.08 -0.072 O.U 2 0.04 0.283 0.05 -O.031 0.05 0.07 0.10 0.08 -0.073 0.07 0.06 0.01 0.07 -0.073 0.042 0.02 0.063 0.02 -0.023 0.27 6.02 4.13 -48.201 18.53 0.05 1.40 0.84 1.98 3.75 0.04 0.55 0.62 -0.51 2.76 0.05 1.15 0.79 1.29 3.53 0.05 0.97 0.74 2.82 3.32 0.02 -0.02 0.26 0.92 1.15 0.20 2.32 1.74 -26.531 10.57 0.04 -0.30 0.38 -5.981 2.28 0.03 -0.34 0.29 -4.892 1.79 0.03 -0.12 0.28 -3.17 1.72 0.03 -0.16 0.28 -2.75 1.67 0.02 -0.05 0.13 -1.06 0.81 0.08 _ -53.013 4.36 0.02 - - -9.313 1.29 0.01 - - -3.763 0.69 0.02 - - -9.843 1.14 0.02 - - -7.573 1.03 0.00 - - -0.802 0.27 CO Continued Table 24 School District Inpatient Hospital Utilization Equations with Socioeconomic Variables in 1971. 1981/82 and Pooled 1968-1982/83 Dataset Year & Measure INC SE UNEM SE WHITE SE PRIM SE CONST R2 SE Y Admissions: 1971 MED/SURG -0.01 0.01 -4.34 3.61 -1.36 0.99 -1.46 0.75 279.92 0.4836 45.64 SURG -0.00 0.00 0.19 0.73 -0.511 0.20 -0.16 0.15 56.14 0.0450 9.23 SURG-T&A -0.00 0.00 -0.60 0.54 -0.08 0.15 -0.09 0.11 49.13 0.0012 6.80 SURG A -0.00 0.00 0.28 0.69 -0.36 0.19 -0.17 0.14 30.60 0.0021 8.71 SURG B -0.00 0.00 0.25 0.65 -0.381 0.18 -0.14 0.13 30.66 0.0179 8.17 SURG C -0.002 0.00 -0.36 0.22 0.08 0.06 0.00 0.05 15.54 0.0423 2.82 1981/82 MED/SURG 0.00 0.00 -2.51 2.40 -0.63 0.64 -0.70 0.57 -23.05 0.5034 29.41 SURG 0.00 0.00 0.16 0.52 -0.17 0.14 -0.14 0.12 59.42 0.3334 6.34 SURG-T&A 0.00 0.00 0.31 0.41 -0.14 0.11 -0.201 0.10 47.32 0.3102 4.97 SURG A 0.00 0.00 0.21 0.39 -0.11 0.10 -0.09 0.09 26.10 0.1968 4.78 SURG B 0.00 0.00 0.24 0.38 -0.14 0.10 -0.06 0.09 31.90 0.1316 4.65 SURG C 0.00 0.00 0.24 0.18 -0.09 0.05 -0.07 0.04 7.50 0.0773 2.27 Pooled MED/SURG 0.002 0.00 -4.093 0.90 -0.14 0.23 -0.662 0.21 357.44 0.5017 43.45 1968-83 SURG -0.003 0.00 0.13 0.27 0.192 0.07 -0.05 0.06 90.33 0.1534 12.86 SURG-T&A -0.003 0.00 0.07 0.14 0.06 0.04 -0.071 0.03 47.44 0.1380 6.91 SURG A -0.003 0.00 -0.12 0.24 0.273 0.06 -0.03 0.06 74.92 0.1895 11.40 SURG B -0.003 0.00 0.09 0.21 O.203 0.05 -0.03 0.05 62.55 0.1569 10.28 SURG C -0.003 0.00 -0.01 0.06 0.063 0.01 -0.02 0.01 11.80 0.1361 2.70 1 p < 0.05 2 p < 0.01 3 p < 0.001 .Continued Table 24 School District Inpatient Hospital Utilization Equations with Socioeconomic Variables in 1971. 1981/82 and Pooled 1968-1982/83 Dataset Year & Measure CAN SE MTENG SE IND SE RURAL SE EDUC SE ROOMS SE Days: 1971 MED/SURG 2.08 10.63 5.29 10.82 39.433 7.75 0.68 1.88 27.17 28.98 -428.282 130.00 SURG -0.04 1.96 0.88 1.99 1.82 1.43 -0.31 0.35 3.14 5.33 -41.69 23.92 SURG-T&A 0.31 1.93 0.39 1.96 2.34 1.41 -0.21 0.34 1.76 5.26 -42.97 23.59 SURG A 0.97 0.94 0.13 0.96 0.73 0.69 -0.19 0.17 1.44 2.56 -15.02 11.50 SURG B -0.39 0.60 0.45 0.61 -0.02 0.44 -0.18 0.11 1.04 1.63 5.66 7.31 SURG C -0.03 0.20 -0.03 0.21 0.29 0.15 -0.06 0.04 -0.28 0.56 2.92 2.50 1981/82 MED/SURG 4.74 5.06 4.33 5.55 16.803 3.19 -0.14 1.02 11.03 8.97 -104.12 54.37 SURG 1.54 1.27 -0.83 1.39 2.142 0.80 0.19 0.26 0.21 2.25 -37.032 13.66 SURG-T&A 1.32 1.28 -0.49 1.40 1.871 0.81 0.20 0.26 0.25 2.27 -33.801 13.74 SURG A 1.071 0.43 -0.51 0.47 0.993 0.27 0.02 0.09 -0.33 0.76 -10.791 4.59 SURG B 0.38 0.30 -0.46 0.33 0.31 0.19 -0.03 0.06 -0.47 0.53 -6.501 3.20 SURG C 0.07 0.15 -0.03 0.17 0.07 0.10 -0.04 0.03 -0.24 0.27 -2.01 1.63 Pooled MED/SURG 7.021 2.81 -5.392 1.88 34.413 2.13 0.22 0.57 _ _ -424.023 32.38 1968-83 SURG 0.76 0.64 -0.22 0.43 2.753 0.48 -0.17 0.13 - - -70.093 7.36 SURG-T&A 0.65 0.55 -0.17 0.37 2.973 0.41 -0.13 0.11 - - -53.923 6.31 SURG A 0.891 0.36 -0.12 0.24 1.023 0.27 -0.151 0.07 - - -45.413 4.11 SURG B 0.15 0.20 0.11 0.13 0.01 0.15 -0.112 0.04 - - -19.713 2.33 SURG C -0.01 0.05 0.102 0.04 0.183 0.04 -0.043 0.01 - - -2.453 0.62 CO . . . C o n t i n u e d Table 24 School District Inpatient Hospital Utilization Equations with Socioeconomic Variables in 1971. 1981/82 and Pooled 1968-1982/83 Dataset Year & Measure INC SE UNEM SE WHITE SE PRIM SE CONST R2 SE Y Days: 1971 MED/SURG 0.02 0.10 -39.07 25.35 -4.16 6.94 -7.73 5.28 2750.58 0.5873 320.22 SURG 0.01 0.02 -8.47 4.66 -1.59 1.28 -0.40 0.97 490.45 0.2261 58.91 SURG-T&A 0.00 0.02 -10.921 4.60 -0.57 1.26 -0.31 0.96 468.24 0.2408 58.10 SURG A 0.00 0.01 -0.66 2.24 -0.63 0.61 -0.65 0.47 127.75 0.0943 28.33 SURG B -0.00 0.00 1.03 1.43 -0.831 0.39 -0.17 0.30 72.64 -0.0234 18.00 SURG C -0.012 0.00 -0.69 0.49 0.17 0.13 -0.04 0.10 31.81 0.0473 6.15 1981/82 MEO/SURG 0.02 0.02 -12.94 12.35 -3.84 3.27 -4.37 2.91 107.65 0.4280 151.27 SURG 0.01 0.01 2.19 3.10 -0.03 0.82 -0.60 0.73 196.73 0.2500 37.99 SURG-T&A 0.01 0.01 2.62 3.12 0.06 0.83 -0.76 0.74 160.29 0.1892 38.24 SURG A 0.00 0.00 0.29 1.04 0.12 0.28 -0.16 0.25 36.12 0.3022 12.78 SURG B 0.00 0.00 0.45 0.73 -0.22 0.19 0.01 0.17 70.62 0.1634 8.90 SURG C 0.00 0.00 0.67 0.37 -0.14 0.10 -0.09 0.09 20.44 0.0371 4.55 Pooled MED/SURG -0.032 0.01 -41.373 6.70 4.622 1.70 -2.15 1.59 3187.74 0.5457 323.07 1968-83 SURG -O.Ol2 0.00 -4.192 1.52 1.293 0.39 0.15 0.36 583.87 0.2450 73.47 SURG-T&A -O.Ol2 0.00 -4.042 1.30 0.982 0.33 0.01 0.31 467.12 0.2453 62.91 SURG A -O.Ol3 0.00 -2.983 0.85 1.073 0.22 -0.06 0.20 294.66 0.2623 41.03 SURG B -0.003 0.00 -0.21 0.48 0.473 0.12 -0.02 0.11 153.80 0.1657 23.22 SURG C -0.003 0.00 -0.19 0.13 0.173 0.03 -0.06 0.03 30.46 0.1607 6.22 1 p < 0.05 2 p < 0.01 3 p < 0.001 187 and i n the p o o l e d da ta s e t . Fo r h o s p i t a l day s , the e x p l a i n e d p r o p o r t i o n of v a r i a n c e was 59 p e r c e n t i n 1971, 43 p e r c e n t i n 1981 and 56 p e r c e n t i n the poo led d a t a . The percentage of p o p u l a t i o n t h a t i s of Ind ian o r Eskimo e t h n i c i t y and the average number of rooms per d w e l l i n g were the most power fu l de te rminant s of p a e d i a t r i c admiss ions and h o s p i t a l days . The h i g h e r the p r o p o r t i o n of Ind ians o r Eskimos i n the p o p u l a t i o n the h i g h e r the p a e d i a t r i c h o s p i t a l u t i l i z a t i o n . The number of rooms per d w e l l i n g was n e g a t i v e l y r e l a t e d to h o s p i t a l u t i l i z a t i o n . The p r o p o r t i o n of v a r i a n c e i n t o t a l s u r g i c a l i n p a t i e n t use accounted f o r by the soc ioeconomic v a r i a b l e s was 15 - 30 p e r c e n t , except f o r admiss ions i n 1971 when i t was l e s s than f i v e p e r c e n t . In the poo led d a t a s e t the ROOMS v a r i a b l e had the h i g h e s t a s s o c i a t i o n w i t h s u r g i c a l u t i l i z a t i o n . The r e s u l t s i n T a b l e 24 r a i s e the p o s s i b i l i t y t h a t soc ioeconomic c h a r a c t e r i s t i c s , as a p roxy f o r h o s p i t a l c a re needs , might be p r imary determinant s of d i f f e r e n c e s i n use and t h e r e b y of h o s p i t a l c a p a c i t y . I f p a e d i a t r i c bed a v a i l a b i l i t y was m a i n l y determined by needs, which a l s o then determined u se , then one may a n t i c i p a t e t h a t i n c l u s i o n of the bed supp ly measures i n the equa t i on w i th v a r i a b l e s t h a t c a p t u r e the e f f e c t of need would not add any th ing t o the goodness of f i t f o r the o v e r a l l e q u a t i o n , and the BED v a r i a b l e would not have s i g n i f i c a n t r e g r e s s i o n c o e f f i c i e n t . 188 T a b l e 25 shows t h a t add ing bed c a p a c i t y and day c a r e su r ge ry a v a i l a b i l i t y t o the soc ioeconomic v a r i a b l e equa t i on s s u b s t a n t i a l l y improves the goodness o f f i t of a l l the admi s s i on and h o s p i t a l day equa t i ons i n 1971 and 1981/82 and the p o o l e d e q u a t i o n s , the o n l y e x c e p t i o n be ing SURG B u t i l i z a t i o n i n 1981/82. As p r e v i o u s ana l y se s have shown, DCS has no e f f e c t on the goodness of f i t of these e q u a t i o n s ; the improvement i s due to the BEDS v a r i a b l e a l o n e . In the poo led da ta s e t i n T a b l e 25, 67 p e r c e n t of v a r i a n c e i n m e d i c a l / s u r g i c a l days i s accounted f o r , compared t o 55 p e r c e n t f o r soc ioeconomic v a r i a b l e s a l one (Tab le 24) . On the o t h e r hand, comparing T a b l e 25 t o Tab le 20, the net c o n t r i b u t i o n of soc ioeconomic v a r i a b l e s when added t o an e q u a t i o n a l r e a d y c o n t a i n i n g BEDS i s much s m a l l e r . An improvement o f 7 pe rcen tage p o i n t s , from 57 p e r c e n t i n T a b l e 20 t o 64 p e r c e n t i n T a b l e 25 i n d i c a t e s t h a t soc ioeconomic v a r i a b l e s e x p l a i n e d 16 p e r c e n t (7/43) of the rema in ing unexp l a i ned v a r i a n c e i n m e d i c a l / s u r g i c a l admiss ions a f t e r adjustment f o r BEDS. , Bed c a p a c i t y , on the o t h e r hand, e x p l a i n e d 28 p e r c e n t (14/50) of the v a r i a n c e l e f t unexp l a ined by soc ioeconomic v a r i a b l e s . However, f o r p a t i e n t days the net c o n t r i b u t i o n s d i d not d i f f e r so much (26.7 p e r c e n t f o r beds and 23.3 p e r c e n t f o r soc ioeconomic v a r i a b l e s ) . These r e s u l t s suppor t the hypo the s i s t h a t p a e d i a t r i c bed a v a i l a b i l i t y e x e r t s a s i g n i f i c a n t i n f l u e n c e on p a e d i a t r i c i n p a t i e n t use independent of soc ioeconomic c h a r a c t e r i s t i c s . Table 25 School District Inpatient Hospital Utilization Equations with DCS. BEDS. BEDSQ and Socioeconomic Variables in 1971. 1981/82 and Pooled 1968-1982/83 Dataset Year & Measure DCS SE BEDS SE BEDSQ SE CAN SE MTENG SE Admissions: 1971 MED/SURG 0.21 0.58 28.842 9.89 -0.62 0.77 0.04 1.29 0.97 1.35 SURG -0.25 0.13 3.10 2.26 -0.11 0.18 -0.35 0.30 0.44 0.31 SURG-T&A -0.02 0.09 5.253 1.46 -0.18 0.11 -0.17 0.19 0.04 0.20 SURG A -0.331 0.12 0.08 2.13 0.07 0.17 -0.13 0.28 0.39 0.29 SURG B -0.291 0.12 -0.35 2.03 0.05 0.16 -0.24 0.27 0.41 0.28 SURG C -0.04 0.04 1.28 0.70 -0.06 0.05 -0.03 0.09 -0.02 0.10 1981/82 MED/SURG 0.45 0.41 24.863 5.19 -1.041 0.49 1.37 0.71 0.20 0.78 SURG -0.03 0.13 2.22 1.62 -0.08 0.15 0.35 0.22 -0.36 0.24 SURG-T&A -0.03 0.09 1.91 1.20 -0.04 0.11 0.26 0.16 -0.25 0.18 SURG A -0.07 0.10 1.38 1.26 -0.08 0.12 0.12 0.17 -0.08 0.19 SURG B -0.05 0.10 1.49 1.24 -0.12 0.12 0.08 0.17 -0.12 0.19 SURG C -0.08 0.04 0.82 0.57 -0.05 0.05 -0.06 0.08 0.09 0.09 Pooled KED/SURG -0.351 0.17 26.893 2.70 -0.873 0.25 0.872 0.32 0.36 0.22 1968-83 SURG -0.563 0.05 5.173 0.87 -0.353 0.08 -0.03 0.10 0.28 0.07 SURG-T&A -0.183 0.03 3.893 0.46 -0.213 0.04 -0.08 0.06 0.173 0.04 SURG A -0.583 0.05 3.283 0.76 -0.222 0.07 0.06 0.09 0.213 0.06 SURG B -0.493 0.04 2.643 0.70 -0.192 0.06 0.02 0.08 0.213 0.06 SURG C -0.063 0.01 1.323 0.19 -0.093 0.02 -0.03 0.02 0.063 0.02 .Continued Table 25 School District Inpatient Hospital Utilization Equations with DCS. BEDS, BEDSQ and Socioeconomic Variables in 1971. 1981/82 and Pooled 1968-1982/83 Dataset Year & Measure IND SE RURAL SE EDUC SE ROOMS SE Admissions: 1971 MED/SURG 0.70 1.23 -0.19 0.23 2.19 3.59 -23.86 16.68 SURG -0.42 0.28 -0.10 0.05 1.10 0.82 3.81 3.81 SURG-T&A -0.31 0.18 -0.06 0.03 -0.02 0.53 3.36 2.46 SURG A -0.24 0.27 -0.08 0.05 1.09 0.77 1.22 3.59 SURG B -0.19 0.25 -0.07 0.05 1.00 0.74 2.25 3.43 SURG C -0.06 0.09 -0.03 0.02 -0.13 0.25 1.69 1.18 1981/82 MED/SURG 1.693 0.44 -0.05 0.14 1.43 1.17 -10.11 7.30 SURG 0.321 0.14 -0.02 0.04 -0.37 0.36 -4.30 2.28 SURG-T&A 0.19 0.10 -0.01 0.10 -0.41 0.27 -3.12 0.17 SURG A 0.221 0.11 -0.04 0.03 -0.13 0.28 -2.35 1.78 SURG B 0.17 0.11 -0.04 0.03 -0.17 0.28 -2.29 1.74 SURG C 0.01 0.05 -0.041 0.02 -0.06 0.13 -0.47 0.80 Pooled MED/SURG 1.443 0.29 -0.10 0.06 _ _ -35.313 3.88 1968-83 SURG -0.08 0.09 -0.083 0.02 - - -4.603 1.24 SURG-T&A 0.01 0.05 -0.032 0.01 - - -1.07 0.66 SURG A -0.08 0.08 -0.073 0.02 - - -5.843 1.09 SURG B -0.11 0.07 -0.073 0.02 - - -4.293 1.00 SURG C 0.00 0.02 -0.023 0.00 - - 0.02 0.27 O . .Continued Table 25 School District Inpatient Hospital Utilization Equations with DCS. BEDS. BEDSQ and Socioeconomic Variables in 1971, 1981/82 and Pooled 1968-1982/83 Dataset Year & Measure INC SE UNEM SE WHITE SE PRIM SE CONST R2 SE Y Admissions: 1971 MED/SURG 0.00 0.01 0.16 3.20 -1.33 0.85 -1.14 0.66 145.18 0.6269 38.80 SURG -0.00 0.00 0.67 0.73 -0.501 0.19 . -0.19 0.15 38.27 0.1182 8.87 SURG-T&A -0.00 0.00 0.07 0.47 -0.07 0.13 -0.06 0.10 24.47 0.2955 5.71 SURG A -0.00 0.00 0.59 0.69 -0.391 0.18 -0.22 0.14 24.82 0.0813 8.35 SURG B -0.00 0.00 0.41 0.66 -0.391 0.18 -0.20 0.14 27.78 0.0666 7.97 SURG C -0.001 0.00 -0.22 0.23 0.08 0.06 -0.01 0.05 9.17 0.0955 2.74 1981/82 MED/SURG 0.00 0.00 -2.23 1.63 -0.21 0.43 -0.14 0.39 -66.67 0.7797 19.59 SURG 0.00 0.00 0.23 0.51 -0.13 0.14 -0.10 0.12 56.41 0.3821 6.10 SURG-T&A 0.00 0.00 0.40 0.38 -0.11 0.10 -0.15 0.09 45.00 0.4274 4.53 SURG A 0.00 0.00 0.26 0.40 -0.09 0.11 -0.07 0.09 24.55 0.2025 4.76 SURG B 0.00 0.00 0.24 0.39 -0.11 0.10 -0.04 0.09 29.67 0.1206 4.68 SURG C 0.00 0.00 0.30 0.18 -0.08 0.05 -0.06 0.04 7.00 0.1639 2.16 Pooled MED/SURG -0.003 0.00 -2.57 3 0.77 -0.15 0.20 -0.643 0.18 204.59 0.6444 . 36.70 1968-83 SURG -0.003 0.00 0.30 0.07 0.11 0.06 -0.131 0.06 56.80 0.2932 11.75 SURG-T&A -0.003 0.00 0.22 0.13 0.04 0.03 -0.102 0.03 25.72 0.2858 6.29 SURG A -0.003 0.00 0.02 0.22 0.183 0.06 -0.121 0.05 48.67 0.3339 10.34 SURG B -0.003 0.00 0.19 0.20 0.121 0.05 -O. l l 1 0.05 41.28 0.2886 9.44 SURG C -0.003 0.00 0.03 ' 0.05 0.063 0.01 -0.031 0.01 5.07 0.2230 6.55 1 p < 0.05 2 p < 0.01 3 p < 0.001 .Continued Table 25 School District Inpatient Hospital Utilization Equations with DCS, BEDS, BEDSQ and Socioeconomic Variables in 1971. 1981/82 and Pooled 1968-1982/83 Dataset Year & Measure DCS SE BEDS SE BEDSQ SE CAN SE MTENG SE Days: 1971 MED/SURG 2.34 3.85 SURG -0.05 0.80 SURG-T&A 0.56 0.77 SURG A -0.971 0.41 SURG B -0.621 0.26 SURG C -0.04 0.09 1981/82 MED/SURG 6.292 1.98 SURG 1.04 0.76 SURG-T&A 1.12 0.76 SURG A -0.19 0.24 SURG B -0.22 0.19 SURG C -0.181 0.09 Pooled MED/SURG -3.452 1.26 1968-83 SURG -2.453 0.32 SURG-T&A -1.413 0.27 SURG A -1.923 0.17 SURG B -1.223 0.10 SURG C -0.173 0.03 327.953 65.69 -15.442 5.10 52.023 13.72 -3.172 1.07 54.803 13.20 -3.272 1.03 5.14 6.91 -0.04 0.54 -0.16 4.49 0.06 0.35 2.07 1.55 -0.07 0.12 118.823 25.32 -4.29 2.40 2.45 9.75 0.45 0.92 1.96 9.74 0.54 0.92 0.50 3,06 0.33 0.29 1.00 2.38 -0.06 0.22 1.21 1.14 -0.04 0.11 166.483 20.21 -3.23 1.83 31.043 5.04 -1.833 0.46 27.253 4.38 -1.483 0.40 12.193 2.76 -0.712 0.25 5.293 1.55 -0.351 0.14 2.533 0.43 -0.153 0.04 1.56 8.58 -5.70 8.94 -0.02 1.79 -0.27 1.87 0.23 1.72 -0.99 1.80 1.11 0.90 0.00 0.94 -0.30 0.59 0.53 0.61 -0.02 0.20 -0.11 0.21 3.53 3.44 -0.40 3.80 1.70 1.33 -1.62 1.46 1.49 1.32 -1.33 1.46 0.70 0.42 -0.38 0.46 0.22 0.32 -0.30 0.36 -0.09 0.16 0.10 0.17 3.11 2.40 -3.861 1.63 0.18 0.60 0.51 0.41 0.15 0.52 0.29 0.35 0.63 0.33 0.42 0.22 0.02 0.18 0.443 0.12 -0.05 0.05 0.153 0.03 . Cont i nued Table 25 School District Inpatient Hospital Utilization Equations with DCS, BEDS, BEDSQ and Socioeconomic Variables in 1971, 1981/82 and Pooled 1968-1982/83 Dataset Year & Measure IND SE RURAL SE EDUC SE ROOMS SE Days: 1971 MED/SURG 16.561 8.19 0.21 SURG -0.10 1.71 -0.36 SURG-T&A 0.22 1.65 -0.30 SURG A -0.21 0.86 -0.14 SURG B -0.20 0.56 -0.15 SURG C 0.07 0.19 -0.06 1981/82 MED/SURG 9.703 2.15 0.04 SURG 1.60 0.83 0.30 SURG-T&A 1.30 0.83 0.32 SURG A 0.661 0.26 -0.03 SURG B 0.26 0.20 -0.07 SURG C -0.02 0.10 -O.071 Pooled MED/SURG 13.713 2.17 -0.04 1968-83 SURG 0.85 0.54 -0.21 SURG-T&A 1.131 0.47 -0.16 SURG A 0.20 0.30 -0.171 SURG B -0.30 0.17 -0.122 SURG C 0.02 0.05 -0.043 1.53 -2.38 23.85 -209.55 110.85 0.32 -0.28 4.98 -12.72 23.15 0.31 -2.07 4.79 -10.86 22.28 0.16 0.84 2.51 -12.11 11.66 0.10 1.08 1.63 4.77 7.58 0.04 -0.50 0.56 4.38 2.62 0.70 5.62 5.70 -25.80 35.61 0.27 -0.33 2.19 -31.441 13.72 0.27 -0.32 2.19 -27.961 13.70 0.08 -0.46 0.69 -6.44 4.30 0.07 -0.45 0.53 -5.61 3.34 0.03 -0.24 0.26 -0.79 1.61 0.48 _ _ -297.203 28.99 0.12 - - -44.803 7.23 0.11 - - -34.413 6.29 0.07 - - -31.063 3.96 0.04 - - -11.963 2.22 0.01 - -0.49 0.62 v o OJ .Continued Table 25 School District Inpatient Hospital Utilization Equations with DCS, BEOS. BEDSQ and Socioeconomic Variables in 1971. 1981/82 and Pooled 1968-1982/83 Dataset Year & Measure INC SE UNEM SE WHITE SE PRIM SE CONST R2 SE Y Days 1971 MED/SURG 0.07 0.08 -9.99 21.29 -1.95 5.66 -6.61 4.41 1313.09 0.7325 257.79 SURG 0.02 0.02 -5.59 4.45 -1.08 1.18 -0.53 0.92 264.68 0.3537 53.84 SURG-T&A 0.01 0.02 -7.94 4.28 -0.03 1.14 -0.29 0.89 238.25 0.3965 51.80 SURG A 0.01 0.01 0.68 2.24 -0.66 0.60 -0.80 0.46 88.87 0.1698 27.13 SURG B -0.00 0.01 1.39 1.46 -0.861 0.39 -0.29 0.30 64.09 0.0190 17.63 SURG C -0.011 0.00 -0.41 0.50 0.17 0.13 -0.03 0.10 21.60 0.0678 6.09 1981/82 MED/SURG 0.01 0.01 -13.41 7.95 -1.91 2.12 -1.38 1.89 -141.12 0.7719 95.52 SURG 0.01 0.01 2.12 3.06 -0.02 0.82 -0.41 0.73 185.63 0.2966 36.79 SURG-T&A 0.01 0.01 2.57 3.06 0.06 0.82 -0.56 0.73 149.68 0.2514 36.74 SURG A 0.00 0.00 0.73 0.96 0.11 0.26 -0.10 0.23 40.11 0.4324 11.53 SURG B 0.00 0.00 0.58 0.75 -0.21 0.20 0.01 0.18 71.33 0.1513 8.96 SURG C -0.00 0.00 0.811 0.36 -0.12 0.10 -0.08 0.09 20.59 0.1337 4.31 Pooled MED/SURG -0.01 0.01 -29.393 5.74 4.172 1.47 -2.04 1.37 2130.08 0.6721 274.46 1968-83 SURG -0.011 0.00 -3.061 1.43 1.002 0.37 -0.20 0.34 394.08 0.3441 68.48 SURG-T&A -o.oo1 0.00 -3.011 1.25 0.842 0.32 -0.18 0.30 312.16 0.3248 59.51 SURG A -0.003 0.00 -2.402 0.79 0.793 0.20 -0.34 0.19 198.46 0.3832 37.52 SURG B -o.oo3 0.00 0.05 0.44 0.28 0.11 -0.20 0.10 105.06 0.3149 21.05 SURG C -o.oo3 0.00 -0.10 0.12 0.153 0.03 -0.082 0.03 15.48 0.2508 5.87 1 p < 0.05 2 p < 0.01 3 p < 0.001 195 The adjustment f o r the socioeconomic f a c t o r s d i d not b r i n g any r a d i c a l changes t o the a s s o c i a t i o n between bed a v a i l a b i l i t y and i n p a t i e n t u t i l i z a t i o n (Tables 21 and 25). Although r e g r e s s i o n c o e f f i c i e n t on BEDS decreased s l i g h t l y i n MED/SURG equations, the a s s o c i a t i o n remained s t i l l s t r o n g and s t a t i s t i c a l l y h i g h l y s i g n i f i c a n t . The bed e f f e c t on t o t a l s u r g i c a l u t i l i z a t i o n decreased c l e a r l y i n 1981/82 but remained about the same i n 1971 and i n the pooled d a t a s e t . The model t h a t i n c l u d e d socioeconomic v a r i a b l e s , p a e d i a t r i c bed a v a i l a b i l i t y and day care surgery a v a i l a b i l i t y e x p l a i n e d 12-38 perc e n t of the v a r i a t i o n i n o v e r a l l s u r g i c a l admissions and 30-35 per c e n t i n s u r g i c a l p a t i e n t days. Adjustment f o r the e f f e c t s of socioeconomic f a c t o r s had no s i g n i f i c a n t e f f e c t on the a s s o c i a t i o n between day care surgery a v a i l a b i l i t y and i n p a t i e n t u t i l i z a t i o n (Tables 21 and 25). In 1971 the r e g r e s s i o n c o e f f i c i e n t s on DCS remained almost e x a c t l y the same as without adjustment f o r socioeconomic v a r i a b l e s . In 1981/82 the r e g r e s s i o n c o e f f i c i e n t s on DCS i n d i f f e r e n t s u r g i c a l equations remained s t a t i s t i c a l l y i n s i g n i f i c a n t , the o n l y e x c e p t i o n b eing SURG C days f o r which the c o e f f i c i e n t became s t a t i s t i c a l l y s i g n i f i c a n t a t 5 percent l e v e l . R e g r e s s i o n c o e f f i c i e n t s on DCS f o r MED/SURG, SURG and SURG-T&A days i n 1981/82 were p o s i t i v e , although the c o e f f i c i e n t was s t a t i s t i c a l l y s i g n i f i c a n t o n l y f o r MED/SURG equ a t i o n . These p o s i t i v e a s s o c i a t i o n s are hard t o e x p l a i n by the s u b s t i t u t i o n h y p o t h e s i s . In the pooled data the 196 c o e f f i c i e n t on DCS was n e g a t i v e and s t a t i s t i c a l l y s i g n i f i c a n t i n a l l e q u a t i o n s . The r e s u l t s i n 1971 and 1981/82 a f t e r a d j u s t i n g f o r e f f e c t s of soc ioeconomic v a r i a b l e s g i v e more suppor t t o the f i n d i n g t h a t day ca re su r ge ry a v a i l a b i l i t y has no e f f e c t on the o v e r a l l p a e d i a t r i c i n p a t i e n t u t i l i z a t i o n and t h a t e f f e c t on s u r g i c a l u t i l i z a t i o n , i f i t e x i s t s a t a l l , i s f a r from complete s u b s t i t u t i o n . In a d d i t i o n to soc ioeconomic v a r i a b l e s , a v a i l a b i l i t y of d i f f e r e n t p h y s i c i a n s p e c i a l t i e s was a l s o e n t e r e d i n t o the r e g r e s s i o n model f o r the poo led 1973-1982/83 d a t a . The r e g r e s s i o n c o e f f i c i e n t s on DCS i n t h i s poo led d a t a s e t were more s i m i l a r t o those i n i n d i v i d u a l yea r s a f t e r c o n t r o l l i n g f o r bed a v a i l a b i l i t y , soc ioeconomic c h a r a c t e r i s t i c s and p h y s i c i a n a v a i l a b i l i t y ( r e s u l t s a re not p r e s e n t e d i n a t a b l e ) . The c o e f f i c i e n t on DCS was s t a t i s t i c a l l y s i g n i f i c a n t and n e g a t i v e o n l y f o r SURG A, SURG B and SURG C admis s ions and SURG B and SURG C days , i m p l y i n g s u b s t i t u t i o n o f l e s s than 12 p e r c e n t (SURG B - t y p e ) . The c o e f f i c i e n t on bed a v a i l a b i l i t y remained e s s e n t i a l l y the same and was s t a t i s t i c a l l y h i g h l y s i g n i f i c a n t f o r a l l e q u a t i o n s . The a d j u s t e d R 2 f o r MED/SURG admis s ions and days equat ions was c l e a r l y improved (71 pe rcen t and 77 p e r c e n t , r e s p e c t i v e l y ) . A f t e r e x p l o r i n g the p o s s i b l e con found ing e f f e c t of s e v e r a l s o c i a l , demographic and economic f a c t o r s and p h y s i c i a n a v a i l a b i l i t y , the c a u s a l e f f e c t from beds t o u t i l i z a t i o n seems even more p l a u s i b l e . 197 4.6.3 Unmeasured confound ing f a c t o r s I t i s p o s s i b l e t h a t t h e r e a re s t i l l o t h e r con found ing i n f l u e n c e s t h a t the s tudy v a r i a b l e s have not been a b l e t o c o n t r o l . A l s o , the e x p l a i n e d v a r i a t i o n i n the poo led c r o s s -a r e a / c r o s s - y e a r da ta has been l e s s than 80 p e r c e n t f o r o v e r a l l p a e d i a t r i c i n p a t i e n t u t i l i z a t i o n i m p l y i n g , t h a t t h e r e a re f a c t o r s t h a t have not been i d e n t i f i e d . The c r o s s - a r e a / c r o s s -y e a r d e s i g n a l l ows some c o n t r o l f o r unmeasured con found ing f a c t o r s t h a t a r e s p e c i f i c t o i n d i v i d u a l yea r s but common a c r o s s d i s t r i c t s ( genera l tempora l e f f e c t s ) , o r t h a t a re s p e c i f i c f o r a d i s t r i c t but cons tan t over t ime ( d i s t r i c t -s p e c i f i c e f f e c t s ) . In o r d e r t o a d j u s t the r e l a t i o n s h i p between day ca re su r ge ry a v a i l a b i l i t y , bed a v a i l a b i l i t y and p a e d i a t r i c i n p a t i e n t u t i l i z a t i o n f o r unmeasured t i m e - and d i s t r i c t - s p e c i f i c f a c t o r s , s e v e r a l dummy v a r i a b l e s were c r e a t e d . Fo r y e a r -s p e c i f i c confounders a s e t of t e n t ime dummies was c o n s t r u c t e d , each of which had a v a l u e of 1.0 i n one s p e c i f i c y e a r and zero i n a l l o t h e r s . One o f the e l e v e n yea r s (1982/83) was l e f t w i thou t a dummy v a r i a b l e to p reven t c o l l i n e a r i t y w i t h the cons tan t term. S i m i l a r l y a s e t of 74 s c h o o l d i s t r i c t - s p e c i f i c dummy v a r i a b l e s was c r e a t e d , each of which had a v a l u e of 1.0 i n o b s e r v a t i o n s on i t s own s c h o o l d i s t r i c t , and zero f o r a l l o t h e r s . One s c h o o l d i s t r i c t 198 (Vancouver, no. 39) was l e f t w i thout a d i s t r i c t dummy f o r the above ment ioned r e a s o n . T a b l e 26 r e p o r t s r e s u l t s w i thout adjustment f o r t i m e - and d i s t r i c t - s p e c i f i c confounders and a f t e r a d j u s t i n g f o r t i m e -s p e c i f i c confounders , s c h o o l d i s t r i c t - s p e c i f i c confounders and t i m e - and d i s t r i c t - s p e c i f i c con founder s . Because the number o f v a r i a b l e s i n the equa t i on w i t h d i s t r i c t dummies and d i s t r i c t and y e a r dummies i s h i gh u s i n g up a g r e a t many s t a t i s t i c a l degrees of f reedom, the ana l y se s were done o n l y w i t h the l a r g e poo led 1968-1982/83 c r o s s - a r e a / c r o s s - y e a r d a t a . C o e f f i c i e n t s f o r the dummy v a r i a b l e s a r e not r e p o r t e d i n the t a b l e s i n c e the se were i n t r o d u c e d o n l y t o c o n t r o l f o r con found ing e f f e c t i n the r e l a t i o n s h i p between main s tudy v a r i a b l e s . However, t h e r e were s i g n i f i c a n t t i m e - and d i s t r i c t -s p e c i f i c e f f e c t s which a r e d i s c u s s e d b r i e f l y below. When both t ime and d i s t r i c t dummies were e n t e r e d i n t o the equa t i on s w i t h the DCS and BEDS v a r i a b l e s , a l l the d i f f e r e n t t ime dummies showed s t a t i s t i c a l l y h i g h l y s i g n i f i c a n t p o s i t i v e c o e f f i c i e n t f o r a l l admis s ion and h o s p i t a l day e q u a t i o n s , the o n l y e x c e p t i o n be ing the 1981/82 dummy. The y e a r 1981/82 showed s t a t i s t i c a l l y s i g n i f i c a n t a s s o c i a t i o n (at the f i v e p e r c e n t l e v e l ) o n l y w i t h SURG, SURG A and SURG B admis s ions and SURG B days . In g e n e r a l , the v a l u e of the t ime dummy c o e f f i c i e n t dec rea sed s t e a d i l y from 1968 t o 1981/82, r e f l e c t i n g a g e n e r a l tempora l e f f e c t o f r e d u c i n g p a e d i a t r i c Table 26 School District Inpatient Hospital Utilization Equations with DCS. BEDS, BEDSQ and Time and/or District Dunniies in Pooled 1968-82/83 Dataset Admissions Measure DCS SE BEDS SE BEDSQ SE CONST R2 SE Y MED/SURG -0.673 0.17 37.823 2.68 -1.283 0.26 36.30 0.5744 40.15 Time Dummy 0.431 0.19 37.673 2.54 -1.223 0.24 -3.14 0.6265 37.61 District Ouimiy -1.523 0.16 20.703 3.24 -1.023 0.27 66.93 0.7951 27.86 Time & Oist Dummy 0.663 0.18 11.433 2.85 -0.501 0.23 11.32 0.8608 22.97 SURG -0.583 0.05 4.673 0.84 -0.353 0.08 40.75 0.1946 12.55 Time Dummy -0.04 0.05 4.563 o:69 -0.313 0.07 19.93 0.4583 10.29 District Duimry -0.993 0.06 4.323 1.23 -0.261 0.10 48.49 0.4256 , 10.60 Time & Dist Duimry -0.09 0.07 2.892 1.06 -0.171 0.09 24.39 0.6278 8.53 SURG-T&A -0.173 0.03 3.273 0.44 -0.183 0.04 22.60 0.2088 6.62 Time Dunny 0.01 0.03 3.233 0.42 -0.173 0.04 15.51 0.3049 6.21 District Dumny -0.313 0.03 3.953 0.66 -0.213 0.06 25.75 0.4143 5.70 Time & Dist Duimry -0.04 0.04 3.633 0.67 -0.193 0.06 18.30 0.4774 5.38 SURG A -0.623 0.05 3.013 0.75 -0.222 0.07 30.26 0.2137 11.23 Time Dummy -0.08 0.04 2.743 0.59 -0.182 0.06 9.37 0.5286 8.70 District Duimry -1.023 0.05 2.751 1.09 -0.14 0.09 37.82 0.4521 9.38 Time & Dist Dunny -0.10 0.06 0.47 0.86 0.00 0.07 14.12 0.6997 6.94 SURG B -0.523 0.04 2.132 0.68 -0.192 0.07 27.69 0.1704 10.20 Time Dunny -0.07 0.04 1.893 0.56 -0.152 0.05 10.29 0.4471 8.33 District Duimry -0.853 0.05 1.79 0.97 -0.09 0.08 33.95 0.4391 8.39 Time & Dist Duimry -0.10 0.05 -0.15 0.82 0.03 0.07 14.52 0.6549 6.58 SURG C -0.063 0.01 0.803 0.19 -0.062 0.02 6.00 0.0645 2.81 Time Dummy -0.01 0.01 0.603 0.18 -0.041 0.02 3.61 0.1698 2.65 District Durrmy -0.113 0.01 1.453 0.26 -0.072 0.02 6.40 0.3984 2.25 Time & Dist Dummy -0.073 0.02 0.601 0.26 -0.02 0.02 5.57 0.4650 2.12 1 p < 0.05 2 p < 0.01 3 p < 0.001 ntinued Table 26 School District Inpatient Hospital Utilization Equations with DCS, BEDS, BEDSQ and Time and/or District Dunmies in Pooled 1968-82/83 Dataset Days Measure DCS SE BEDS SE BEDSQ SE CONST R2 SE Y MED/SURG -7.953 1.33 248.133 20.55 -5.312 1.97 146.73 0.5888 307.37 Time Dummy 4.322 1.35 247.533 17.76 -4.682 1.69 -276.38 0.6985 263.17 District Duiimy -16.323 1.38 152.963 28.39 -5.321 2.40 434.97 0.7400 244.39 Time & Dist Dummy 7.323 1.46 83.453 22.65 -1.29 1.85 -154.06 0.8546 182.79 SURG -2.993 0.31 37.593 4.77 -2.033 0.46 162.16 0.2892 71.29 Time Dummy 0.45 0.29 37.773 3.77 -1.863 0.36 42.10 0.5633 55.88 District Duirniy -5.233 0.37 46.883 7.55 -2.853 0.64 199.89 0.4088 65.02 Time & Dist Dunmy 0.66 0.41 42.073 6.38 -2.503 0.52 49.67 0.6297 51.46 SURG-T&A -1.863 0.27 32.873 4.11 -1.583 0.39 123.36 0.2785 61.52 Time Dunmy 0.732 0.27 32.963 3.51 -1.453 0.33 34.04 0.4935 51.96 District Dumny -3.553 0.32 45.603 6.51 -2.663 0.55 149.14 0.4012 56.04 Time & Dist Dummy 0.791 0.38 42.643 5.94 -2.443 0.49 39.72 0.5617 47.95 SURG A -2.243 0.18 15.433 2.71 -0.833 0.26 78.84 0.2806 40.52 Time Dunmy -0.18 0.16 14.683 2.06 -0.673 0.20 2.65 0.5904 30.57 District Dummy -3.633 0.21 16.453 4.22 -1.052 0.36 106.53 0.4212 36.35 Time & Dist Dunmy -0.04 0.22 8.321 3.36 -0.551 0.28 15.05 0.6776 27.13 SURG B -1.303 0.10 4.942 1.51 -0.392 0.14 60.31 0.2111 22.58 Time Dunmy -0.272 0.09 4.343 1.23 -0.301 0.12 20.54 0.4898 18.16 District Dumny -2.003 0.11 4.17 2.19 -0.18 0.19 75.11 0.4516 18.83 Time & Dist Dummy -0.231 0.12 -0.58 1.78 0.11 0.15 29.26 0.6813 14.35 SURG C -0.173 0.03 1.523 0.43 -0.091 0.04 14.27 0.0951 6.45 Time Dunmy -0.02 0.03 1.072 0.40 -0.05 0.04 7.15 0.2269 5.96 District Dumny -0.333 0.03 2.913 0.62 -0.111 0.05 16.34 0.3859 5.32 Time & Dist Dummy -0.143 0.04 0.97 0.62 0.00 0.05 12.01 0.4617 4.98 1 p < 0.05 2 p < 0.01 3 p < 0.001 201 h o s p i t a l i z a t i o n s d u r i n g the study p e r i o d independent of day care s u r g e r y use and p a e d i a t r i c bed c a p a c i t y . Over h a l f of the d i f f e r e n t s c h o o l d i s t r i c t s showed p o s i t i v e and s t a t i s t i c a l l y s i g n i f i c a n t r e g r e s s i o n c o e f f i c i e n t f o r MED/SURG admissions and around 40 percent f o r MED/SURG days. None showed s t a t i s t i c a l l y s i g n i f i c a n t n e g a t i v e c o e f f i c i e n t s . T h i s i m p l i e s t h a t s e v e r a l s c h o o l d i s t r i c t s i n B.C. have had h i g h e r p a e d i a t r i c h o s p i t a l i z a t i o n p a t t e r n s than Vancouver, and no one has had s i g n i f i c a n t l y lower h o s p i t a l i z a t i o n p r a c t i c e f o r a g i v e n bed stock and day care surgery use. A subsequent a n a l y s i s showed t h a t t h i s d i f f e r e n c e i n h o s p i t a l i z a t i o n p a t t e r n s between Vancouver and o t h e r s c h o o l d i s t r i c t s was a l s o independent from socioeconomic c h a r a c t e r i s t i c s . Of the d i f f e r e n t s c h o o l d i s t r i c t s , L i l l o o e t (no. 29) and F o r t Nelson (no. 81) showed the h i g h e s t d i s t r i c t - s p e c i f i c p a e d i a t r i c h o s p i t a l i z a t i o n p a t t e r n s . D i s t r i c t - s p e c i f i c dummy v a r i a b l e s showed t h a t n e a r l y 20 per c e n t of s c h o o l d i s t r i c t s have had s i g n i f i c a n t l y h i g h e r and about 15 perc e n t have had s i g n i f i c a n t l y lower s u r g i c a l admission r a t e s f o r the p a e d i a t r i c age group than Vancouver. However, o n l y one s c h o o l d i s t r i c t (Vancouver I s l a n d West, no. 84) has had h i g h e r s u r g i c a l day r a t e than Vancouver (independent from DCS, BEDS and t i m e - s p e c i f i c e f f e c t s ) . A g a s s i z (no. 76) and Summerland (no. 77) showed the lowest p a e d i a t r i c s u rgery u t i l i z a t i o n (admissions and h o s p i t a l d a y s ) . 202 Almost a l l s c h o o l d i s t r i c t s showed lower SURG-T&A u t i l i z a t i o n f o r a g i v e n bed stock and day care surgery use than Vancouver. Golden (no. 18) and A g a s s i z (no. 76) showed the lowest r e g r e s s i o n c o e f f i c i e n t s f o r SURG-T&A admissions and days. A s l i g h t l y more s c h o o l d i s t r i c t s had a s i g n i f i c a n t p o s i t i v e c o e f f i c i e n t on d i s t r i c t dummy than a s i g n i f i c a n t n e g a t i v e one f o r SURG A and SURG B equations. The m a j o r i t y of s c h o o l d i s t r i c t s had i n s i g n i f i c a n t c o e f f i c i e n t f o r these measures. N e a r l y one t h i r d of the s c h o o l d i s t r i c t s showed s i g n i f i c a n t n e g a t i v e r e g r e s s i o n c o e f f i c i e n t f o r SURG C u t i l i z a t i o n , whereas o n l y few d i s t r i c t s showed s i g n i f i c a n t p o s i t i v e c o e f f i c i e n t s , i m p l y i n g t h a t most of the s c h o o l d i s t r i c t s i n B.C. have had SURG C u t i l i z a t i o n r a t e s equal t o or lower than t h a t i n Vancouver g i v e n constant bed c a p a c i t y and day care s u r g e r y use. Golden (no. 18) showed the lowest SURG C u t i l i z a t i o n p a t t e r n s . Adjustment f o r the f a c t o r s t h a t are s p e c i f i c t o a year but constant a c r o s s d i s t r i c t s , such as changes i n s u r g i c a l p r a c t i c e p a t t e r n s over time, i m p l i e d t h a t day care s u r g e r y a v a i l a b i l i t y does not have any s u b s t i t u t i o n e f f e c t on the o v e r a l l m e d i c a l / s u r g i c a l i n p a t i e n t u t i l i z a t i o n (Table 26). The r e g r e s s i o n c o e f f i c i e n t on DCS was p o s i t i v e and s t a t i s t i c a l l y s i g n i f i c a n t f o r both MED/SURG admissions and p a t i e n t days, i m p l y i n g t h a t day care surgery a v a i l a b i l i t y w i l l i n c r e a s e o v e r a l l i n p a t i e n t u t i l i z a t i o n w i t h a g i v e n bed stock when time-dependent confounding f a c t o r s are c o n t r o l l e d . The 203 goodness of f i t f o r the o v e r a l l e q u a t i o n i s c l e a r l y improved (from 57 p e r c e n t t o 63 pe rcen t f o r admiss ions and from 59 p e r c e n t t o 7 0 p e r c e n t f o r d a y s ) , w i t h the a d d i t i o n of the t ime dummies. T h i s i m p l i e s the e x i s t e n c e o f f a c t o r s not c ap tu red i n the i n c l u d e d e x p l a n a t o r y v a r i a b l e s (DCS, BEDS, BEDS 2 ) , t h a t had the independent e f f e c t of r e d u c i n g u t i l i z a t i o n over t ime . Adjustment f o r t ime f a c t o r s i n f l u e n c e d a l s o the a s s o c i a t i o n between day c a r e su r ge ry and s u r g i c a l i n p a t i e n t u t i l i z a t i o n . The c o e f f i c i e n t on DCS f e l l marked ly and became s t a t i s t i c a l l y i n s i g n i f i c a n t (and p o s i t i v e i n the h o s p i t a l day equa t i on ) f o r o v e r a l l s u r g i c a l u t i l i z a t i o n . The p a t t e r n was e x a c t l y the same f o r s u r g i c a l u t i l i z a t i o n e x c l u d i n g T&As, and the p o s i t i v e c o e f f i c i e n t on DCS f o r h o s p i t a l days was s t a t i s t i c a l l y s i g n i f i c a n t . The e x p l a i n e d v a r i a n c e i n t o t a l s u r g i c a l u t i l i z a t i o n i n c r e a s e d s u b s t a n t i a l l y (from 20 t o 46 p e r c e n t f o r admi s s ions and from 29 t o 56 p e r c e n t f o r h o s p i t a l d a y s ) . The improvement o f f i t i n the o v e r a l l r e g r e s s i o n e q u a t i o n f o r SURG-T&A was s l i g h t l y l e s s , but s t i l l s u b s t a n t i a l . The r e g r e s s i o n c o e f f i c i e n t s on DCS became i n s i g n i f i c a n t a l s o i n the SURG A, B and C equa t i ons (except f o r the days equa t i on f o r SURG B) a f t e r adjustment f o r t i m e - s p e c i f i c con found ing f a c t o r s . The adjustment f o r t i m e - s p e c i f i c confounders improved the a d j u s t e d c o e f f i c i e n t o f d e t e r m i n a t i o n s u b s t a n t i a l l y a l s o i n these more r e s t r i c t e d s u r g i c a l c a t e g o r i e s . 2 0 4 The above d e s c r i b e d f i n d i n g s c o n f i r m more o r l e s s what was a l r e a d y found when s t u d y i n g i n d i v i d u a l year s s e p a r a t e l y . Day ca re s u r g e r y a v a i l a b i l i t y may have weak s u b s t i t u t i o n e f f e c t i n more na r row ly d e f i n e d , day c a r e e l i g i b l e i n p a t i e n t su r ge ry c a t e g o r i e s , but t h i s s u b s t i t u t i o n e f f e c t d i s a p p e a r s a t the l e v e l of t o t a l s u r g e r y , even b e f o r e r e a c h i n g the m e d i c a l s i d e . The r e g r e s s i o n c o e f f i c i e n t s imp ly t h a t the s u b s t i t u t i o n f o r s u r g i c a l i n p a t i e n t u t i l i z a t i o n i s o n l y few p e r c e n t and w e l l over 9 0 p e r c e n t of day ca re su r ge ry use r e p r e s e n t s g e n e r a t i o n o f new s u r g e r y . The adjustment f o r p o t e n t i a l confound ing t i m e - s p e c i f i c f a c t o r s d i d not a f f e c t s i g n i f i c a n t l y the bed a v a i l a b i l i t y e f f e c t on p a e d i a t r i c i n p a t i e n t u t i l i z a t i o n , f u r t h e r s t r e n g t h e n i n g the p l a u s i b i l i t y of a c a u s a l e f f e c t from beds to u t i l i z a t i o n . Reg re s s i on c o e f f i c i e n t s on BEDS and BEDS 2 remained a lmost e x a c t l y the same i n a l l MED/SURG, SURG and SURG-T&A equa t i on s (Tab le 26) . The impact o f beds on day ca re e l i g i b l e s u r g i c a l u t i l i z a t i o n dec reased o n l y s l i g h t l y a f t e r adjustment f o r t i m e - s p e c i f i c dummies. S choo l d i s t r i c t dummies improved s i g n i f i c a n t l y the goodness o f f i t o f MED/SURG equa t i on s ( from 5 7 t o 8 0 p e r c e n t f o r days and from 5 9 t o 7 4 p e r c e n t f o r days) (Tab le 2 6 ) . The a d d i t i o n a l v a r i a t i o n e x p l a i n e d was g r e a t e r than w i t h t ime dummies a l o n e , i m p l y i n g g r e a t e r importance of d i s t r i c t s p e c i f i c f a c t o r s i n d e t e r m i n i n g v a r i a t i o n i n p a e d i a t r i c i n p a t i e n t u t i l i z a t i o n 205 r a t e s . A l s o , these d i s t r i c t s p e c i f i c f a c t o r s seemed t o have more impact on admi s s ion r a t e s than on l e n g t h of s t a y . The i n c l u s i o n of d i s t r i c t dummies i n the r e g r e s s i o n equa t i on s does not c o n t r o l f o r the c o i n c i d i n g t r ends o f d e c r e a s i n g T&A r a t e and i n c r e a s i n g day ca re su r ge ry u t i l i z a t i o n over t ime (which a re suggested t o be independent by the r e s u l t s from i n d i v i d u a l y e a r s ) , and thus the r e g r e s s i o n c o e f f i c i e n t on DCS i s n e g a t i v e and h i g h l y s i g n i f i c a n t . As e x p e c t e d , the a s s o c i a t i o n between DCS and i n p a t i e n t u t i l i z a t i o n i s lowest i n those equa t i on s t h a t e x c l u d e T&As (SURG-T&A and SURG C ) . The r e g r e s s i o n c o e f f i c i e n t s imp ly t h a t 100 day ca re su r ge ry cases would have saved 152 i n p a t i e n t admiss ions w i t h average l e n g t h of s t a y of 10.7 days . N i n e t y n ine of these admiss ions would have been f o r s u r g e r y w i t h average l e n g t h of s t a y of 5.3 days . The p l a u s i b i l i t y t h a t t h i s r e f l e c t s a c a u s a l e f f e c t from DCS t o i n p a t i e n t u t i l i z a t i o n has a l r e a d y been q u e s t i o n e d by p r e v i o u s r e s u l t s . I n t r o d u c t i o n of d i s t r i c t s p e c i f i c dummies dec reased s l i g h t l y the r e g r e s s i o n c o e f f i c i e n t s on bed a v a i l a b i l i t y f o r the MED/SURG e q u a t i o n s , but the c o e f f i c i e n t s s t i l l remained s t a t i s t i c a l l y h i g h l y s i g n i f i c a n t . D i s t r i c t d i f f e r e n c e s i n bed a v a i l a b i l i t y would be one of the p r i n c i p a l sources o f d i s t r i c t s p e c i f i c , t i m e - i n v a r i a n t e f f e c t s , l e a d i n g t o a h i g h c o r r e l a t i o n between BEDS and the d i s t r i c t s p e c i f i c dummies. However, the improvement of f i t of the equa t i on s suggests t h a t t h e r e a re a l s o o t h e r impor tant d i s t r i c t s p e c i f i c e f f e c t s . The 206 bed a v a i l a b i l i t y e f f e c t remained about the same or increased s l i g h t l y f o r the d i f f e r e n t surgical equations a f t e r adjusting for d i s t r i c t - s p e c i f i c e f f e c t s , exception being SURG B equation i n which the c o e f f i c i e n t on BEDS decreased and became s t a t i s t i c a l l y i n s i g n i f i c a n t both for admissions and days. The adjustment for both time and d i s t r i c t dummies yielded the highest adjusted c o e f f i c i e n t s of determination (86 percent for MED/SURG admissions, 63 percent for SURG admissions, 86 percent for MED/SURG days, and 63 percent for SURG days) (Table 26). The association between DCS and medical/surgical u t i l i z a t i o n became again p o s i t i v e and s t a t i s t i c a l l y s i g n i f i c a n t . The association with o v e r a l l s u r g i c a l admissions was negative but i n s i g n i f i c a n t and the association with s u r g i c a l days was pos i t i v e and also i n s i g n i f i c a n t . The si t u a t i o n was the same with SURG-T&A, but the p o s i t i v e c o e f f i c i e n t for hospital days was s t a t i s t i c a l l y s i g n i f i c a n t . Only SURG C equations showed a consistent s i g n i f i c a n t negative impact of DCS for both admissions and hospital days. However, the size of t h i s impact was small implying less than 10 percent substitution by DCS i n t h i s subcategory of su r g i c a l u t i l i z a t i o n . Simultaneous adjustment for time and school d i s t r i c t dummies decreased the bed e f f e c t on o v e r a l l paediatric h o s p i t a l u t i l i z a t i o n , but the association remained s t i l l powerful and s t a t i s t i c a l l y s i g n i f i c a n t for both admissions and days (Table 207 26) . The observed bed a v a i l a b i l i t y e f f e c t i s c l e a r l y not r e f l e c t i n g a spu r i ou s a s s o c i a t i o n t h a t c o u l d be e x p l a i n e d by some o t h e r v a r i a b l e . The s imul taneous adjustment dec rea sed the impact o f beds on s u r g i c a l admis s ions but not on h o s p i t a l days . But here as w e l l the c o e f f i c i e n t on BEDS remained l a r g e and s t a t i s t i c a l l y s i g n i f i c a n t . The adjustment p rocedure d i d not have any e f f e c t on the r e l a t i o n s h i p between bed a v a i l a b i l i t y and SURG-T&A u t i l i z a t i o n . The e f f e c t on a l l day c a r e s u r g e r y - e l i g i b l e u t i l i z a t i o n measures f e l l and became s t a t i s t i c a l l y i n s i g n i f i c a n t f o r SURG A and B admis s ions and SURG B and C days . The s c h o o l d i s t r i c t i n p a t i e n t h o s p i t a l u t i l i z a t i o n equa t i ons were c a l c u l a t e d a l s o i n c l u d i n g DCS, BEDS, BEDS 2 , the d i f f e r e n t soc ioeconomic v a r i a b l e s , and t i m e - and d i s t r i c t - s p e c i f i c dummies s i m u l t a n e o u s l y i n t o the model i n the poo led 1968-1982/83 d a t a s e t (Tab le 27) . The a d d i t i o n a l adjustment f o r the soc ioeconomic v a r i a b l e s improved s l i g h t l y the a d j u s t e d c o e f f i c i e n t o f d e t e r m i n a t i o n f o r the MED/SURG days e q u a t i o n . The r e g r e s s i o n c o e f f i c i e n t on DCS was p o s i t i v e and s t a t i s t i c a l l y s i g n i f i c a n t f o r MED/SURG admis s ions and days , i m p l y i n g t h a t 100 day ca re su r ge ry cases would i n c r e a s e o v e r a l l p a e d i a t r i c i n p a t i e n t admiss ions by 58 w i t h the average l e n g t h o f s t a y of 8.7 days . The o n l y s i g n i f i c a n t n e g a t i v e c o e f f i c i e n t s on DCS were found f o r SURG C admis s ions and days , i m p l y i n g t h a t 100 day c a r e su r ge ry cases would s u b s t i t u t e f o r 10 p a e d i a t r i c i n p a t i e n t admiss ions of SURG C - t y p e , w i t h the . C o n t i n u e d Table 27 School District Inpatient Hospital Utilization Equations with DCS. BEDS. BEDSQ, Socioeconomic Variables and Time and District Dutnnies in Pooled 1968-1982/83 Dataset 2 0 8 Measure DCS SE BEDS SE BEDSQ SE CONST R2 SE Y Admissions: MED/SURG 0.582 0.19 11.933 2.85 -0.531 0.23 170.26 0.8641 22.69 SURG -0.03 0.07 2.832 1.05 -0.13 0.09 -18.82 0.6452 8.33 SURG-T&A 0.01 0.04 3.743 0.65 -0.172 0.05 -9.28 0.5153 5.18 SURG A 0.07 0.06 0.30 0.86 0.03 0.07 -21.08 0.7081 6.84 SURG B -0.06 0.05 -0.36 0.81 0.07 0.05 -34.00 0.6668 6.46 SURG C -0.052 0.02 0.561 0.26 -0.01 0.02 -15.68 0.4972 2.03 Days: MED/SURG 5.073 1.43 97.053 21.82 -2.74 1.78 3005.56 0.8685 173.80 SURG 0.59 0.42 44.403 6.41 -2.573 0.52 388.31 0.6354 51.06 SURG-T&A 0.75 0.39 45.183 5.97 -2.533 0.49 387.55 0.5685 47.57 SURG A -0.12 0.22 8.511 3.40 -0.54 0.28 125.39 0.6786 27.08 SURG B -0.18 0.12 -1.01 1.78 0.18 0.15 -40.91 0.6895 14.17 SURG C -0.102 0.04 0.87 0.61 0.03 0.05 -24.91 0.4889 4.85 1 p < 0.05 2 p < 0.01 3 p < 0.001 2 0 9 average l e n g t h of s t a y of 2 days. The r e g r e s s i o n c o e f f i c i e n t s on B E D S were e s s e n t i a l l y the same as without the adjustment f o r the socioeconomic v a r i a b l e s , s u g g e s t i n g a non-spurious a s s o c i a t i o n between p a e d i a t r i c bed a v a i l a b i l i t y and p a e d i a t r i c i n p a t i e n t h o s p i t a l u t i l i z a t i o n . 4 . 7 . Roemer's Law and d e c r e a s i n g bed su p p l y In o r d e r t o examine the c o n s i s t e n c y of bed a v a i l a b i l i t y e f f e c t i n p o l i c y environments of i n c r e a s i n g o r s t a b l e bed c a p a c i t y on the one hand, and d e c r e a s i n g bed supply on the ot h e r , s p e c i a l time dummy v a r i a b l e s , REnsn and B E J Q S C J D , were c r e a t e d . The B E D S D v a r i a b l e had the va l u e of zero i n 1 9 6 8 - 1 9 7 4 when the bed c a p a c i t y i n the Provinc e was s l i g h t l y i n c r e a s i n g , and the v a l u e of the B E D S v a r i a b l e i n 1 9 7 5 - 1 9 7 6 and 1 9 8 1 / 8 2 -1 9 8 2 / 8 3 when bed c a p a c i t y was g e n e r a l l y d e c r e a s i n g . The B E D S Q D v a r i a b l e had the v a l u e of zero i n 1 9 6 8 - 1 9 7 4 and the v a l u e of the B E D S 2 v a r i a b l e i n 1 9 7 5 - 1 9 7 6 and 1 9 8 1 / 8 2 - 8 2 / 8 3 . I n c l u s i o n of these v a r i a b l e s i n t o the r e g r e s s i o n e quation can be d e s c r i b e d as f o l l o w s : Y = a + b(DCS) + c(BEDS) + d(BEDS 2) + e(BEDSD) + f(BEDSQD) 210 w h e r e a i s t h e i n t e r c e p t , b i s t h e r e g r e s s i o n c o e f f i c i e n t o n D C S , c i s t h e c o e f f i c i e n t o n B E D S , a n d d i s t h e c o e f f i c i e n t o n B E D S 2 . S y m b o l e i s t h e r e g r e s s i o n c o e f f i c i e n t o n BEDSD a n d f i s t h e c o e f f i c i e n t o n B E D S Q D . I n 1968-1974 BEDSD = 0 a n d BEDSQD = 0, b u t i n 1974-1976 a n d 1981/82-82/83 BEDSD = BEDS a n d BEDSQD = B E D S 2 . I f t h e b e d a v a i l a b i l i t y e f f e c t i s h i g h e r d u r i n g t h e y e a r s w h e n b e d c a p a c i t y i s d e c r e a s i n g (1975-1982/83), t h e n t h e r e g r e s s i o n e q u a t i o n w i t h BEDSD a n d BEDSQD v a r i a b l e s w o u l d s h o w a p o s i t i v e a n d s i g n i f i c a n t c o e f f i c i e n t o n BEDSD i n t h e p o o l e d 1968-1982/83 d a t a s e t . A n e g a t i v e a n d s t a t i s t i c a l l y s i g n i f i c a n t c o e f f i c i e n t o n BEDSD w o u l d i m p l y a l o w e r b e d a v a i l a b i l i t y e f f e c t i n a n e n v i r o n m e n t o f d e c r e a s i n g b e d c a p a c i t y . T a b l e 28 s h o w s t h a t e , o r t h e r e g r e s s i o n c o e f f i c i e n t o n BEDSD was n e g a t i v e , a n d s t a t i s t i c a l l y s i g n i f i c a n t , a n d f , o r t h e r e g r e s s i o n c o e f f i c i e n t o n BEDSQD was p o s i t i v e a n d a l s o s t a t i s t i c a l l y s i g n i f i c a n t i n a l l e q u a t i o n s o f i n p a t i e n t u t i l i z a t i o n . T h e a d j u s t m e n t f o r BEDSD a n d BEDSQD i m p r o v e d s u b s t a n t i a l l y t h e g o o d n e s s o f t h e f i t o f t h e o v e r a l l e q u a t i o n s ( T a b l e s 21 a n d 28). T h e r e g r e s s i o n e q u a t i o n f o r t h e Table 28 School D i s t r i c t Inpa t i en t Hosp i t a l U t i l i z a t i o n Equat ions w i t h DCS. BEDS. BEDSQ. BEDSD and BEDSQD in Pooled 1968-82/83 Dataset Measure DCS SE BEDS SE BEDSQ SE BEDSD SE BEDSQD SE CONST R 2 SE Y Admiss ions: MED/SURG -0 .11 0.17 42 .14 3 2.58 - 1 . 5 4 3 0.25 - 1 1 . 0 5 3 1.77 0 . 6 6 1 0.29 28 .33 0.6184 38.02 SURG - 0 . 3 5 3 0.05 6 . 50 3 0.78 - 0 . 5 3 3 0.08 - 6 . 1 2 3 0.53 0 . 6 6 3 0.09 38 .34 0.3321 11.43 SURG-T&A - 0 . 0 9 2 0.03 3 .84 3 0.44 - 0 . 2 4 3 0.04 - 1 . 8 8 3 0.30 0 . 2 0 3 0.05 21.83 0.2547 6.43 SURG A - 0 . 3 9 3 0.05 4 . 83 3 0.68 - 0 . 3 9 3 0.07 - 5 . 8 5 3 0.46 0 . 5 9 3 0 .08 27.69 0.3803 9.97 SURG B - 0 . 3 3 3 0.04 3 .66 3 0.63 - 0 . 3 4 3 0.06 - 5 . 0 1 3 0.43 0 . 5 3 3 0.07 25.63 0.3188 9.24 SURG C - 0 . 0 3 2 0.01 0 . 98 3 0.19 - 0 . 0 8 3 0.02 - 0 . 6 7 3 0.13 0 . 0 8 3 0.02 5.82 0.0943 2.76 Days: MED/SURG -1 .96 1.24 294 .63 3 18.43 - 7 . 6 5 3 1.79 -109 .46 3 12.63 4 . 6 4 1 2.04 54 .73 0.6799 271.16 SURG - 1 . 5 7 3 0.29 4S .72 3 4.31 - 2 . 8 0 3 0.42 - 30 . 48 3 2.95 2 . 2 3 3 0.48 142.97 0.4378 63.40 SURG-T&A - 0 . 7 9 2 0.26 41 .19 3 3.83 - 2 . 1 0 3 0.37 - 21 . 57 3 2.62 1 .35 2 0.42 108.22 0.3958 56.30 SURG A - 1 . 3 7 3 0.16 22 .29 3 2.41 - 1 . 3 9 3 0.23 - 20 . 34 3 1.65 1.-783 0.27 68 .04 0.4502 35.42 SURG B - 0 . 8 6 3 0.09 8 . 4 1 3 1.38 - 0 . 7 2 3 0.13 - 1 1 . 20 3 0.95 1 .14 3 0.15 55.44 0.3611 20.32 SURG C - 0 . 1 0 3 0.03 2 .09 3 0.43 - 0 . 1 5 3 0.04 - 1 . 9 9 3 0.29 0 . 2 3 3 0.05 13.60 0.1499 6.26 1 p < 0.05 2 p < 0.01 3 p < 0.001 212 m e d i c a l / s u r g i c a l admiss ions can be now w r i t t e n i n 1968-1974 a s : MED/SURG(a) = 28.33 - O. l l (DCS) + 42.14(BEDS) - ' 1 . 5 4 ( B E D S 3 ) and f o r h o s p i t a l days MED/SURG(d) = 54.73 - 1.96(DCS) + 294.63(BEDS) - 7 . 6 5 ( B E D S 2 ) . In y e a r s 1975-1982/83 the same equa t ions a re M/S(a) = 28.33 - O. l l (DCS) + 31.09(BEDS) - 0.88(BEDS 2 ) M/S(d) = 54.73 - 1.96(DCS) + 185.17(BEDS) - 3.01(BEDS 2 ) The c o r r e s p o n d i n g equat ions w i thout BEDSD and BEDSQD adjustment from the Tab le 21 a r e : M/S(a) = 36.30 - 0.67(DCS) + 37.82(BEDS) - 1.28(BEDS 2 ) M/S(d) = 146.73 - 7.95(DCS) + 248.13(BEDS) - 5 .31(BEDS 2 ) . These equa t i on s imp ly t h a t one a d d i t i o n a l bed a t the e x i s t i n g bed supp l y of 3/1,000 would have c r e a t e d 32.9 a d d i t i o n a l admis s ions pe r yea r i n 1968-1974 w i t h marg i na l average l e n g t h of s t a y of 7.6 days , 25.8 a d d i t i o n a l admi s s ions pe r y e a r i n 1975-1982/83 w i t h marg i na l l e n g t h of s t a y of 6.5 days , and g i v e n the equa t i ons i n T a b l e 21 f o r t h e 213 whole p e r i o d o f 1968-1982/83, 30.1 a d d i t i o n a l admis s ions w i t h average l e n g t h of s t a y of 7.2 days . These r e s u l t s suggests t h a t i n the p o l i c y environment of d e c r e a s i n g a v a i l a b i l i t y of p a e d i a t r i c beds the e f f e c t of bed supp l y on p a e d i a t r i c i n p a t i e n t u t i l i z a t i o n i s l e s s than when the bed supp l y i s s t a b l e o r i n c r e a s i n g . In a p o l i c y environment of d e c r e a s i n g bed supp l y both admi s s ion r a t e s and l eng th s o f s t a y a re d e c l i n i n g s lower than they a re i n c r e a s i n g when bed supp l y i s g e n e r a l l y go ing up. The r e s u l t s suggest t h a t t h i s d i f f e r e n c e i s g r e a t e r w i t h admi s s ion r a t e s than w i t h l e n g t h of s t a y . The r e s u l t s i n T a b l e 28 imp ly t h a t the dec rea se i n bed e f f e c t i s r e l a t i v e l y g r e a t e s t w i t h t o t a l s u r g i c a l u t i l i z a t i o n and, i n p a r t i c u l a r , w i t h SURG A and SURG B type o f i n p a t i e n t s u r ge ry . However, t he se r e s u l t s must be i n t e r p r e t e d w i t h c a u t i o n . The s tudy d e s i g n does not p r o v i d e a b a s i s from which t o conc lude t h a t the dec rea se i n bed e f f e c t when bed supp l y i s g e n e r a l l y d e c l i n i n g i s caused by the dec rease i n bed a v a i l a b i l i t y . The two bed - t ime dummies (BEDSD and BEDSQD) may be c a p t u r i n g a l s o e f f e c t s o f o t h e r t i m e - s p e c i f i c f a c t o r s . Fo r t h i s r e a s o n , a n a l y s e s were c a r r i e d out i n c l u d i n g the t ime dummies i n t o the equa t i on s ( r e s u l t s a re not p re sen ted i n a t a b l e ) . The adjustment f o r the e f f e c t s of t i m e - s p e c i f i c f a c t o r s d i d not a f f e c t the s i z e and s i g n of the BEDSD and BEDSQD c o e f f i c i e n t s i n the e q u a t i o n f o r MED/SURG admi s s i on s , but dec rea sed t h e i r s t a t i s t i c a l s i g n i f i c a n c e . However, the c o e f f i c i e n t on BEDSD remained s i g n i f i c a n t a t 5 p e r c e n t l e v e l . The c o e f f i c i e n t s on BEDS and BEDS 2 remained the same. The c o e f f i c i e n t s on BEDSD 214 and BEDSQD showed the same s i gns f o r MED/SURG days as w i thout the adjustment f o r the t ime dummies/ but i n c r e a s e d i n v a l u e and s i g n i f i c a n c e . The c o e f f i c i e n t s on BEDS and BEDS 2 became a l s o l a r g e r . These r e s u l t s imp ly t h a t the dec rea se i n bed a v a i l a b i l i t y e f f e c t on the o v e r a l l p a e d i a t r i c h o s p i t a l use i n 1975-1982/83, when bed c a p a c i t y was r educed , i s independent of o t h e r t i m e - s p e c i f i c f a c t o r s . However, the adjustment f o r the time-dummies reduced s i g n i f i c a n t l y the s i z e and s i g n i f i c a n c e o f BEDSD and BEDSQD c o e f f i c i e n t s f o r the d i f f e r e n t s u r g i c a l e q u a t i o n s . BEDSD was a c t u a l l y p o s i t i v e and s t a t i s t i c a l l y s i g n i f i c a n t f o r SURG-T&A admiss ions and SURG C admis s ions and days whereas BEDSQD showed n e g a t i v e and s t a t i s t i c a l l y s i g n i f i c a n t r e g r e s s i o n c o e f f i c i e n t o n l y f o r SURG C u t i l i z a t i o n , i m p l y i n g t h a t the bed a v a i l a b i l i t y e f f e c t would have been h i g h e r on SURG C u t i l i z a t i o n i n 1975-1982/83 than i n the e a r l i e r p e r i o d when a c c o u n t i n g f o r the e f f e c t s o f day ca re s u r g e r y use and t i m e - s p e c i f i c con founder s . The c o e f f i c i e n t s on BEDSD and BEDSQD f o r o t h e r s u r g i c a l equa t i ons were s t a t i s t i c a l l y i n s i g n i f i c a n t . E a r l i e r r e g r e s s i o n equat ions i n the poo led 1968-1976 d a t a s e t (Tab le 21) and i n the poo led 1973-1982/83 (Tab le 22) i m p l y lower bed e f f e c t both on MED/SURG and SURG u t i l i z a t i o n i n 1973-1982/83 than i n 1968-1976. These same equa t i on s suggest a l s o a weaker n e g a t i v e a s s o c i a t i o n between DCS and MED/SURG i n the e a r l i e r p e r i o d compared t o l a t t e r . However, 215 the s t r e n g t h o f the n e g a t i v e a s s o c i a t i o n w i t h o v e r a l l s u r g i c a l u t i l i z a t i o n i s the o p p o s i t e . In o r d e r t o examine more c l o s e l y the bed a v a i l a b i l i t y e f f e c t i n r e s p e c t t o i n c r e a s i n g and d e c r e a s i n g bed supp l y two change v a r i a b l e s were c r e a t e d . DELTABED was c a l c u l a t e d as pe rcentage change i n bed c a p a c i t y and DELTAUTIL as percentage change i n m e d i c a l / s u r g i c a l admis s ion r a t e from one y e a r t o the n e x t . A c r o s s - t a b u l a t i o n of DELTABED and DELTAUTIL r e v e a l e d t h a t more s c h o o l d i s t r i c t s i n the poo led d a t a s e t f e l l i n t o n e g a t i v e DELTABED and n e g a t i v e DELTAUTIL c e l l s than i n t o c e l l s i n the o p p o s i t e c o r n e r (both change v a r i a b l e s p o s i t i v e ) , but d i f f e r e n c e s were not v e r y d r a m a t i c . Many s c h o o l d i s t r i c t s f e l l i n t o the o t h e r two co rne r s of the c r o s s - t a b u l a t i o n , more be ing i n the DELTABED+/DELTAUTIL- c o r n e r than i n DELTABED-/DELTAUTIL+ c o r n e r , r e f l e c t i n g a g e n e r a l d e c l i n e i n p a e d i a t r i c h o s p i t a l u t i l i z a t i o n r a t e s , a t l e a s t p a r t i a l l y independent of bed c a p a c i t y changes. Next , a r a t i o of DELTAUTIL t o DELTABED was examined i n those s c h o o l d i s t r i c t s t h a t f e l l i n t o the DELTABED-/DELTAUTIL-c o r n e r of the c r o s s - t a b u l a t i o n and compared t o the same r a t i o i n s c h o o l d i s t r i c t s i n the o p p o s i t e c o r n e r . I f p a e d i a t r i c i n p a t i e n t u t i l i z a t i o n i n c r e a s e s more when bed c a p a c i t y i s i n c r e a s i n g than i t f a l l s when bed supp l y i s d e c r e a s i n g , then one would expect h i g h e r DELTAUTIL/DELTABED r a t i o s f o r s c h o o l d i s t r i c t s where both bed c a p a c i t y and u t i l i z a t i o n a re i n c r e a s i n g than w i t h s c h o o l d i s t r i c t s / y e a r s where both a r e d e c l i n i n g . Examinat ion o f t h i s r a t i o d i d not r e v e a l any s i g n i f i c a n t d i f f e r e n c e s between the two o p p o s i t e c o r n e r s . 217 5. DISCUSSION The main o b j e c t i v e s of t h i s s tudy were t o examine the r e l a t i o n s h i p s between day ca re su r ge ry a v a i l a b i l i t y , h o s p i t a l bed a v a i l a b i l i t y and p a e d i a t r i c i n p a t i e n t u t i l i z a t i o n , w i t h s p e c i a l r e f e r e n c e t o "med i ca l needs" and " s u p p l y " model s . T h i s t h e s i s i s a component i n a b roader at tempt t o examine the economics of p a e d i a t r i c h o s p i t a l s e r v i c e s i n B .C. , and i t c o n t i n u e s the work i n i t i a t e d by o the r s (Evans and Rob inson, 1973; Evans e t a 1., 1978; Evans and Rob inson, 1980; Evans e i a l . f 1983). F i n d i n g s o f t h i s s tudy have importance f o r d e c i d i n g whether the p a e d i a t r i c day ca re su r ge ry program i n B.C. shou ld be expanded, on what grounds, and how, and whether day ca re s u r g e r y i s f u l l f i l l i n g i t s p romi ses . The s p e c i f i c r e s u l t s of t h i s s tudy a r e based on B.C. da ta over the yea r s 1968-1976 and 1981-1983. However, t o the e x t e n t t h a t p a e d i a t r i c h o s p i t a l s e r v i c e s i n B.C. resemble those e l sewhere i n Canada o r Nor th Amer i ca , these f i n d i n g s may be g e n e r a l i z a b l e . T h i s s tudy suppor t s the f i n d i n g s o f h i gh i n t e r - a r e a v a r i a b i l i t y of p a e d i a t r i c h o s p i t a l u t i l i z a t i o n observed i n o t h e r s t u d i e s (Wennberg and Kimm, 1977; C o n n e l l e t a l . f 1981). The v a r i a t i o n among the p a e d i a t r i c p o p u l a t i o n i s much h i g h e r than i n the t o t a l p o p u l a t i o n i n B.C. (Evans e t a l . f 1983). 218 Eighty seven percent of the c r o s s - d i s t r i c t / c r o s s - y e a r v a r i a t i o n i n the o v e r a l l paediatric h o s p i t a l u t i l i z a t i o n could be accounted for by the variables used i n t h i s study. This i s less than what Evans et a l . (1983) explained i n the t o t a l population using s i m i l a r regression models. They reported as high as 92 percent explanatory power for medical/surgical admissions. This i s consistent with Van der Gaag et a l . (1975), who also reported lower explained variance f o r children's' hospital u t i l i z a t i o n than for adult u t i l i z a t i o n . However, a c o e f f i c i e n t of determination of 87 percent i s s u f f i c i e n t l y high to allow the drawing of some conclusions regarding the determinants of paediatric h o s p i t a l i z a t i o n . The study of the e f f e c t of day care surgery a v a i l a b i l i t y on paediatric inpatient u t i l i z a t i o n was based on estimating inpatient u t i l i z a t i o n as i t would have occurred i n the absence of day care surgery. The construction of t h i s hypothetical a l t e r n a t i v e state of the world was achieved by i n c l u s i o n of several factors which may have importance i n determining inpatient u t i l i z a t i o n , into a regression model on the assumption that the e f f e c t of these controlled variables on inpatient u t i l i z a t i o n i s not affected by the existence of day care surgery ( i . e . , no i n t e r a c t i o n e f f e c t s ) . The e f f e c t of the population base i n determining inpatient u t i l i z a t i o n rates, the age-sex d i s t r i b u t i o n of the paediatric population, was c o n t r o l l e d for by age-sex adjustment of the dependent and main independent variables. Other factors that were controlled for 219 i n c o n s t r u c t i n g t h i s a l t e r n a t i v e s t a t e , o r a range of a l t e r n a t i v e s , were p a e d i a t r i c bed a v a i l a b i l i t y , p h y s i c i a n a v a i l a b i l i t y , a v a i l a b i l i t y of p h y s i c i a n s by s p e c i a l t y , a range of socioeconomic c h a r a c t e r i s t i c s of s c h o o l d i s t r i c t s , and unmeasured and unknown time- and d i s t r i c t - s p e c i f i c f a c t o r s . These v a r i a b l e s cover w e l l the range of f a c t o r s t h a t have been r e p o r t e d t o a f f e c t h o s p i t a l u t i l i z a t i o n i n c h i l d r e n . F i n d i n g s on the r e l a t i o n s h i p between day c a r e s u r g e r y a v a i l a b i l i t y and p a e d i a t r i c m e d i c a l / s u r g i c a l and t o t a l s u r g i c a l i n p a t i e n t u t i l i z a t i o n s t r o n g l y support the view t h a t p a e d i a t r i c day care has been l a r g e l y an add-on t o the t o t a l h o s p i t a l c a r e system. I t has generated new o v e r a l l h o s p i t a l u t i l i z a t i o n , i n the sense of h o s p i t a l - b a s e d u t i l i z a t i o n t h a t would not have o c c u r r e d i n the h y p o t h e t i c a l a l t e r n a t i v e no-DCS s t a t e . Although, day c a r e surgery a v a i l a b i l i t y seemed to s u b s t i t u t e f o r i n p a t i e n t care when i t s e f f e c t was s t u d i e d a l one, the r e l a t i o n s h i p was found t o be a s t a t i s t i c a l a r t i f a c t a r i s i n g from the j o i n t i n f l u e n c e of bed a v a i l a b i l i t y on both day c a r e surgery a v a i l a b i l i t y and i n p a t i e n t u t i l i z a t i o n . Day c a r e s u r g i c a l s e r v i c e s have been i n t r o d u c e d more e a g e r l y i n areas w i t h lower bed c a p a c i t y than w i t h a h i g h bed-to-p o p u l a t i o n r a t i o . T h i s r a i s e s the p o s s i b i l i t y t h a t the g e n e r a t i o n e f f e c t a s s o c i a t e d w i t h day c a r e surgery a v a i l a b i l i t y , a f t e r a d j u s t i n g f o r the e f f e c t of bed a v a i l a b i l i t y , r e f l e c t s unmet h o s p i t a l c a r e need due t o i n s u f f i c i e n t h o s p i t a l bed c a p a c i t y . T h i s h y p o t h e s i s i s , 220 however, not suppor ted by the f i n d i n g of a low p a e d i a t r i c ward occupancy r a t e throughout B.C. . Occupancy r a t e s have been d e c l i n i n g i n B.C. s i n c e 1966, and the d e c l i n e has been more marked i n s m a l l p a e d i a t r i c u n i t s (Sheps, 1980). E x i s t e n c e of c a p a c i t y c o n s t r a i n t s on p a e d i a t r i c h o s p i t a l u t i l i z a t i o n i n t h i s s i t u a t i o n can o n l y be imagined i f p a e d i a t r i c wards and h o s p i t a l s were s t a f f e d o n l y f o r low occupancy, i . e . i f the c a p a c i t y c o n s t r a i n t s were s t a f f r a t h e r than the beds themse l ve s . The a v a i l a b l e p h y s i c i a n c a p a c i t y was examined i n t h i s s tudy as a confound ing f a c t o r , but the supp l y of nurses may e q u a l l y w e l l be impor tant and may determine the number of beds a c t u a l l y made a v a i l a b l e from the e x i s t i n g approved bed c a p a c i t y . The q u e s t i o n of whether the observed g e n e r a t i o n e f f e c t of day c a r e su r ge ry i s due t o unmet needs o r n o t , i s not c r u c i a l , however, from a c o s t s a v i n g p e r s p e c t i v e . I f new h o s p i t a l u t i l i z a t i o n i s genera ted , i t means a d d i t i o n a l co s t s whether the new u t i l i z a t i o n i s based on needs o r n o t . An i n c r e a s e i n h o s p i t a l system c a p a c i t y ( i n c l u d i n g day ca re s u r g e r y c a p a c i t y ) would cause the h o s p i t a l based t rea tment of p a t i e n t s w i t h l e s s severe i l l n e s s t h a t were f o r m e r l y t r e a t e d a t home o r i n p h y s i c i a n s ' o f f i c e s . I f these k i n d o f s h i f t s o c c u r , one must always ask whether they improve the outcome of c a r e t o the e x t e n t t h a t i t outweighs the i n c r e a s e d c o s t s and u n d e s i r a b l e e f f e c t s of h o s p i t a l s t a y on c h i l d r e n . F i n d i n g s i n the i n d i v i d u a l year s and i n the poo led 1968-1982/83 d a t a s e t a f t e r adjustment f o r t ime s p e c i f i c confounders 221 suggest t h a t over the p e r i o d 1968-1982/83, l e s s than 10 p e r c e n t of day c a r e su r ge ry r e p r e s e n t e d s u b s t i t u t i o n f o r i n p a t i e n t s u r g e r y and over 90 p e r c e n t appeared t o be g e n e r a t i o n of new a c t i v i t y t o the h o s p i t a l system as a whole. As one might e x p e c t , the s u b s t i t u t i o n seemed t o a f f e c t more na r row ly d e f i n e d i n p a t i e n t su r ge ry c a t e g o r i e s which more c l o s e l y resemble day ca re s u r g e r y - t y p e ca se s . S t a t i s t i c a l l y s i g n i f i c a n t s u b s t i t u t i o n e f f e c t was r e v e a l e d o n l y f o r SURG C-type i n p a t i e n t u t i l i z a t i o n i n the poo led d a t a s e t a f t e r c o n t r o l l i n g f o r p o t e n t i a l confound ing e f f e c t s o f p a e d i a t r i c bed c a p a c i t y , d i f f e r e n t soc ioeconomic c h a r a c t e r i s t i c s o f the s c h o o l d i s t r i c t s and t i m e - and d i s t r i c t - s p e c i f i c f a c t o r s . G i ven the f i n d i n g s t h a t day ca re su r ge ry a v a i l a b i l i t y had no o r s l i g h t l y p o s i t i v e e f f e c t on t o t a l m e d i c a l / s u r g i c a l h o s p i t a l u t i l i z a t i o n and p r a c t i c a l l y no e f f e c t on o v e r a l l s u r g i c a l u t i l i z a t i o n , one can conc lude t h a t p a e d i a t r i c beds which were " s aved " by day c a r e su r ge ry use were f i l l e d w i t h i n c r e a s e d u t i l i z a t i o n by non-DCS e l i g i b l e s u r g i c a l p a t i e n t s and by m e d i c a l c a s e s . T h i s means t h a t p a e d i a t r i c s u r g i c a l u t i l i z a t i o n would have d e c l i n e d more than was a c t u a l l y observed over the s tudy p e r i o d i n the absence of day c a r e s u r g e r y f a c i l i t i e s . G e n e r a l l y d e c l i n i n g p a e d i a t r i c i n p a t i e n t u t i l i z a t i o n and r e l a t i v e l y h i g h unused p a e d i a t r i c bed c a p a c i t y suggest no bed c a p a c i t y c o n s t r a i n t s on i n p a t i e n t use . I t i s p l a u s i b l e t h a t the d i r e c t g e n e r a t i o n of new h o s p i t a l - b a s e d s u r g i c a l a c t i v i t y and i n c r e a s e d p a e d i a t r i c i n p a t i e n t u t i l i z a t i o n through f i l l - i n o f v a c a t e d beds as a r e s u l t of i n t r o d u c i n g day c a r e su r ge ry 2 2 2 f a c i l i t i e s , i n t h i s s i t u a t i o n , r e f l e c t s s upp l y i nduced demand u n r e l a t e d t o m e d i c a l needs. I t i s i m p o s s i b l e , i n t h i s s tudy , t o e s t i m a t e how much o f the g e n e r a t i o n o f new h o s p i t a l - b a s e d a c t i v i t y r e p r e s e n t s a s u b s t i t u t i o n f o r c a re i n p h y s i c i a n s ' o f f i c e s . H i gher p a e d i a t r i c s u r g i c a l u t i l i z a t i o n f a c i l i t a t e d d i r e c t l y by the i n c r e a s e d c a p a c i t y and i n d i r e c t l y by the f i l l -i n of v a c a t e d beds as a consequence of day c a r e s u r g e r y a v a i l a b i l i t y i s not n e c e s s a r i l y an advantage t o a p o p u l a t i o n . H igh s u r g i c a l r a t e s c a r r y w i th them a h i g h r i s k of excess s u r g i c a l deaths (Roos and Roos, 1981). E s t ima te s o f the r e g r e s s i o n c o e f f i c i e n t on day c a r e su r ge ry a v a i l a b i l i t y i n t h i s s tudy d i d not d i f f e r v e r y much from the e s t i m a t e s observed f o r the t o t a l p o p u l a t i o n i n r e s p e c t t o m e d i c a l / s u r g i c a l and t o t a l s u r g i c a l u t i l i z a t i o n , except i n the p o o l e d da ta (Evans e t a 1. f 1983). D i f f e r e n c e s w i t h the poo led da t a c o u l d be e x p l a i n e d by the e f f e c t o f the independent d e c l i n i n g T&A u t i l i z a t i o n over t ime , which i s d i l u t e d a t the t o t a l p o p u l a t i o n l e v e l and does not a f f e c t the r e l a t i o n s h i p between day c a r e su r ge ry and i n p a t i e n t use t o the same e x t e n t as i n the p a e d i a t r i c p o p u l a t i o n . However, t h e r e a r e a l s o s u b s t a n t i a l d i f f e r e n c e s i n the r e s u l t s f o r the day ca re e l i g i b l e s u r g i c a l c a t e g o r i e s . In g e n e r a l , the r e g r e s s i o n c o e f f i c i e n t s on DCS f o r SURG A - C were h i g h e r and the c o e f f i c i e n t o f d e t e r m i n a t i o n was a l s o h i g h e r i n the t o t a l p o p u l a t i o n . The impact of day ca re s u r g e r y on the most narrow 223 day c a r e s u r g e r y e l i g i b l e i n p a t i e n t u t i l i z a t i o n (SURG C) was u n e x p e c t e d l y low i n t h i s s tudy . These d i f f e r e n c e s may be due to a s l i g h t l y d i f f e r e n t c o n s t r u c t i o n of these v a r i a b l e s i n the two s t u d i e s . Evans and c o l l e a g u e s (1983) i n c l u d e d s u r g i c a l p rocedures t h a t had p a r t i c u l a r p o t e n t i a l t o become p o p u l a r i n day c a r e s u r g e r y i n t o the SURG A measure, i n a d d i t i o n t o the top twe lve day c a r e s u r g e r y p rocedures d e f i n e d i n 1976. In t h i s s tudy , o n l y those p rocedures i n the top 30 DCS c a t e g o r i e s t h a t had been per formed a t l e a s t on 40 day c a r e su r ge ry p a t i e n t s i n 1982/83 were i n c l u d e d . The t ime p e r i o d i n the e a r l i e r s tudy (197 6 t o 1968) was a l s o s h o r t e r i n c r e a s i n g the p o s s i b i l i t y t h a t t h e r e have been more changes i n p e r c e i v e d day c a r e s u r g e r y e l i g i b i l i t y over the s tudy p e r i o d i n t h i s s tudy than i n the p e r i o d s t u d i e d by Evans e t a l . . In both s t u d i e s the SURG B measure was c o n s t r u c t e d the same way, a l though the i n c l u s i o n of o p e r a t i v e c a t e g o r i e s was d i f f e r e n t . Only p a t i e n t s w i th l e n g t h of s t a y of l e s s than s i x days were i n c l u d e d . T h i s c u t o f f p o i n t f o r the l e n g t h of s t a y may be too h i gh f o r p a e d i a t r i c day ca re su r ge ry . On the o t h e r hand, the p r o p o r t i o n of day c a r e s u r g e r y - t y p e p a e d i a t r i c i n p a t i e n t s whose l e n g t h of s t a y f a l l s between, f o r example, t h r e e and f i v e days i s i n s i g n i f i c a n t . In the s tudy by Evans e t a l . (1983), i n t e r v i e w e d s p e c i a l i s t s a l l o c a t e d SURG B p a t i e n t s i n t o the SURG C c a t e g o r y by age 224 group. In t h i s s tudy s p e c i a l i s t s d i d not d e f i n e the a l l o c a t i o n by age group but gave a t o t a l e s t ima te of the p r o p o r t i o n of p a t i e n t s t h a t c o u l d have been taken ca re o f i n a day ca re s u r g e r y u n i t . T h i s p r o p o r t i o n was a p p l i e d t o a l l age g roups , which o b v i o u s l y d i s t o r t s the SURG C measure a f t e r age- sex adjustment i f day ca re e l i g i b l e p a t i e n t s were uneven ly d i s t r i b u t e d by age ( e . g . , o l d e r c h i l d r e n were more e l i g i b l e than younger o r v i c e v e r s a ) . T h i s may have caused the l a c k of r e s p o n s i v e n e s s of the SURG C measure t o DCS i n t h i s s tudy . In a d d i t i o n to these measurement d i f f e r e n c e s , the lower response o f day ca re s u r g e r y - e l i g i b l e i n p a t i e n t u t i l i z a t i o n to day c a r e s u r g e r y a v a i l a b i l i t y i n t h i s s tudy may be due to h i g h e r v a r i a b i l i t y of day ca re su r ge ry e l i g i b i l i t y c r i t e r i a a c r o s s s c h o o l d i s t r i c t s and ac ro s s t ime , than f o r the comparable c r i t e r i a f o r a d u l t s . As C o n n e l l e t a l . (1981) have sugges ted , t h e r e may be h i g h v a r i a t i o n of community p r a c t i c e s t y l e s i n r e s p e c t t o p a e d i a t r i c h o s p i t a l i z a t i o n . The f a c t t h a t more of the v a r i a t i o n i n p a e d i a t r i c h o s p i t a l use remained u n e x p l a i n e d than i n t o t a l p o p u l a t i o n h o s p i t a l u se , may r e f l e c t h i g h e r i n d i v i d u a l p r o v i d e r - b a s e d v a r i a t i o n w i t h i n p a e d i a t r i c s . The s m a l l e r p o p u l a t i o n base of s c h o o l d i s t r i c t s i n t h i s s tudy may have i n t r o d u c e d more random e r r o r t o the u t i l i z a t i o n measures, which a l s o c o n t r i b u t e s t o the d i f f e r e n c e between t h i s s tudy and the s tudy i n t o t a l p o p u l a t i o n . 225 R e s u l t s of t h i s s tudy suggest t h a t the low s u b s t i t u t i o n e f f e c t a s s o c i a t e d w i t h day ca re su r ge ry i n the t o t a l p o p u l a t i o n (30-40 p e r c e n t ) (Evans e t a 1. f 1983) does not mask a h i g h e r e f f e c t i n p a e d i a t r i c p o p u l a t i o n . The observed e f f e c t i n t h i s s tudy i s a c t u a l l y lower , i m p l y i n g t h a t t h e r e may be some subgroups i n the a d u l t p o p u l a t i o n f o r whom t h e r e i s a h i g h e r s u b s t i t u t i o n e f f e c t from day c a r e s u r g e r y . T h i s h i g h e r s u b s t i t u t i o n e f f e c t c o u l d be r e l a t e d t o a b o r t i o n s and use of d i l a t a t i o n and c u r e t t a g e (D&C). D&Cs were i n c l u d e d i n the s tudy by Evans e t a l . (1983), and t h e i r expans ion as a day c a r e s u r g e r y p rocedure a f t e r removal o f l e g a l c o n s t r a i n t s may have c o n t r i b u t e d a g r e a t d e a l t o the observed s u b s t i t u t i o n . R e s u l t s of t h i s s tudy g i v e s t r o n g suppor t t o the " supp l y " model . A f t e r a d j u s t i n g f o r age-sex d i f f e r e n c e s , the most power fu l f a c t o r i n d e t e r m i n i n g p a e d i a t r i c h o s p i t a l u t i l i z a t i o n r a t e s was p a e d i a t r i c bed a v a i l a b i l i t y , which e x p l a i n e d a l one n e a r l y 60 p e r c e n t of m e d i c a l / s u r g i c a l h o s p i t a l u se . The c o n s i s t e n c y of the bed e f f e c t from one y e a r t o another and a f t e r adjustment f o r s e v e r a l confound ing f a c t o r s suggests a t r u e c a u s a l r e l a t i o n s h i p between beds and use . The observed bed e f f e c t was g r e a t e r i n the p a e d i a t r i c than i n the t o t a l p o p u l a t i o n (Evans e t a 1 . f 1983), a l though the d i f f e r e n c e was not v e r y marked. D e s p i t e the s t r o n g e r a s s o c i a t i o n i n the p a e d i a t r i c p o p u l a t i o n , the e x p l a n a t o r y power of bed a v a i l a b i l i t y was s u b s t a n t i a l l y lower ( n e a r l y 25 p e r c e n t ) than i n the t o t a l p o p u l a t i o n . The lower c o e f f i c i e n t of 226 d e t e r m i n a t i o n i n the p a e d i a t r i c p o p u l a t i o n may r e f l e c t h i g h e r v a r i a b i l i t y of h o s p i t a l use due to h i g h e r v a r i a t i o n i n i n d i v i d u a l p r o v i d e r s t y l e s . A l s o , g e n e r a l l y lower occupancy r a t e s c r e a t e h i g h e r p o t e n t i a l f o r v a r i a t i o n i n h o s p i t a l use f o r the same bed stock and thus a l l o w more random f l u c t u a t i o n i n p a e d i a t r i c h o s p i t a l use when compared to the t o t a l p o p u l a t i o n . Comparison of the bed e f f e c t i n p a e d i a t r i c and a d u l t p o p u l a t i o n s r e v e a l s t h a t d e s p i t e the low occupancy r a t e i n p a e d i a t r i c h o s p i t a l s , the marginal occupancy r a t e of one a d d i t i o n a l bed would be h i g h e r w i t h p a e d i a t r i c s than i n the t o t a l p o p u l a t i o n . The h i g h e r bed supply e f f e c t i n p a e d i a t r i c p o p u l a t i o n i m p l i e s h i g h e r d i s c r e t i o n i n r e s p e c t t o p a e d i a t r i c h o s p i t a l i z a t i o n . I t a l s o i m p l i e s h i g h e r p o t e n t i a l f o r c o n t r o l l i n g the p a e d i a t r i c h o s p i t a l use by c o n t r o l l i n g the number of a v a i l a b l e beds. However, the r e g r e s s i o n equations i n the pooled d a t a s e t i m p l i e d a lower decrease of i n p a t i e n t u t i l i z a t i o n when t h e r e i s a p o l i c y environment of d e c r e a s i n g bed supply than the r e v e r s e . However, t h i s study c o u l d not c o n f i r m t h a t the observed lower bed e f f e c t was a response t o the d e c l i n e i n bed c a p a c i t y ; t h e r e may be o t h e r f a c t o r s as w e l l . I t can be hypothesized t h a t u t i l i z a t i o n responds more d i r e c t l y t o i n c r e a s e s i n bed supply than t o decreases - i . e . u t i l i z a t i o n i s " s t i c k y downward". However, i t i s p l a u s i b l e t h a t t h i s r e s i s t a n c e r e f l e c t s o n l y a lagged response, and t h a t i n the l o n g e r run u t i l i z a t i o n changes i n response t o bed 227 c a p a c i t y changes would be syrnmetric. In an extreme env ironment of 100 p e r c e n t occupancy, t h i s must be t r u e . More r e s e a r c h would be needed to t e s t these hypotheses . A c c o r d i n g to t h i s s tudy , Roemer's Law a p p l i e s t o p a e d i a t r i c h o s p i t a l u t i l i z a t i o n . The Roemer e f f e c t i s b e l i e v e d t o work through h e a l t h p r o f e s s i o n a l s ' c o n c e p t i o n o f what i s a p p r o p r i a t e f o r h o s p i t a l i z a t i o n . I t assumes t h a t p h y s i c i a n s a re more o r l e s s aware of the a v a i l a b l e bed s u p p l y . The bed s u p p l y , when measured as a b e d - t o - p o p u l a t i o n r a t i o , can be a f f e c t e d i n t h r e e d i f f e r e n t ways: 1) p h y s i c a l bed s t ock i s changed but the p o p u l a t i o n base remains the same; 2) p h y s i c a l bed s t ock remains unchanged but the p o p u l a t i o n base i s changed; and 3) both p h y s i c a l bed s t ock and p o p u l a t i o n base a r e changed. Fo r example, the dec rea se i n b e d - t o - p o p u l a t i o n r a t i o i n 1975-1982/83 was a dec rease both i n a c t u a l p h y s i c a l bed s tock and i n the s i z e of the p a e d i a t r i c p o p u l a t i o n , but w i t h the former b e i n g l a r g e r . The dec rease i n a c t u a l beds v a s t l y exceeded the dec rease i n p o p u l a t i o n i n r e l a t i v e terms. One can h y p o t h e s i z e t h a t p h y s i c i a n s a re more aware of changes i n p h y s i c a l bed s t ock than i n p o p u l a t i o n base and t h a t bed a v a i l a b i l i t y e f f e c t s may be d i f f e r e n t when changes i n the b e d -t o - p o p u l a t i o n r a t i o a re based on changes i n p h y s i c a l bed s tock o n l y compared t o changes o n l y i n the p o p u l a t i o n base . A c l o s e r © x a m i n a t i o n o f t h i s h y p o t h e s i s would a l s o r e q u i r e a sepa ra te s tudy . 228 Soc ioeconomic c h a r a c t e r i s t i c s of a s c h o o l d i s t r i c t were the next most power fu l f a c t o r i n d e t e r m i n i n g p a e d i a t r i c h o s p i t a l u t i l i z a t i o n r a t e s . These f a c t o r s were i n t r o d u c e d t o c o n t r o l f o r p o s s i b l e confound ing e f f e c t s i n r e l a t i o n s h i p s between main s tudy v a r i a b l e s , caused by c h a r a c t e r i s t i c s of i n d i v i d u a l s c h o o l d i s t r i c t p o p u l a t i o n s . S i nce soc ioeconomic da t a were a v a i l a b l e o n l y i n 1971 and i n 1981 i n the r e q u i r e d d e t a i l , v a l u e s of soc ioeconomic v a r i a b l e s i n 1971 were extended to the whole p e r i o d of 1968-1976 and v a l u e s from 1981, t o 1981/82-1982/83, when a n a l y z i n g the poo led d a t a s e t . T h i s e x e r c i s e c o u l d be c r i t i c i z e d as somewhat a r b i t r a r y , because i t imposes c o n s t a n t i n t e r - d i s t r i c t v a r i a n c e and no t ime v a r i a n c e f o r l a r g e t ime b l o c k s . But the f i n d i n g s from the the i n d i v i d u a l y e a r equa t i on s i n 1971 and 1981/82 l e d to the same c o n c l u s i o n s as the p o o l e d d a t a s e t . The t h i r d mean ing fu l f a c t o r i n d e t e r m i n i n g p a e d i a t r i c h o s p i t a l u t i l i z a t i o n r a t e s was p h y s i c i a n a v a i l a b i l i t y by s p e c i a l t y . T o t a l p h y s i c i a n a v a i l a b i l i t y as such d i d not p l a y a r o l e i n p a e d i a t r i c h o s p i t a l i z a t i o n s . The adjustment o f the r e l a t i o n s h i p s between main s tudy v a r i a b l e s f o r the e f f e c t of p h y s i c i a n a v a i l a b i l i t y by s p e c i a l t y d i d not marked ly change the main a s s o c i a t i o n s of i n t e r e s t , i . e . those w i t h bed supp ly and DCS, but improved the c o e f f i c i e n t of d e t e r m i n a t i o n f o r the o v e r a l l e q u a t i o n s . 229 The adjustment f o r d i s t r i c t - s p e c i f i c con found ing e f f e c t s i m p l i e d t h a t t h e r e a re d i s t r i c t - s p e c i f i c p a t t e r n s of p a e d i a t r i c i n p a t i e n t u t i l i z a t i o n , p e r s i s t i n g through t ime , independent of bed and day ca re su r ge ry a v a i l a b i l i t y and of soc ioeconomic f a c t o r s . The adjustment f o r t ime s p e c i f i c dummies con f i rmed t h a t t h e r e a re a l s o t ime s p e c i f i c p a t t e r n s i n p a e d i a t r i c u t i l i z a t i o n , common to a l l s c h o o l d i s t r i c t s . The most c r u c i a l o f these t ime s p e c i f i c e f f e c t s i s the g e n e r a l d e c l i n e i n p a e d i a t r i c h o s p i t a l u t i l i z a t i o n , i n p a r t i c u l a r i n T&A s u r g e r y u se . The s tudy con f i rms t h a t t h i s d e c l i n e has o c c u r r e d i n d e p e n d e n t l y of the i n c r e a s e i n day c a r e s u r g e r y a v a i l a b i l i t y . There has been a g e n e r a l f e e l i n g i n the m e d i c a l community t h a t the s i n g l e o p e r a t i o n of t o n s i l l e c t o m y (wi thout adenoidectomy) i s not s u i t a b l e f o r day c a r e s u r g e r y . However, both adeno idectomies and t o n s i l l e c t o m i e s wi th adeno idectomies a re done i n day c a r e su r ge ry . I f day ca re s u r g e r y had s u b s t i t u t e d f o r i n p a t i e n t T&As, one would have expec ted to see t h i s s u b s t i t u t i o n both i n each i n d i v i d u a l s tudy y e a r and i n the p o o l e d d a t a s e t . T h i s s u b s t i t u t i o n was o n l y observed i n the p o o l e d d a t a , sugges t i ng t h a t i t r e f l e c t s a s t a t i s t i c a l a r t i f a c t due t o the cap tu red g e n e r a l t ime t r e n d . A n a l y s i s of the poo led d a t a s e t t h a t exc ludes T&As w i t h the DCS v a r i a b l e would be needed f o r f i n a l e x c l u s i o n o f the p o s s i b i l i t y t h a t the equa t i on s i n the poo led d a t a s e t r e f l e c t r e a l s u b s t i t u t i o n f o r i n p a t i e n t T&As. However, t h i s was not done i n t h i s s tudy . C o n s t r u c t i o n of an age-sex s p e c i f i c DCS v a r i a b l e w i thou t T&As f o r each s tudy y e a r would have meant c o n s i d e r a b l e a d d i t i o n a l 230 database development. R e s u l t s i n the equa t i on s w i t h t ime s p e c i f i c dummies and i n each i n d i v i d u a l y e a r , t o g e t h e r w i t h the n o t i o n t h a t t o n s i l l e c t o m i e s a re g e n e r a l l y c o n s i d e r e d u n s u i t a b l e f o r day ca re s u r g e r y , were c o n s i d e r e d s u f f i c i e n t e v i d e n c e f o r e x p l a i n i n g the s t a t i s t i c a l l y s i g n i f i c a n t n e g a t i v e day c a r e s u r g e r y e f f e c t i n the poo led d a t a s e t as an a r t i f a c t . The c o n c l u s i o n s of the s tudy a re t h a t day c a r e s u r g e r y a v a i l a b i l i t y i s not c a u s a l l y r e l a t e d t o o v e r a l l p a e d i a t r i c h o s p i t a l i n p a t i e n t u t i l i z a t i o n , but the main d r i v i n g f o r c e beh ind h o s p i t a l u t i l i z a t i o n i n the 0-14 yea r age group i s p a e d i a t r i c bed a v a i l a b i l i t y . Thus, Roemer's law a p p l i e s t o a p a e d i a t r i c p o p u l a t i o n as w e l l . Ques t ions o f the s i z e of the bed e f f e c t when bed supp l y i s i n c r e a s i n g and when i t i s d e c l i n i n g cannot be answered f u l l y i n t h i s s tudy . 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