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Incidence, costs, and compensation of work-related injuries among sawmill workers in British Columbia Alamgir, Abul Hasanat Mohammad 2006

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INCIDENCE, COSTS, AND COMPENSATION OF W O R K - R E L A T E D INJURIES A M O N G SAWMILL WORKERS IN BRITISH COLUMBIA by ABUL HASANAT MOHAMMAD ALAMGIR B.Pharm., University o f Dhaka, 1994 M.Pharm., University o f Dhaka, 1995 M . B . A . , West Texas A & M University, 1999  A THESIS S U B M I T T E D IN T H E P A R T I A L F U L F I L M E N T OF THE REQUIREMENTS  F O R THE D E G R E E OF  DOCTOR OF PHILOSOPHY  in  THE F A C U L T Y OF G R A D U A T E STUDIES (HEALTH CARE AND  EPIDEMIOLOGY)  THE UNIVERSITY OF BRITISH C O L U M B I A A U G U S T , 2006 ©Abul Hasanat Mohammad Alamgir, 2006  ABSTRACT  Objectives: The primary objective o f this study were to investigate the use o f hospital discharge records as a tool for work-related serious injury surveillance, including analyses to compare injury reporting patterns using hospital records versus workers' compensation records and the use o f hospital records to investigate the epidemiology and the economic burden o f serious work related injuries.  Methods: The study population was working members o f the sawmill industry in the Canadian province o f British Columbia between 1989-1998. Hospital discharge records and workers' compensation claims for a cohort o f 5,876 actively employed workers were obtained. Hospitalization records were identified as work-related using I C D - 9 external cause o f injury codes (E-codes) that indicate place o f occurrence, and the responsibility o f payment schedule, which identifies workers' compensation as being responsible for payment. Hospital records were linked and matched to compensation claims by injury diagnosis and available date variables. C l a i m cost information was collected from the provincial compensation agency.  Results: Both the E-code and the payment schedule code available in hospital discharge records were useful i n capturing work-related injuries requiring hospitalization. The study  findings  indicate that the compensation agency underreports serious and acute injuries by about 10%.  u  This study documented that several vulnerable groups o f workers, like, non-white people, and specific injury categories, like, overexertion and falls were related with greater under-reporting. For the cost analyses, the median non-health care costs were $16,559 and healthcare costs were $4,377 per sawmill injury (in 1995 Canadian dollars). B y median costs, the category of fire, flame, natural & environmental was the most costly cause o f injury category. About 9% o f the total costs ($12 million) o f hospitalized injuries were not compensated by the workers' compensation system.  Conclusions Hospital data represent an alternative source o f information for serious work-related injuries. K n o w i n g the injuries and costs that remain unreported and/or uncompensated w i l l be helpful to employers, compensation officials, unions, policy makers and other stakeholders to identify vulnerable worker groups and work processes, and subsequently target preventive measures within an industry.  in  T A B L E OF CONTENTS  ABSTRACT  ii  T A B L E OF CONTENTS  iv  LIST OF T A B L E S  vii  LIST OF FIGURES  —ix  ACKNOWLEDGEMENT  x  CO-AUTHORSHIP S T A T E M E N T S  -xi  CHAPTER 1: INTRODUCTION  1  1.1 F O R M A T OF THESIS  1  1.2 S T U D Y PURPOSE  1  1.3 W O R K - R E L A T E D INJURY  2  1.4 P A T H W A Y OF INJURY A N D ASSOCIATED COSTS  4  1.5 W O R K - R E L A T E D INJURY: S U R V E I L L A N C E  5  1.6 CODING A C C U R A C Y IN A D M I N I S T R A T I V E D A T A S E T S  9  1.7 EPIDEMIOLOGY OF W O R K - R E L A T E D INJURY IN C A N A D A  11  1.8 COST OF W O R K - R E L A T E D INJURY  13  1.9 R E A S E R C H NEEDS A N D S T U D Y JUSTIFICATION  17  1.10 THE MANUSCRIPTS  19  1.11 S T U D Y P O P U L A T I O N A N D D A T A SOURCES  20  1.12 REFERENCES  27  CHAPTER 2: AN EVALUATION OF HOSPITAL DISCHARGE RECORDS AS A T O O L FOR SERIOUS WORK-RELATED INJURY SURVEILLANCE 2.1 INTRODUCTION  -  —  35 35  2.2 METHODS  38  2.3 RESULTS  41  2.4 DISCUSSIONS  44  2.5 REFERENCES  56  CHAPTE R 3: HOW MANY WORK-RELATED INJURIES REQUIRING HOSPITALIZATION IN BRITISH COLUMBIA ARE CLAIMED FOR WORKERS' COMPENSATION? 3.1 I N T R O D U C T I O N -  60 —  —60  3.2 M E T H O D S A N D D A T A S O U R C E S  63  3.3 R E S U L T S  68  3.4. D I S C U S S I O N  70  3.5 R E F E R E N C E S — —  81  CHAPTER 4: ACCURACY OF INJURY CODING IN A CANADIAN WORKERS' COMPENSATION SYSTEM  84  4.1 I N T R O D U C T I O N  -84  4.2 M E T H O D S A N D D A T A S O U R C E S  85  4.3 R E S U L T S  87  4.4 D I S C U S S I O N —  90  4.5 R E F E R E N C E S  96  CHAPTER 5: COSTS AND COMPENSATION OF WORK-RELATED INJURIES IN BRITISH COLUMBIA SAWMILLS  99  5.1 I N T R O D U C T I O N  —  99  5.2 M E T H O D S A N D D A T A S O U R C E S  101  5.3 R E S U L T S  103  5.4. D I S C U S S I O N S  105  5.5 R E F E R E N C E S  114  CHAPTER 6: HOSPITAL COSTS AND COMPENSATION OF TREATING WORKRELATED SAWMILL INJURIES IN BRITISH COLUMBIA  117  6.1 I N T R O D U C T I O N  117  6.2 M E T H O D S  120  6.3 R E S U L T S  123  6.4 D I S C U S S I O N S  124  6.5 R E F E R E N C E S  —  131  v  CHAPTER 7: EPIDEMIOLOGY OF WORK-RELATED INJURIES REQUIRING HOSPITALIZATION AMONG SAWMILL WORKERS IN BRITISH COLUMBIA, 1989-1998  134  7.1 I N T R O D U C T I O N  134  7.2 M E T H O D S A N D D A T A S O U R C E S  -—136  7.3 R E S U L T S  138  7.4 D I S C U S S I O N S  140  7.5 R E F E R E N C E S  CHAPTER 8: DISCUSSIONS AND CONCLUSIONS  -—  153  158  8.1 K E Y F I N D I N G S A N D P O L I C Y I M P L I C A T I O N S  161  8.2 S T U D Y S T R E N G H T S A N D L I M I T A T I O N S  166  8.3 F U T U R E R E S E A R C H  -—171  LIST OF T A B L E S T A B L E 2.1:  E-CODES, I N J U R Y C A T E G O R I E S , A N D M E A N S OF IDENTIFYING WORK-RELATEDNESS  T A B L E 2.2:  D E M O G R A P H I C A N D HOSPITAL C H A R A C T E R I S T I C S OF S T U D Y POPULATIONS  T A B L E 2.3:  -49  —50  IDENTIFICATION OF W O R K - R E L A T E D I N J U R Y H O S P I T A L I Z A T I O N A M O N G T H E F U L L S T U D Y P O P U L A T I O N B Y C A U S E OF I N J U R Y  T A B L E 2.4:  IDENTIFICATION OF W O R K - R E L A T E D INJURY H O S P I T A L I Z A T I O N A M O N G A C T I V E S A W M I L L W O R K E R S B Y C A U S E OF I N J U R Y  T A B L E 3.1:  51  52  I N J U R Y C A T E G O R Y C R E A T E D F R O M ICD-9 C O D E S F O R H O S P I T A L DISCHARGE RECORDS ANDWORKERS' COMPENSATION LAIMS-—75  T A B L E 3.2:  A G R E E M E N T B E T W E E N W O R K - R E L A T E D INDICATORS IN T H E HOSPITAL RECORDS WITH COMPENSATION C L A I M RECORDS FOR FULL STUDY POPULATION AND ACTIVE SAWMILL WORKERS  T A B L E 3.3:  76  I M P O R T A N T D E M O G R A P H I C A N D H O S P I T A L C H A R A C T E R I S T I C S OF THE HOSPITALIZED INJURY RECORDS STRATIFIED B Y C L A I M I N G PATTERN FOR F U L L STUDY POPULATION A N D ACTIVE SAWMILL WORKERS  T A B L E 3.4:  77  A D M I S S I O N C A T E G O R Y A N D C L A I M FILING OF HOSPITALIZED INJURY RECORDS B Y W O R K - R E L A T E D IDENTIFYING INDICATORS FOR F U L L STUDY POPULATION A N D A C T I V E S A W M I L L WORKERS-78  T A B L E 3.5:  INJURY C A T E G O R Y A N D C L A I M FILING OF W O R K - R E L A T E D H O S P I T A L I Z E D INJURIES  79  T A B L E 4.1:  M E A S U R E S OF A G R E E M E N T B E T W E E N C O M P E N S A T I O N  CLAIMS  D A T A A N D HOSPITAL DISCHARGE D A T A B Y N A T U R E OF INJURY-94 T A B L E 4.2:  M E A S U R E S OF A G R E E M E N T B E T W E E N COMPENSATION  CLAIMS  D A T A A N D HOSPITAL DISCHARGE D A T A B Y B O D Y PARTS T A B L E 5.1:  95  C O S T S F O R A L L (173) W O R K - R E L A T E D I N J U R I E S R E Q U I R I N G HOSPITALIZATION A M O N G ACTIVE SAWMILL WORKERS  T A B L E 5.2:  C O S T S B Y C A U S E A N D N A T U R E O F I N J U R Y F O R 173 W O R K - R E L A T E D INJURIES A M O N G A C T I V E S A W M I L L W O R K E R S  T A B L E 6.1:  F O R W O R K - R E L A T E D INJURIES A M O N G  A SAWMILL COHORT  128  COSTS OF HOSPITALIZATION B Y C A U S E A N D N A T U R E OF INJURY (N=173) H O S P I T A L I Z A T I O N S  F O R W O R K - R E L A T E D INJURIES A M O N G  A SAWMILL COHORT T A B L E 7.1:  —111  M E D I A N S T A Y IN HOSPITAL B Y C A U S E A N D N A T U R E OF INJURY (N=173) H O S P I T A L I Z A T I O N S  T A B L E 6.2:  110  129  N A T U R E O F I N J U R Y A N D C A U S E S F O R 173 W O R K R E L A T E D HOSPITALIZATIONS  147  T A B L E 7.2:  N A T U R E O F I N J U R Y A N D B O D Y P A R T S F O R 173 W O R K R E L A T E D HOSPITALIZATIONS 148  T A B L E 7.3:  W O R K - R E L A T E D HOSPITALIZATIONS  A M O N G SAWMILL WORKERS  B Y NATURE, CAUSE A N D B O D Y PARTS INVOLVED T A B L E 7.4:  W O R K - R E L A T E D HOSPITALIZATIONS  B Y JOB CATEGORIES  SAWMILL WORKERS T A B L E 7.5:  149 AMONG -—150  DISTRIBUTION OF W O R K - R E L A T E D HOSPITALIZATIONS B Y JOB CATEGORIES A M O N G BRITISH C O L U M B I A ' S S A W M I L L W O R K E R S  151  LIST OF FIGURES F I G U R E 1.1: S C H E M A T I C D I A G R A M O F I N J U R Y P A T H W A Y  25  F I G U R E 1.2: I D E N T I F I C A T I O N O F A W O R K - R E L A T E D I N J U R Y F I G U R E 2.1:  S T U D Y POPULATIONS FOR A N A L Y S I S OF W O R K R E L A T E D HOSPITALISATIONS  -—  F I G U R E 2.2:  A G E A N D W O R K - R E L A T E D INJURY-  F I G U R E 2.3  AGREEMNT DICHARGE  F I G U R E 3.1:  —26  BETWEEN  TWO  INDICATORS  53 54  OF  THE  HOPSITAL  RECORDS TO IDENTIFY W O R K - R E L A T E D CASES  55  C A S E IDENTIFICATION OF W O R K - R E L A T E D H O P S I T A L I Z A T I O N IN SAWMILL WORKERS  F I G U R E 5.1:  C L A I M O U T C O M E C A T E G O R I E S B Y C A U S E A N D N A T U R E OF W O R K RELATED INJURY  F I G U R E 5.2:  113  C O M P E N S A T I O N OF H O S P I T A L COSTS* B Y T H E W O R K E R S ' COMPENSATION A G E N C Y —  F I G U R E 7.1:  -112  COSTS A N D C O M P E N S A T I O N B Y THE W O R K E R S ' C O M P E N S A T I O N SYSTEM  F I G U R E 6.1:  80  130  DISTRIBUTION OF W O R K - R E L A T E D INJURY R E Q U I R I N G HOSPITALIZATION B Y A G E A M O N G SAWMILL WORKERS  152  ix  ACKNOWLEDGEMENTS  I would like to thank Dr. Paul Demers for providing me with invaluable mentorship and support. Without his guidance it would not be possible for me to complete this work. I would also like to thank the members o f m y supervisory committee: Drs. M i e k e Koehoorn, E m i l e Tompa and Aleck Ostry for their insightful comments and direction throughout this project. I am grateful to all the people who shared their time and knowledge with me along the way, especially: Chris Richardson, Carlo Marra, Weiwei D u , Barbara Karlen, A K M Moniruzzaman, Laurel Slaney, D r . A s l a m Anis, D r . Hugh Davies, Dr. Annalee Yassi, Dr. George Povey, and Dr. Susan Kennedy.  Outside m y academic world, I would also thank m y amazing family, especially: m y parents- Habibur Rahman and Hasina Rahman, wife- Musarrat N a h i d R i m i , m y brothers and other relatives for pushing me to follow m y goals and for providing me with unyielding support and advice from the beginning that gave me necessary strength and motivation to begin and complete this work. Without their many compromises, dedication and commitment, none o f this would have been possible. M y friends- Zohra Akhter, Dr. M a t i u l A l a m , D r . Hafiz G A Siddiqi, Dr. A N M Meshquatuddin, Sayez Rahim, M o l l a Mohammad M a z n u , Alamgir Kabir, and Joanne Palin were also very helpful. Finally, I express gratitude to G o d who gave me the mental strength during this entire period.  This research was supported by grants from W o r k S a f e B C (Workers' Compensation Board o f British Columbia). In addition, D r . Paul Demers and D r . Clyde Hertzman supported me with research assistantship.  x  CO-AUTHORSHIP STATEMENTS  The candidate is first author on all the manuscripts; he developed the study questions, entered and manipulated the data, performed statistical analyses, and wrote the final manuscripts. C o authors o f the study include Paul A Demers, M i e k e Koehoorn, A l e c k Ostry, and Emile Tompaall members o f the supervisory committee.  xi  CHAPTER 1 INTRODUCTION  1.1 FORMAT OF THESIS This doctoral dissertation utilizes a manuscript-based format approved by the Faculty o f Graduate Studies at the University o f British Columbia ( U B C ) . Following the recommendations of the Faculty o f Graduate Studies at U B C , this dissertation begins with an introduction and literature review o f the overall program o f research ending with the thesis objectives for each manuscript. The second section is composed o f the individual manuscripts, each o f which includes a literature review, statement o f research  objectives, results, discussions and  conclusions. The last section o f the dissertation is a concluding chapter that contains a brief review o f the findings reported i n the manuscripts followed by a discussion o f the implications o f the research findings in terms o f the overall program o f research, and some comments on areas for future research. A m o n g the six papers that are presented here, two are already published i n peer reviewed journals and the remaining four are under review for publication.  1.2 STUDY PURPOSE The purpose o f this doctoral dissertation is to present a program o f research centred on the surveillance o f work-related injury using hospital discharge data among a cohort o f sawmill workers in the Canadian province o f British Columbia ( B C ) , including using these records to investigate injury reporting patterns relative to claim data, and the economic consequences and epidemiology o f serious injuries. The dissertation includes a series o f independent but related  1  chapters that describe the results o f the following six studies/papers: a) an investigation o f the validity o f hospital discharge records as a tool for work-related serious injury surveillance, b) a comparison o f the reporting patterns o f workers' compensation system with that o f hospital discharge records, c) an assessment o f the validity o f injury coding patterns o f workers' compensation  records  compared  to hospital discharge  records,  d) an estimation  o f the  compensation costs o f work-related serious injuries e) an estimation o f the hospitalization costs o f work-related serious injuries, and f) an epidemiological investigation o f work-related sawmill injuries requiring hospitalization. The dissertation ends with a summary and discussion o f the key research findings and provides some guidelines for future research directions in terms o f the outlined program o f research.  1.3 W O R K - R E L A T E D I N J U R Y Work-related injury not only results i n suffering and economic burden for the worker and family but also adds to the overall cost to society through lost productivity and increased use o f health and welfare services. The International Labor Organization (ILO) states that there are two million work-related deaths worldwide every year which translates into more than 5,000 fatalities per day. According to I L O , for every fatal injury there are around another 500 to 2,000 injuries [ILO, 2002]. Leigh and colleagues [1999] estimated that approximately 100 million occupational injuries including 100,000 deaths occur in the world annually. A n injury is an act that hurts, damages, or results in a sustained loss [Merriam-Webster, 2005]. Injuries are classified as being acts o f unintentional or intentional physical damage that result from the transfer o f energy [Peek-Asa and Zwerling, 2003]. The types o f energy transfer that cause injuries are: •  Mechanical or kinetic energy (e.g., fall)  2  •  Electrical energy (e.g., electrocution)  •  Thermal energy (e.g., burns)  •  Chemical energy (e.g., poisoning)  •  Absence o f essential energy (e.g., suffocation) A work-related injury is defined by the workers' compensation system as one that arises  out o f or in the course o f employment or is due to the nature o f employment [Workers' Compensation Board ( W C B ) , 2006]. Thus, in countries which have some sort o f compensation systems in place, a worker must have been working when hurt and the injury must have been caused by something to do with the job in order to receive compensation [ W C B , 2006]. A s a consequence o f injury, impairments, functional limitations, and disabilities can happen to the injured employee. A n impairment refers to a physiological or anatomical loss or abnormality. A n impairment may in some cases give rise to a functional limitation, defined as a restriction o f a person's capacities. Lastly, functional limitations may i n some cases lead to a disability i f they limit the person's ability to engage in activities at home, work, and/or society [Weil, 2001] [Figure 1.1]. In the last five years (2000-2004) there were 5,027,061 work-related compensation claims reported throughout Canada resulting in an average yearly count o f 1,005,412 claims [Association o f Workers Compensation Boards o f Canada, ( A W C B C ) , 2006]. In British Columbia, Canada, data obtained from the provincial compensation agency indicates that over 822,018 time-loss claims were submitted from 1997 to 2004 averaging about 164,404 per year [ A W C B C , 2006]. The top 4 injuries in this province for 2000-2004 by time-loss claims were strains (97,390), back strains (79,230), cuts (35,390), and contusions (33,970) and the top 4 injuries by days lost were strains (5.1 million days), back strains (3.4 million), fractures (2.3  3  million), and contusions (0.8 million) [ W C B , 2004]. Over the past ten years, an average o f 151 fatal claims has been accepted for compensation annually in the province o f British Columbia [ W C B , 2004]. From 1993 to 1997, the average accepted, time-loss claim rate was 7 injuries per 100 full-time equivalent workers in B C sawmills compared to the overall provincial average o f 5.4 injuries [ W C B , 1999].  1.4 P A T H W A Y O F I N J U R Y A N D A S S O C I A T E D C O S T S The field  o f injury prevention has provided some  solution-oriented models  for  understanding the hazards. The Haddon matrix, developed by W i l l i a m Haddon, has been used in injury prevention research and intervention [Runyan, 1998; Runyan, 2003]. The Haddon matrix is a grid where the rows represent different phases o f an injury (pre-event, event, and postevent), and the columns represent different influencing factors (host, agent/vehicle, physical environment, social environment). The host column represents the person or persons at risk o f injury. The agent o f injury impacts the host through a vehicle (inanimate object) or vector (person or other animal/organism). Physical environment refers to the actual setting where the injury occurs. Socio-cultural and legal norms o f a community constitute the social environment. The phases o f an event are depicted on the matrix as a continuum beginning before the event (pre-event), the event itself (event phase), and sequelae o f the event (post-event phase). The objectives o f this thesis oriented around identifying the injury and its' costs, rather than investigating its causes. Figure 1.2 provides a framework o f the approach taken by this thesis toward injury identification. A work-related injury might or might not be claimed for compensation. Those that reach hospitals can be identified by the work-related indicators available in the hospital discharge records, but, injuries that do not reach hospitals w i l l be  4  beyond the scope o f this investigation. This thesis w i l l also not be able to assess the impact o f non-work related injuries that are claimed for compensation.  1.5  W O R K - R E L A T E D INJURY: SURVEILLANCE Monitoring and surveillance o f injury helps to estimate the size o f a problem;  characterize injury trends; design, implement and evaluate preventive programs; improve knowledge o f injury among health professionals, policy makers and public; and identify research needs [Kaucke, 1988]. Workers' compensation claims data represents an important source o f information on work-related injuries. In a review i n 1998, Goldsmith [1998] recommended the use o f workers' compensation data for epidemiologic research. H e assessed several studies based on data extracted from workers' compensation or disability programs and recommended that valuable information could be derived from it. However, it is important to keep in mind that the workers' compensation agencies reports do not usually include all workplace injuries: they only include compensated time-loss injuries. The A W C B C ( A W C B C )  defines a time-loss injury as "an injury for which a worker is  compensated for a loss o f wages following a work-related injury or receives compensation for a permanent disability with or without time lost in his or her employment" [ C C O H S , 2006]. Injury cases not reported to or accepted by a workers' compensation agency or injuries among some work groups that are not covered by the compensation agency (such as the self-employed) might not be included in the published reports. Azaroff  and colleagues  [2002] thoroughly investigated the reporting patterns o f  occupational injury in U S A by the Bureau o f Labor Statistics, workers' compensation wagereplacement documents, physician reporting systems, and medical records o f treatment charged  5  to workers' compensation. They explained how cases can be lost at successive steps o f documentation. Their findings point out that workers constantly risk unfavourable consequences for attempting to report such injuries. Though workers' compensation system should ideally cover healthcare, disability and rehabilitations costs, a number o f studies have uncovered that workers often are not covered by it, do not report all injuries or illness, or do not receive adequate compensations. Waller and colleagues [1989] studied injuries to carpenters in Vermont and calculated hospital costs for injuries. They found that only one third o f payment came from workers' compensation. Frumkin and colleagues [1995] characterized occupational injuries from injury registry in emergency departments i n a poor inner-city population. Only about one quarter received workers' compensation. Stanbury and colleagues [1995] studied patients  with confirmed silicosis  identified by the silicosis surveillance program i n the N e w Jersey Department o f Health from 1979 through 1992. Only 3 1 % o f these patients stated that a claim had been filed and 84% o f those whose claims were settled were awarded payments. Biddle and colleagues  [1998]  estimated the rate at which workers suffering from occupational illnesses file for workers' compensation lost wage benefits. They matched a database o f reports o f known or suspected cases o f occupational illness with workers' compensation claims data. Overall, between 9% and 45% o f reported workers filed for benefits. Women and employees o f small firms were more likely than others to file for worker's compensation and filing rates were found to vary considerably across industries and diagnostic categories. Rosenman and colleagues [2000] i n a cross-sectional study o f unionized autoworkers  individuals diagnosed with neck,  upper  extremity, and low back work-related musculoskeletal disease found that only 25% o f workers with a work-related musculoskeletal condition filed for workers' compensation. The strongest  6  predictors o f filing were severity o f the condition, length o f employment, annual income, and worker dissatisfaction with coworkers. Some Canadian researchers have also investigated this issue. Shannon and Lowe [2002] in a Canadian survey reported that among 143 eligible injuries, 40% had not filed a workers' compensation claim. Severity o f injury was the strongest predictor o f claiming according their study. Kraut [1997] estimated the extent o f occupational disease morbidity and mortality i n Canada by comparing and contrasting four different data sources: Canadian National Workers' Compensation  Boards  Statistics, U . S . Bureau o f Labor Statistics  Workforce, California Physician's First Reports adjusted proportionate  adjusted  to  Canadian  to the Canadian Workforce, and  model o f overall disease incidence obtained through literature review. He  concluded that each data source was limited in its ability to provide a true estimate o f the extent o f morbidity and mortality due to occupational disease in Canada. -^Researchers and stakeholders have investigated the use o f other data sources for injury surveillance. Layne [2004] provided an analysis o f similarities and differences in two different data sources used for the study o f occupational injury mortality in the United States from 1992 to 1997: The National Traumatic Occupational Fatalities surveillance system and the Census o f Fatal Occupational Injuries. They found each system to vary in methodology, leading to different census counts. Biddle and Marsh [2002] compared the same two national systems that compile fatal occupational injury data i n the United States, and evaluated counts for the nation and by state for worker and case characteristics. They recommended use o f multiple data sources for comprehensive injury surveillance. Murphy and colleagues [1996] described the strengths and weaknesses o f six data collection systems that record occupational injuries and illnesses in U S A on a national level, and compared the leading estimates from these systems for 1990. They  7  concluded that all occupational health databases have limitations when used to summarize the national scope o f workplace hazards and a comparison o f data from multiple sources might produce more credible estimates. Work-related injury is greatly under-reported  i n the informal sectors. For example,  traditional worksite injury surveillance methods are often ineffective for farms employing seasonal labor. M a n y small farms are exempt from mandatory injury reporting and a high proportion o f foreign workers and the temporary nature o f the work further discourage reporting. Earle-Richardson G and colleagues [2003] used anonymous medical chart data from migrant health centers and regional hospital emergency rooms to account for the work-related events in such places. Canada, with a high proportion o f immigrants, may have groups that underutilize social services and underreport workplace injuries. Alternate sources o f data may capture these work related injuries, such as medical services visits or hospitalizations. There remains a need to investigate different sources o f work-related injury surveillance tools and compare these. There is evidence to suggest that a combination o f data sources may provide a more comprehensive picture. Yager and colleagues  [2001] developed a pilot  occupational injury and illness database that incorporated and standardized data across a number o f companies o f differing sizes and configurations. They favored aggregation o f relevant health and safety data across companies to improve statistical power for the assessment o f rare injuries within a sector. Oleske and Hahn [1992] combined administrative and clinical data from a network o f occupational medicine clinics to evaluate the utility o f these data in the surveillance o f non-fatal occupational injuries. They recommended that a surveillance system based upon ambulatory care data can be a feasible method for identifying priority areas for the prevention o f work-related injuries. Brewer and colleagues [1990] described experience o f a clinic-based  8  occupational injury surveillance system involving occupational medicine clinics. Their results supported the feasibility o f conducting clinic-based occupational injury. Liss and colleagues [1997] explored the use o f hospital records for occupational diseases and concluded that it was an underutilized source. Noe and colleagues [2004] demonstrated the use o f an emergency department as a data source for work-related injuries in Nicaragua because it captured both the formal and informal workforce injuries. Therefore, the use o f some clinical databases may hold promise for workplace injury surveillance and other research. In summary, we rely heavily on compensation claim data which may underreport workrelated injuries; and studies suggest a combination o f data sources for a more comprehensive picture. However, limited evidence is available on which data sources to use and their validity/reliability, although some clinical data sources hold promise.  1.6  CODING ACCURACY IN ADMINISTRATIVE DATASETS Coding accuracy is a serious concern for any database system and for epidemiological  researchers using such data. The increased use o f administrative and aggregated data in epidemiological research further underscores the significance o f coding accuracy and data validation. The use o f external sources for case identification and case validation are two ways o f investigating data quality and validity o f results. Administrative health data usually originate from administering health care services, enrolling members into health systems/ insurance plans, and reimbursing for services. The primary producers o f administrative data are the health care providers and private health care insurers. Administrative data are readily available, inexpensive to acquire, computer readable, typically encompass large populations, and suitable for longitudinal analysis. The use o f administrative data is based, however, on the assumption that it provides reasonably valid information on injury or disease diagnoses. Evaluation o f the  9  validity o f these datasets is vital to use them for epidemiological investigations and surveillance purposes. A number o f studies examining the accuracy o f diagnosis codes i n such datasets has been published. Langley and colleagues [2006] studied the level o f accuracy i n coding for injury principal diagnosis and the first external cause code for public hospital discharges in N e w Zealand for the period 1996-1998. They recommended that users o f that data can have a high degree o f confidence in the injury diagnoses coded under the International Classification o f Diseases, 9th Revision, Clinical Modification ( I C D - 9 - C M ) . Farhan and colleagues [2005] reviewed medical records from patients at a Saudi Arabia hospital following the guidelines o f I C D - 9 - C M for accuracy and completeness o f documentation and coding o f primary and secondary diagnoses and procedures performed. O f the items abstracted, 70% were assigned a correct code according to their investigation. Neale and colleagues [2003] aimed to assess the interrater reliability o f coding in the Queensland Trauma Registry in Australia. Interrater agreement between coders was high for external cause, intent, and place o f injury. Agreement between the raters for Injury Severity Score was found to be very high. The accuracy o f coding in the Queensland Trauma Registry was sufficiently high to ensure that quality data were available for research, audit and review. L e M i e r M and colleagues [2001] evaluated the accuracy o f external cause o f injury codes (E codes) reported in computerized hospital discharge records. According to them, the detail codes (complete E codes) reported i n hospital discharge codes were less reliable and must be used with caution. Macintyre [1997] aimed to ascertain the reliability o f injury data in the Victorian inpatient database in Australia. Nearly half the errors in the principal diagnosis were minor, involving the last two digits. External cause codes were more complete than diagnosis  10  codes. Thus, they found the use o f the principal-diagnosis code and E-codes for injury surveillance to be feasible and reliable. Evaluation o f the validity o f codes o f the work-related injury surveillance tools is vital because safety interventions at workplaces are often based on reports generated from these data sources.  1.7  EPIDEMIOLOGY OF WORK-RELATED INJURY IN CANADA Occupational epidemiology identifies the demographic and work-related risk factors  associated with work-related injury, describes the injuries, and provides important clues as to where  and how interventions measures can be undertaken.  Epidemiological studies  on  occupational injury i n Canada are limited i n number relative to other health outcomes. A few studies have identified common injury categories i n different industrial sectors and investigated injury incidence b y work group and tasks that should help guide future prevention efforts. Pickett and colleagues [1999] used a national registry for the surveillance o f fatal farm injuries to describe these injuries and compare rates with those in other industries. The leading mechanisms o f fatal injury were tractor rollovers, blind runovers, extra-rider runovers, and entanglements i n machinery. Compared with other industries, agriculture was found to be the fourth most dangerous i n Canada in terms o f fatal injury, behind mining, logging and forestry, and construction. Saar and colleagues [2006] described the incidence and nature o f farm-related deaths and injuries i n British Columbian farms from 1990-2000. After analyzing farm fatalities and farm injury hospitalizations data, they found higher rates o f non-machinery-related injuries resulting in hospitalizations among young adult B C farmers.  11  Yassi and colleagues [2005] studied time-loss claims data for 1992-2002 from the workers' compensation agencies in Canadian healthcare workplaces. According to their findings, musculoskeletal injuries consistently comprised the majority o f time-loss claims i n this sector. Needlestick injuries, infectious diseases and stress-related claims infrequently resulted in timeloss claims. Sibley and colleagues [2005] studied the epidemiology o f occupational injuries experienced by Canadian rotor-wing health care providers. The frequent cases were for hand lacerations, leg contusions and acute back injuries. Overall, an injury rate o f 3.2 injuries per person per year was reported. Lifting was cited as a common factor in injury. Choi and colleagues [1996] investigated patterns and risk factors for sprains and strains in Ontario in 1990 using Ontario workers' compensation data. With respect to occupations, nurses and truckers had a higher-than-expected  risk. Overexertion, bodily reaction from  involuntary motions, running and stretching, and slippery surfaces were associated with a high risk o f occurrence o f sprains and strains. Breslin and colleagues [2006] identified risk factors o f work injuries among Canadian adolescents and young adults, and examined provincial differences in medically attended work injury rates. Saskatchewan youth were about twice as likely to be injured at work compared to Ontario youth. A l l jobs showed higher risk than administrative clerical jobs, and visible minorities, students, and 15-17 year olds had a reduced likelihood o f work injury than their counterparts. Barroetavena [2001] in an epidemiologic investigation o f injury mortality among sawmill workers i n British Columbia found the overall fatality rate to be 18.1 per 100,000 person-years for the period o f 1950-1990. Machine operators and mobile equipment operators were the occupational groups with the highest crude fatality rates. Over 80% o f the deaths were caused by  12  severe trauma to the head, spinal cord, or multiple sites. This study and the current thesis have used the same cohort o f sawmill workers. There are limited studies o f non-fatal injuries in Canada; differences in injury risk and rates by work group and work tasks need to be investigated in Canadian context.  1.8  C O S T O F WORK-RELATED INJURY Cost o f illness/injury (COI) studies are important for providing information on 1) the  economic burden o f injuries; 2) the comparison o f economic burden by disease or condition; 3) the cost to be incorporated into cost-effectiveness analysis; 4) the most important components o f specific injuries warranting research on treatment options and prevention efforts; 5) the trends in costs and projection o f future costs; and 6) evidence based decision making for prevention resource allocation [Koopmanschap, 1998]. Some economic costs o f workplace injury and illness are readily evident (Figure 1.1). These include medical costs, lost time at work, and the administration o f programs for those injured. Others, however, are not that easy to quantify: the loss o f life, changes in the future work activity and earnings o f the injured, impacts on households o f injured or i l l workers, diminishing quality o f life [Weil, 2001]. Different points o f view (perspectives) can also lead to different cost estimates. The society's perspective considers costs to all sectors o f society. The government's perspective considers costs to the government only, such as costs to the health care and justice systems. The health care providers' perspective considers costs imposed on various types o f hospitals, health maintenance organizations, and other health care providers [Choi and Pak, 2002; Drummond, 1997].  13  A study published in 1998, estimated that the total cost o f intentional and unintentional injuries i n Canada was greater than $12.7 billion per year or 8% o f the total direct and indirect costs o f illness ranking fourth after cardiovascular disease, musculoskeletal conditions and cancer [Health Canada, 1998]. This study estimated that unintentional injuries alone cost Canada more than $8.7 billion annually. More than $4.2 billion o f the total is i n direct cost to the health care system and approximately $4.5 billion is the indirect cost o f loss o f productivity due to impairment, disability and premature death. [Health Canada, 1998]. When injuries involve an employed segment o f the society, the costs are usually a lot higher. In the province o f British Columbia, a total o f 2.8 million days were lost from work due to work-related injury in 2004 and the claim costs for only year 2004 was $12,166 million [ W C B , 2004]. Costs o f occupational injury studies i n Canada are scarce or non-existent. Locker et al. [2003] estimated the economic burden o f agricultural machinery injuries that occurred in Ontario, between 1985 and 1996. The total economic burden o f these injuries over the 12-year study period was estimated to be $228.1 million, or $19.0 million annually (1995 Canadian dollars). B y extrapolation, the economic burden o f all farm injuries in Canada was estimated by them to be between $200 and 300 million annually. There are a handful o f such studies published i n the U S A . Some studies have estimated costs within industrial sectors. Waehrer and colleagues [2005] studied costs o f occupational injury and illness within the health services sector using 1993 nonfatal incidence data drawn from the Bureau o f Labor Statistics Annual Survey. Medical costs were from the claims information, productivity (wage) costs were calculated using the Current Population Survey and pain and suffering costs were estimated from data on jury verdicts. Costs o f injuries and illnesses were to nursing aides and orderlies US$2,200 million; to registered nurses US$900 million and  14  for licensed practical nurses U S $40 million. Leigh and colleagues [2001] estimated the costs o f job-related injuries i n agriculture in the United States for 1992. The authors reviewed data from national surveys to assess the incidence o f fatal and non-fatal farm injuries. Agricultural occupational injuries cost an estimated $4.57 billion in 1992. Direct costs are estimated to be $1.66 billion and indirect costs, $2.93 billion. Leigh and colleagues [2004] ranked industries using total costs and costs per worker. Cost data were derived from workers' compensation records, estimates o f lost wages, and jury awards. The following industries were at the top for average cost (cost per worker): taxicabs, bituminous  coal  and lignite mining,  logging,  crushed stone,  o i l field  services, water  transportation services, sand and gravel, and trucking. Industries high on the total-cost list were trucking, eating and drinking places, hospitals, grocery stores, nursing homes, motor vehicles, and department stores. A few others have tried to estimate costs by states and national level. Waehrer and colleagues [2004] also estimated occupational injury and illness costs per worker across states. Analysis was conducted on injury data from the Bureau o f Labor Statistics and costs data from workers' compensation records. In the state o f Washington, the costs o f nonfatal cases with at least 1 day o f work loss per employee was $864, whereas, the total costs for non-fatal cases were $1,241 million and the total costs for fatal cases were $317 million. Presence o f sectors like farming, agricultural service, forestry, fishing, mining, transportation and public utilities were important in explaining the high costs across states. M i l l e r and Galbraith, [1995] estimated the costs o f occupational injury in the United States using national expenditure data. Overall, workplace injuries cost the U . S . an estimated $140 billion annually. This estimate includes $17 billion in medical and emergency services, $60  15  billion in lost productivity, $5 billion i n insurance costs, and $62 billion in lost quality o f life. Leigh and colleagues [1997] estimated the total direct ($65 billion) plus indirect ($106 billion) costs annually in the civilian American workforce using national and large regional data sets collected by the Bureau o f Labor Statistics, the National Council on Compensation Insurance, the National Center for Health Statistics, the Health Care Financing Administration, and other governmental bureaus and private firms. A few studies estimated costs by states. Neumark and colleagues [1991] estimated the annual economic costs o f occupational injuries and illnesses i n Pennsylvania in 1988: foregone earnings costs resulting from occupational injuries and illnesses were estimated at between $1.22 billion and $2.02 billion and estimates o f medical costs ranged from $740 million to $797 million. Leigh and colleagues [2001] estimated costs associated with occupational injuries and illnesses i n California in 1992. They aggregated and analyzed national and California data sets collected by the U . S . Bureau o f Labor Statistics, California Workers' Compensation Insurance Rating Bureau, California Division o f Industrial Relations, the National Center for Health Statistics, and the U . S . Health Care Financing Administration. The direct costs were $7.04 billion and the indirect costs were $13.62 billion. Injuries cost $17.8 billion (86%) and illnesses $2.9 billion (14%). Most o f these cost studies acknowledged that their estimates were likely to be low because they ignored such costs as pain and suffering and home care provided by family members, and because the numbers o f occupational injuries and illnesses were likely to be underreported by the data sources. Most o f the costs o f injury studies are done i n the U S A , and the U S A has different health care system and social safety nets from Canada.  16  1.9 RESEARCH NEEDS AND STUDY JUSTIFICATION Hospital discharge records represent a readily existing source o f data for the monitoring of severe injuries. These records have information on the nature, cause and severity o f injuries, and are collected autonomously outside o f the contentious arena o f attribution. Despite their potential to capture work-related injury, little research has been carried out on their validity and completeness. In Canada, a few studies have attempted to identify work-related events using hospital discharge records, but have focused on capturing a specific range o f events, such as those related to agricultural machineries, or occupational asthma [Dimich-Ward et al., 2004; Locker et al., 2002, Liss et al., 2000]. Hospital discharge records have the potential to be a valuable data resource for surveillance because o f the comprehensive public health care system in Canada. Once hospital discharge records can be established as a potential tool for severe non-fatal injuries, the next logical step should be comparing and contrasting it with the workers' compensation claims to examine the agreements between these two sources. Hospital dataset w i l l never capture all injuries, but it w i l l provide a great comparison tool as people would expect the work-related hospitalizations to be compensated. Epidemiologic study o f work-related injuries has been stalled by the lack o f a comprehensive and independent reporting system. A m o n g the information sources available, workers' compensation systems are currently considered a major surveillance tool. However, documented underreporting o f work-related injuries by the workers' compensation systems has led to an interest in exploring different sources o f information for use. If hospitalization records can be established as a surveillance tool for serious injuries, this can be used alone and i n conjunction with the workers' compensation data to act as a more comprehensive and reliable  17  source of injury information. Epidemiologic studies based on these new surveillance tools will provide new information which can be incorporated into health and safety interventions. Workers' compensation data have been used by health services and population health researchers to study the epidemiology, outcomes, and costs of work-related injury, and also to examine the value of the services provided by the compensation systems. The use of workers' compensation data for research purposes is based, however, on the supposition that it provides realistically valid information on injury diagnoses. Evaluation of the validity of the workers' compensation system dataset is vital because this data source provides the most commonly used source of information on work-related injuries to date. Hospital discharge records provide a new source to compare the validity of important diagnosis codes in the compensation systems reports. Most of the cost statistics on work-related injury in Canada have been based on official reports from workers' compensation agencies, but these agencies do not capture all workrelated injury nor do they cover all associated costs. Therefore, it is invaluable to study costs using injury reports from an independent and different surveillance source to obtain a more complete account of serious injuries. Additionally, estimating costs using an independent source and comparing the findings with the results reported by the workers' compensation systems will reveal the magnitude of the burden shifted to other social safety systems. [Appendix-2: Diagram on Work related injury identification]  18  1.10 T H E MANUSCRIPTS  1.10.1 FIRST PAPER The first paper o f this thesis identifies and describes work-related serious injuries among sawmill workers in British Columbia, Canada using hospital discharge records, and compares the agreement and capturing patterns o f the work-related indicators available i n the hospital discharge records.  1.10.2 SECOND PAPER This chapter investigates the concordance between hospital discharge records and workers' compensation records for work-related serious injuries among this cohort o f sawmill workers. It also examines the extent to which workers' compensation capturing patterns vary by cause, severity o f injuries, and demographic characteristics o f workers.  1.10.3 THIRD PAPER This part o f the study assesses the validity o f injury related diagnostic codes in the British Columbia's workers' compensation agency's dataset using a hospital discharge dataset as the comparative standard. Hospital records are matched to the compensation records for each injury record and the levels o f agreement by injury category are examined.  1.10.4 FOURTH PAPER This chapter evaluates the costs o f work-related injury in this cohort o f sawmill workers and describes the costs not compensated by the workers' compensation agency. For each work-  19  related injury category, the median and total non-health care costs and healthcare costs are determined.  1. 10.5 FIFTH PAPER This study estimates the hospital costs o f treating work-related injury among the cohort o f sawmill workers i n British Columbia. The median stay i n hospitals i n days and the ^median hospital costs are presented. The total hospital costs for all the work-related injuries as well as proportion o f total hospital costs that the provincial compensation agency does not compensate are estimated.  1.10.6 SIXTH PAPER The  goals o f this investigation are to describe work-related injuries requiring  hospitalization by cause, nature, and body parts for a ten-year period among the sawmill workers and identify the job categories and demographic characteristics that are associated with higher risk o f sustaining wok-related injury.  1.11 STUDY POPULATION AND DATA SOURCES  1.11.1 T H E SAWMILL INDUSTRY In the province o f British Columbia, about 30,000 workers (2% o f the workforce) were working i n the logging and forestry industry during the study period o f 1993-1998 [ B C Statistics, 2004]. Sawmills and other lumber mills are hazardous work environments due to the nature o f the work processes, the types o f equipment used, and materials handled [Demers and  20  Teschke, 1998]. From 1993 to 1997, the average accepted, time-loss claim rate was 7 injuries per 100 full-time equivalent workers in B C sawmills compared to the overall provincial average o f 5.4 injuries [ W C B , 1999]. From 1993 to 1997, the W C B paid more than $325 million for claims in forest products manufacturing. There were 41,932 health-care-only claims costing a total o f $11.5 million, 23,800 time-loss (short term disability, and long term disability) costing $297.4 million, and 35 fatalities costing $10.9 million [ W C B , 1999]. Therefore, the sawmill industry i n British Columbia represents an important workplace setting to investigate the use o f hospital discharge records for work-related injury surveillance and costs o f such injury because o f its hazardous work environments and importance to the local economy.  1.11.2 DATA SOURCES For this study, two administrative datasets from the British Columbia Linked Health Database ( B C L H D ) - the workers' compensation claims and hospital discharge records - were used. The demographic and work-history data were already collected on the study population using employee records as part o f previous studies. Additionally, claim costs from the workers' compensation system were collected, and the standard hospital billing chart from the Health Ministry was used for the cost analysis. Access to the full set o f data was gained mainly through the B C L H D maintained by the Centre for Health Services and Policy Research at the University o f British Columbia.  1.11.3 T H E STUDY POPULATION The B C Sawmill Cohort originally included 28,827 workers employed for at least one year between 1950 and 1998 by one o f 14 large B C sawmills. There were 7,496 cohort members  21  who died or were lost to follow-up or left the province prior to A p r i l 1989. O f the remaining 21,301 workers, a total o f 19,972 were linked with health outcome data and therefore eligible for inclusion in this study. The study participants were followed from A p r i l 1989 to the study end date (December 1998), date o f death, date o f last observation, or the health outcome o f interest (work-related injury) which ever occurred earlier. [Appendix 4: The Sawmill Cohort] O f the study mills, six were located on Vancouver Island, five on the south coast o f B C mainland, and three i n the interior o f the province. A t each m i l l , data were abstracted from personnel records to construct two files. One with personal information including worker's name and date o f birth; and another with the job history including hire date, work department, and start and end dates for each new job held at the m i l l [Hertzman et al, 1997; Teschke, 1998].  1.11.4 BRITISH COLUMBIA LINKED H E A L T H DATABASE The British Columbia Linked Health Database ( B C L H D ) is a health data resource created and maintained by the University o f British Columbia Centre for Health Services and Policy Research [ C H S P R , 2004]. It contains datasets recording physician visits, hospital discharges, deaths, births, as well as extended care, drug usage, and workers' compensation claims [ C H S P R , 2004]. The data sets are all linked to a central registry file o f all persons in the province covered by the B C Medical Services Plan ( M S P ) . [See Appendix-3: British Columbia Linked Health Database Contents for more information]. Almost all eligible residents o f B C (over 4.1 million people) are enrolled with M S P [ B C Ministry o f Health, 2004]. Members o f the B C Sawmill Cohort Study were linked with hospitalization records and claims records using the B C L H D . A s part o f previous studies, 19, 972 members o f the B C Sawmill Cohort Study were linked with hospitalization records using the B C L H D by A p r i l 1989. They were linked to the  22  B C L H D by probabilistic linkage using names, birth dates and where available Social Insurance Numbers as identifiers [Hertzman et al., 1997]  1.11.5 H O S P I T A L D I S C H A R G E D A T A The hospital discharge dataset consists o f all separations (discharges, transfers, and deaths) for in-patients or day surgery patients admitted to acute care hospitals in British Columbia [ C H S P R , 2004]. A m o n g many other variables, admission and separation dates, and payment modes (indicating agency responsible for paying medical costs) are recorded along with the name o f hospital. Each record is described as elective, urgent or emergency. There are up to 16 I C D - 9 (International Classification o f Diseases) diagnosis codes available to describe the event. The first is considered the primary reason for hospitalization. The I C D - 9 nature o f injury codes and I C D - 9 cause o f injury codes were used in the study to identify and describe injury events.  The International Classification o f Diseases (ICD) is the classification system used to code and classify mortality data from death certificates. The International Classification o f Diseases, Clinical Modification ( I C D - 9 - C M ) was used to code and classify morbidity data from the inpatient and outpatient records, and other administrative databases included in the B C L H D during the study period. The I C D - 9 - C M is based on the W o r l d Health Organization's Ninth Revision, International Classification o f Diseases [ I C D - 9 - C M ] . I C D - 9 - C M was the official system o f assigning codes to diagnoses and procedures associated with hospital utilization i n the United States and Canada before ICD-10 became available. In this study, the terms I C D - 9 and I C D - 9 - C M are used synonymously.  23  1.11.6 WORKERS' COMPENSATION DATA The B C Linked Health Database has information on all claims compensated by the Workers' Compensation Board o f B C ( W C B ) from the year 1987 onwards [ C H S P R , 2004]. The detailed information on the injury related claims include injury date, I C D - 9 codes, source of injury, nature o f injury, and body parts involved.  1.11.7 CLAIM COSTS For an injury claim, comprehensive compensation cost data for up to 7 years after the event were collected directly from the W C B . The claim cost information was classified by level o f compensation benefits: health care only, short-term disability (time-loss), long-term disability (permanent disability), vocational rehabilitation and fatality.  1.11.8 HOSPITAL BILLING INFORMATION Standard Ward Rate for the daily charge for hospital stays was collected from the British Columbia provincial Ministry o f Health. It is used also for inter-provincial and workers' compensation billing purposes. This rate is calculated yearly and is also site-specific [ B C Ministry o f Health, 1989-1998].  1.11.9 ETHICS APPROVAL The study was approved by the behavioural research ethics board o f the University o f British Columbia.  24  F I G U R E 1.1: S C H E M A T I C D I A G R A M O F I N J U R Y P A T H W A Y  M i n o r Cost  N o Irnpairrnent  M i n o r Cost  N o Lasting Functional Limitation  N o n Fatal Injury  Work Disability  Major Cost  Impairment Functional Limitation  Non-Work Disability  Modest Cost  Adapted from D a v i d W e i l : Valuing the economic consequences o f work injury and illness: A comparison o f methods and findings. American Journal of Industrial Medicine 40:4: 418 - 437  25  FIGURE 1.2: IDENTIFICATION OF A WORK-RELATED INJURY  Identified by Place of Occurrence in hospital records  Not Filed for Compensation  Claims Rejected  Work-related Hospitalized Injury  Filed for Compensation  \  Identified by Responsibility of payment in hospital records  Identified through linkage with compensation records  26  1.12 R E F E R E N C E S A W C B C , 2006. Association o f Workers' Compensation Boards o f Canada. Workers' Compensation Board/Commission Financial and Statistical Data http://www.awcbc.org/english/board_data.asp Accessed January 02, 2006.  Azaroff L S , Levenstein C , Wegman D H . 2002. Occupational injury and illness surveillance: conceptual filters explain underreporting. A m J Public Health 92:1421-9.  Barroetavena M C . 2001. A n epidemiologic investigation o f injury mortality among sawmill workers. P h . D . Thesis. 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Can J Public Health 96:333-9.  34  CHAPTER2 AN EVALUATION OF HOSPITAL DISCHARGE RECORDS AS A T O O L FOR SERIOUS WORK-RELATED INJURY SURVEILLANCE  1  2.1 INTRODUCTION Workers' compensation claims data represents an important source o f information on work-related injuries. Compensation statistics are compiled using only officially reported and accepted claims. However, several recent studies in the U S A [Waller et al., 1989; Frumkin et al., 1995; Stanbury et al., 1995; Biddle et al., 1998; Rosenman et al., 2000] and Canada [Shannon and Lowe, 2002] have found that workers injured i n the workplace do not always report injuries or file a claim for workers' compensation. Work-related injuries may not be reported to compensation systems for numerous reasons, such as discouraging supervisors and coworkers, job insecurity, legal status, procedural complications, unawareness about the system, high odds o f having a claim rejected, injury not serious enough, and social stigma [ Herbert et al., 1999; Rosenman et al., 2000; Shannon and Lowe et al., 2002]. Additionally, workers' compensation does not accept all o f the claims filed [Stanbury et al., 1995; Herbert et al., 1999]. In addition to workers' compensation claims data, other sources o f information including emergency department reports, physician claims data, police reports, newspaper clippings, surveys, and workplace incident reports have been explored as a means to determine the number o f non-fatal work-related injuries [ M c C u r d y et al., 1995; Hayden et al., 1995; Murphy et a l , 1996; van Charante and Mulder, 1998, Morse et al., 2001; Tercero et al., 2004]. Hospital The chapter has been published under the same title in Occupational and Environmental Medicine 2006; 63(4): 290-6. This article is Reprinted with permission of BMJ Publishing Group Ltd 1  35  discharge records represent yet another readily available source o f data for the monitoring o f severe non-fatal injuries. Hospital discharge records have detailed information on the nature, cause and severity o f injuries in Canada, and the records are collected objectively outside o f the contentious arena o f attribution. Despite their potential to capture work-related injury, little research has been carried out on their validity and completeness [Sorock et al., 1993; Baker et al., 1999]. In Canada, a few studies have attempted to identify work-related events using hospital discharge records, but have focused on capturing a specific range o f events, such as those related to agricultural machineries or occupational asthma [Dimich-Ward et al., 2004; Locker et al., 2002, Liss et al., 2000]. According to our knowledge, studies in Canada have neither used hospital data for more general injury surveillance nor validated its use against other available indicators. Hospital discharge records have the potential to be a useful data resource for surveillance because o f the public health care system in Canada, and the  comprehensive  coverage o f hospitalizations at the population level. The challenge i n utilizing hospital discharge data for work-related injury research is differentiating work from non-work-related injuries. The International Classification o f Disease Revision 9 Clinical Modification (ICD-9) [ I C D - 9 - C M ] coding scheme includes external codes or " E " codes that indicate the source o f injury (for example, motor vehicle, machinery, fire, etc.) for injury related diagnosis. Some o f these E codes can be used to specify the work relatedness o f an injury. Additionally, starting in A p r i l 1989, hospitals in the Canadian province o f British Columbia ( B C ) began to code a fifth digit indicating whether or not the injury occurred at a workplace for certain E Codes. The hospital discharge  records  in B C also contain a  responsibility for payment schedule, which includes the option o f selecting the provincial workers' compensation agency - the Worker's Compensation Board o f B C ( W C B ) . The  36  availability o f two indicators also provide the opportunity o f estimating the hospitalized cases that would remain unascertained through an appropriate statistical method, such as the capturerecapture method [Morse et al., 2001]. The sawmill industry in British Columbia represents an important workplace setting to investigate the use o f hospital discharge records for work related injury surveillance because o f both its hazardous work environments and importance to the local economy. In the province o f British Columbia, about 2% o f the workforce was working in the logging and forestry industry during 1993-1998 [ B C Statistics, 2004]. Sawmills and other lumber mills are hazardous work environments due to the nature o f the work processes, the types o f equipment used, and materials handled [Demers and Teschke, 1998]. From 1993 to 1997, the average accepted, time-loss claim rate was 7 injuries per 100 full-time equivalent workers in B C sawmills compared to the overall provincial average o f 5.4 injuries [ W C B , 1999]. A large cohort study on sawmill workers i n B C , initially started in the 1980s to investigate the risk o f cancer associated with the use o f Chlorophenol fungicides [Hertzman et al., 1997], was expanded to investigate a wide variety o f occupational health issues in the forest industry [Teschke et al., 1998]. This study used two study populations: a) the full cohort, which included members who might not be working in sawmills at the time o f hospital admission (moved out o f the study sawmills at some point during the follow up period); and b) a sub-set o f the cohort members who were working in the study sawmills at the time o f hospital admission. This investigation captured and described work-related serious injuries using the indicators available in hospital discharge records from 1989 to 1998. It compared the agreement and capturing patterns o f the work related indicators (E codes and responsibility for payment), and investigated whether the agreement between the two indicators i n this surveillance system varied  37  by causes o f injuries or types o f populations. It also attempted to estimate the number o f hospitalized injuries that were undetected b y both sets o f indicators.  2.2 METHODS 2.2.1 THE SAWMILL COHORT The B C sawmill cohort originally includes 28,827 workers employed for at least one year between 1950 and 1998 by one o f 14 large B C sawmills. There were 7,496 cohort members who died or were lost to follow-up, or left the province prior to A p r i l 1989. Thus, for this study, the population base was the rest o f the cohort members (21,301). From the work history records, 6,512 cohort members were selected for the second set o f analysis, all o f who were working in sawmills on or after A p r i l 1989. The study populations were followed up from A p r i l 1989 for health outcomes to study end date (December 1998), date o f death, or date o f last observation, whichever occurred earlier. Hospital discharge records were extracted for an injury diagnosis between A p r i l  1989 and December 1998. Injuries among the cohort members  captured  hospitalization incidents that occurred while the cohort members were employed in study sawmills, in other sawmills, in another industry, or were out o f work.  2.2.2 BRITISH COLUMBIA LINKED H E A L T H DATABASE The British Columbia Linked Health Database ( B C L H D ) is a health data resource created and maintained b y the University o f British Columbia Centre for Health Services and Policy Research [ C H S P R , 2004]. It contains datasets recording physician visits, hospital discharges, deaths, and births, as well as extended care, drug usage, and workers' compensation claims from 1985 [ C H S P R , 2004]. The data sets are all linked to a central registry file o f all persons i n the province covered b y the B C Medical Services Plan ( M S P ) [Chamberlayne et al., 1998]. Almost  38  all eligible residents o f B C (over 4.1 million people) are enrolled with M S P [ B C Ministry o f Health, 2004]. The M S P processes claims for insured services submitted by physicians, supplementary health care practitioners, hospitals, laboratory services and diagnostic procedures [BC Ministry o f Health, 2004]. The hospital discharge dataset used i n this study came from the B C L H D . A s part o f previous studies, 19, 972 members o f the B C Sawmill Cohort Study were linked with hospitalization records using the B C L H D by A p r i l 1989. They were linked to the B C L H D by probabilistic linkage using names, birth dates, and where available, Social Insurance Numbers as identifiers [Hertzman et al., 1997]. A m o n g the 6,512 cohort members actively employed on or after A p r i l  1, 1989, a total o f 5,876 members were linked with their  hospitalization records.  2.2.3 H O S P I T A L D I S C H A R G E D A T A The  hospital discharge dataset consists o f all separations (discharges, transfers, and  deaths) for inpatients or day surgery patients admitted to acute care hospitals i n British Columbia [ C H S P R , 2005]. A n injury related hospital admission is described by cause o f injury (E codes) and nature o f injury (ICD-9 N codes). External causes o f Injury and Poisoning (E800-E998) codes are applicable to describe the accident, circumstance, event, or specific agent, which caused the injury or other adverse effect [ICD-9]. These E codes are used in addition to the nature o f injury or poisoning codes (ICD-9 N codes), which range between 800 and 999 [ICD-9]. U p to 16 diagnoses are available using the I C D - 9 codes to describe the nature and cause o f a hospital admission. The principal diagnosis for the patient's stay in a hospital was used to designate the nature o f an injury for this analysis. This diagnosis code was accompanied by E  39  codes present in one or more o f the 15 other fields; the first E code i n order o f presence was used to identify the cause o f an injury. O f the 40,806 hospital discharge records extracted among the full study cohort, there were 3,317 cases (8.13%) where the principal diagnoses were injury (ICD-9 N codes ranged between 800 and 999), and o f these, 3,305 (99.6%) were E Coded (Figure 2.1). From the E Coded segment o f the total hospitalization records (3,305), a subset o f hospitalization records with cause o f injury codes that have a minimal probability o f being occupational in nature were excluded from our analysis (Figure 2.1). In this study, work-related injuries were identified by two indicators. The first indicator relied solely on the I C D - 9 E-codes. Table 2.1 lists the indicators o f work-relatedness available in the digits o f the E codes [ICD-9]. The second indicator used to describe work-related injuries in the hospital discharge records was the field indicating the agency responsible for payment o f the patient's hospitalisation. The second indicator was considered as a surrogate o f workers' compensation claim filed for that injury, as at that point, no further information was available to know whether an injury related claim was essentially filed or compensated subsequently.  2.2.4 A N A L Y S I S Each injury was classified as work related using E-codes and then again using payment schedules. Next, the relationship o f work-relatedness with the demographic and hospital characteristics was explored for both study populations. Demographic characteristics included age, sex, and race; and hospitalization characteristics included type o f admission (for example, elective, urgent, emergency), level o f care (for example, acute care, day care surgery), and length of stay. The concordance o f the two work-relatedness identifiers (E code versus payment  40  schedule) was examined by cause o f injury. The Kappa statistic was calculated to measure the agreement between the two work-related indicators [Maclure and Willett, 1997]. Capture-recapture methods were used to estimate the number o f injuries that were unreported in both the study populations. The capture-recapture method estimates the extent o f incomplete ascertainment using population-based data from two independent and overlapping sources. This methodology originated i n wildlife biology and demography, and has been tailored into epidemiology to determine population parameter estimates derived from two or more imperfect sources [Morse et al., 2001]. This method was described by Hook and Regal [1995]. It attempted to estimate the number o f hospitalized work related injuries that were undetected by both sets o f indicators. The study was approved by the behavioural research ethics board o f the University o f British Columbia.  2.3 R E S U L T S O f the 1,885 hospital records selected for the first set o f analysis, 547 (29%) were identified as work-related by either the E codes or the payment fields. For the active sawmill workers, 173 (47%) out o f the 370 hospitalizations were identified as work related (Table 2.2). Table 2.2 shows important demographic and hospital characteristics o f the work related and total injury related hospitalization records for both study populations. The active sawmill workers were significantly younger and the proportion o f Asians among this group was higher than that in the full study cohort. In the full study population, there were no significant differences in the distribution o f hospitalizations by sex, race, admission category, level o f care, or length o f stay for any hospitalization compared to work related hospitalizations. There were no major differences in  41  the distribution o f hospitalizations by sex, age, admission category, or level o f care for any hospitalization compared to work related hospitalizations in active sawmill workers. A m o n g the cohort members who were not working i n the study sawmills any longer, almost half o f all injury hospitalizations among people aged 30-34 years, and one third among aged 25-29 and 35-59 years were found to be work-related (Figure 2.2). The work-related injury hospitalizations were notably greater for the active sawmill workers who were <20 years or 4564 years compared to other cohort members. More than half o f all hospitalizations among workers <20 years, 45-54 years, and 60-64 years were work-related among the active sawmill workers (Figure 2.2). Table 2.3 compares the two sources o f work-related injury identification by the cause o f injury categories for the full cohort. The payment field identified 83.9% (n=459) o f the total work-related cases (n=547), and E codes identified 84.4% (n=462) o f the work-related cases (Figure 2.3). The indicators provided the same assessment i n 68.3% (374) o f the total cases. For some causes o f injury, such as struck by a falling  object; other & unspecified; and railway,  water, air & powered vehicles, the payment field picked up more work-related cases, and for others, such as struck against, machinery related, and cutting & piercing, the E Code field was able to identify more work related cases. The two sources had relatively poor concordance for injuries, such as machinery-related,  struck by falling  object, overexertion,  and caught in or  between, as measured by kappa statistic. There was better agreement for injuries, such as, struck against; drowning, suffocation, foreign body in eye, other foreign body; fire, flame, natural & environmental; and explosions, firearms, hot substance, electric current & radiation. For the full study population, there were 324 records for which E Codes did not have information on workrelatedness; thus the agreement between the two sources i n determining work-relatedness o f  42  injuries was calculated for the rest o f the 1,561 records. The agreement between them was found to be good (kappa= 0.75; p O . O l ) . Table 2.4 compares the two indicators o f work related injury identification by the cause of injury categories for the active sawmill workers. The payment field identified 86.7% (150) o f the total work-related cases (n=370), and E codes identified 91.3% (158) o f the cases as work related injuries (Figure 2.3). Both o f them agreed on 78% (135) o f the total cases. B y either o f the two sources, almost half (47%) o f all hospital visits for injuries were identified as work related. Both fields were able to capture proportionately more work related events among actively employed people. In these active sawmill workers, for all causes o f injury, except other & unspecified, E Codes were able to identify equal or more numbers o f work related cases. There was relatively poor concordance for injuries, such as machinery related; struck by falling object; caught in or between; and railway, water, air & powered vehicle. For the active sawmill workers, there were 44 records for which E Codes information was not available; thus the agreement between the two sources i n respect to identifying work-relatedness was calculated for the rest o f the 326 records. The agreement was also good (kappa= 0.77; p<0.01). To obtain an unbiased estimate for the number o f unascertained cases for the full cohort population by these two sources, a capture-recapture method was applied. The results o f the capture-recapture method suggested that there were 16 (1%) more work-related cases that went undetected by either o f these two indicators. Therefore, adding these 16 to our already identified cases resulted i n an estimated 563 hospitalizations for work-related injuries i n our full study population. Application o f the capture-recapture method also suggested that there were 2 (0.6%) more work-related cases that were undetected by the two sources, increasing the total workrelated injury admissions to 175 among those actively employed in the sawmill industry.  43  2.4 D I S C U S S I O N Both E codes and payment schedules available in hospital discharge records were useful in capturing work related severe injury incidents in the active sawmill workers and full cohort populations. Interestingly, the E Codes in hospital records picked more work related injury cases than the responsibility o f payment field for the active sawmill workers. However, identification by payment field picked up equal or more cases for several injury categories in the full study group. The E codes and payment fields have been examined in other studies as a tool for injury surveillance. Sorock and colleagues [1993] found 11% o f hospital discharge records with external cause o f injury codes. Smith and colleagues [Smith et al., 1990] found 13.9% hospital discharge records with at least one injury-related diagnosis or health service code, and 99.3% o f them were E Coded. These findings are consistent with what we have found i n this study. Sniezek and colleagues [1999] suggested that E Coded hospital discharge data systems were potentially one o f the most effective and feasible means available to collect data needed for injury surveillance. Smith and colleagues [1990] recommended that with uniform guidelines and better training o f coders, the E coding system could provide a valuable, cost-effective method o f identifying non-fatal injuries. Baker and colleagues [1999] used California hospital discharge database to identify hospitalized ocular injury, and used workers' compensation as principal payer to identify work-relatedness. Sorock and colleagues [1993] suggested that the payment field i n hospital data might be a good to excellent indicator o f work-relatedness o f hospitalized injuries. The most frequent causes o f hospitalizations in our study populations were falls, motor, road vehicle, overexertion, machinery related, struck against, and cutting & piercing. The most  44  frequent causes o f work related hospitalizations were falls,  machinery  related,  overexertion,  struck against, cutting & piercing, and struck by falling objects. A m o n g the workforce employed in sawmills, the two indicators identified almost all cases o f machinery related, struck by falling object and caught in or between injuries as work-related. From 1993 to 1997, the Workers' Compensation Board o f B C accepted a total o f 11,685 time-loss claims from sawmills, with most being for overexertion, struck by, caught in, and falls [ W C B , 1999]. There are two main reasons why injuries captured b y hospital discharge records and workers compensation authority might be different i n terms o f severity and nature. First, the W C B has its own way o f coding injury information. Second, there are injuries, which might result i n time-loss without requiring a hospital visit. People  with work-related  injuries  were  younger  compared  to  those with  any  hospitalization i n the full study population. Younger people are more likely to be active sawmill workers. A n international literature review o f 63 nonfatal studies by Salminen [2004] found that younger workers had a higher injury rate than older workers. The injury rate for young male workers (the number o f short-term disability claims per 100 person-years o f employment) was higher than the overall provincial average during 1976 to 1997 also i n the province o f British Columbia [ W C B , 2004]. This study captured work-related injury among workers who were less than 20 years o f age. There were 17 workers who were below 18 years during their injury admission in the full study population; two o f them had work related injury. In our study, the work-related indicators failed to identify any work related injuries among the individuals o f 65 years or older. This adds validity to our case definition o f a work related hospitalization i n this study as the province o f B C has a mandatory retirement age o f 65 years.  45  The findings o f this study should be interpreted carefully due to the following limitations. It excluded from analysis certain injuries that had a small likelihood o f being work-related. For (.  example, we could have missed some work-related injuries coded as medical adverse events, violence, and medical misadventure.  The records with the workers' compensation i n payment  field were used i n this study as a proxy for claims actually compensated by the workers' compensation agency. It was not possible to verify this as we did not have the real compensation claims data for the study populations. Given the prevailing external cause o f injury coding patterns, work-related injury identification would more be feasible for manufacturing industries. For capture-recapture analysis, source dependency should be avoided [Morse et al., 2001]. Provided that different coders coded the ICD-9 codes and payment field on the same dataset, some independency was ensured, though there were chances o f cross-contamination. A l s o , about 10% o f the active sawmill workers were not linked to the B C L H D , and the linkage rate was found lower for young people, female, and South Asians. The principal diagnosis for the patient's stay in a hospital was used to designate the nature o f an injury for this  analysis. Whereas,  this might  create some  measures o f  misclassification for cases which had more than one equally significant diagnosis, we decided to depend on the judgment o f the attending physician who determined which code should be the principal diagnosis. For acute and severe injury requiring hospitalisation, the first diagnosis should ideally represent the more immediate and real nature o f an injury. Our study depended heavily on the accuracy o f the codes available in hospital data. Studies outside Canada [Sorock et al., 1993; Baker et al., 1999, Smith et al., 1990] and inside Canada [Dimich-Ward et al., 2004; Locker et al., 2002; Liss et al., 2000] used hospital discharge datasets. The reliability and validity o f hospital records were examined by some  studies  46  [Vestberg et al., 1997; Rawson and M a l c o l m , 1995; Kashner, 1998; Beghi et al., 2001]. A l s o , a review by V i r n i g and M c B e a n [2001] recommended  the use o f electronically available  administrative data for surveillance purposes. However, since some o f the hospital discharge codes, especially the fifth digit E codes were introduced only i n 1989 in British Columbia, it might somewhat under-report the work related cases for the first few years. Provided the responsibility o f payment field worked well as a surrogate for workers' compensation claims, the hospital discharge records support some degree o f under-reporting o f work-related injuries by the official workers' compensation agency statistics. There is no gold standard for work-related injury surveillance tools as the workers' compensation agency does not capture, accept, or report on all injuries. While there are complaints o f underreporting against the workers' compensation authority, it should be sensitive enough to capture information on injuries severe enough to reach a hospital. Matching o f a work related hospital record with actual W C B claim can help validate hospital records as a potential surveillance tool. Hospital discharge data are collected for administrative reasons, and thus are readily available. They are especially suitable for retrospective studies covering longer periods o f observation. Depending on the coding reliability and validity o f specific databases, hospital data represent an alternative source o f information for compensation related statistics for serious work related injuries. K n o w i n g the causes and nature o f injuries that remain unreported w i l l be helpful to employers, compensation officials, and other stakeholders to identify vulnerable groups, and subsequently target preventive measures within an industry. Accurate reporting o f work-related injuries could impact regulatory processes and prevention strategies b y estimating the actual size o f the problem faced by both employers and the workforce. I f injuries among employed persons  47  are not documented as work-related, policy and prevention decisions may not be based on accurate or complete evidence; employees may not receive needed  compensation and  rehabilitation services, and the cost o f some work-related injuries may end up being paid by other parts o f the social safety net (for example, the publicly funded health care system).  48  T A B L E 2.1: E-CODES, INJURY CATEGORIES, AND MEANS OF IDENTIFYING WORK-RELATEDNESS* Category Description  E-code  Indicator of Work-Relatedness  Railway Water transport  E800-E807 E930-E938  4 digit: 0 = railway employee 4 digit: 2 = crew, 6 = dockers & stevedores 4 digit: 2 = crew, 8 = ground crew Primarily occupational by definition  [ICD-9] th th  th  E840-E845 Air & space transport E846 Powered vehicles used solely within industrial & commercial buildings E810-E829 Motor vehicle traffic, non-traffic & other road vehicle Vehicle accidents not elsewhere classifiable E847-E848 E860-E869 Other poisonings  No work-related E Codes indicating workrelatedness (only payment field used for these records) 5 digit, available April 1989 or later th  1. Farm Buildings, Land under cultivation Excludes: farm house and home premises of farm 2. Mine and quarry Mine, quarry, gravel pit, sand pit, tunnel under construction 3. Industrial place and premises Building under construction, industrial yard, loading platform (factory) (store), dockyard, dry dock, industrial plant, factory, railway yard, factory -building, premises, shop - place of work, warehouse, garage - place of work, workhouse E880-E888 Falls Fire & flame E890-E899 Natural & environmental (e.g. cold, heat, E900-E909 pressure) Drowning & suffocation E910-913 Foreign body in eye E914 Foreign body in other orifice E915 Struck by falling object E916 Struck against E917 Caught in or between E918 Machinery-related E919 Cutting & piercing E920 Explosions, firearms, explosive, hot substance, E921-926 corrosive, caustic, steam, electric current & radiation Overexertion E927 E928 Other & unspecified (noise & vibration)  Responsibility o f payment field was available for all categories  49  T A B L E 2.2: DEMOGRAPHIC AND HOSPITAL CHARACTERISTICS OF STUDY POPULATIONS Full Study Population (n= 19,972)  Active Sawmill Workers (n=5,876)  Charactenstie-^^^  N Sex  Male Age (Years) Mean (95% CI) Median Race White South Asian East Asian Length of Stay (Median) Admission Category Elective Urgent Emergency Level of Care Day care Surgery Fatal Cases  Total hospitalizations  Work-related hospitalizations* (%)  Total hospitalizations  Work-related hospitalizations*  (%) 1,885  547  (%) 370  (%) 173  1,868 (99%)  541 (99%)  363 (98%)  170 (98%)  50 [50-51] 47  43 [42-44] 43  41 [40-421 40  42 [41-44] 41  1,795 (95.2%) 82 (4.4%) 8 (0.4%)  520 (95.1%) 24 (4.4%) 3 (0.5%)  330 (89.2%) 37 (10%) 3 (0.8%)  156(90.2%) 15 (8.7%) 2(1.2%)  3 days  3 days  2 days  3 days  290(15%) 949 (50%) 646 (34.5%)  89 (16%) 279 (51%) 179 (33%)  72 (20%) 181(49%) 117(32%)  29 (17%) 84 (49%) 60 (35%)  346(18%) 46  115 (21%) 2  82 (22%) 3  33 (19%) 0  * Work-related hospitalizations were identified by either the E codes or the payment schedule.  50  T A B L E 2.3: IDENTIFICATION OF WORK-RELATED INJURY HOSPITALIZATION AMONG T H E FULL STUDY POPULATION BY CAUSE OF INJURY Injury Category  Falls Motor & road vehicle Overexertion Machinery related Struck against Cutting & piercing Drowning, suffocation, foreign body in eye, other foreign body Struck by falling object Fire, flame, natural & environmental Caught in or between Explosions, firearms, hot substance, electric current, radiation Railway, water, air & Powered vehicle Other poisonings Other & unspecified Total  Kappa Statistic (p value)  Either payment or E Codes indicate Workrelatedness (%) 139 (21) 15(5) 61 (32) 123 (80) 46 (34) 41 (38) 4(9)  Payment indicates Workrelatedness  E Codes indicate workrelatedness  (%)  (%)  663 324 188 154 137 108 45  117(18) 15(5) 47 (25) 102 (66) 40 (29) 29 (27) 4(9)  116(18) NA 46 (24) 114(74) 44 (32) 39 (36) 4(9)  0.77 NA 0.59 0.54 0.86 0.70 1.00  44 42  27 (61) 13 (31)  23 (52) 16(38)  0.45 (O.01) 0.84 (<0.01)  31 (70) 16(38)  39 34  27 (69) 18(53)  28 (72) 19(56)  0.57(<0.01) 0.94 (O.01)  31 (79) 19 (56)  27  8(30)  6(22)  0.81 (O.01)  8(30)  17 63 1,885  4(24) 8(13) 459 (24)  5(29) 2(3) 462 (25)  0.85 (O.01) 0.37 (O.01) 0.75 (O.01)  5(29) 8(13) 547 (29)  Frequency of hospital admissions  (O.01) (O.01) (O.01) (O.01) (O.01) (O.01)  51  T A B L E 2.4: I D E N T I F I C A T I O N O F W O R K - R E L A T E D I N J U R Y H O S P I T A L I Z A T I O N A M O N G A C T I V E S A W M I L L W O R K E R S B Y C A U S E O F INJURY \  Injury Category  Falls Struck against Machinery related Motor & road vehicle Overexertion Cutting & piercing Other & unspecified Struck by falling object Caught in or between Fir, flame, natural, environmental Railway, water, air, powered vehicle Drowning, suffocation, foreign body in eye, other foreign body Explosions, firearms, hot substance, electric current, radiation Other poisonings Total  Payment indicates Workrelatedness (%)  Frequency of hospital admissions  E Codes indicate workrelatedness (%)  Kappa Statistic (P value)  0.84 ( O . O l ) 0.85 ( 0 . 0 1 ) 0.30 ( 0 . 0 1 ) NA 0.78 ( 0 . 0 1 ) 0.82 ( 0 . 0 1 ) 0.49 (0.02) 0.15 (0.57)  Either payment or E Codes indicate Workrelatedness (%)  30 (36) 24 (45) 49 (94) 1(2) 16(40) 9(36) 5(29) 13 (93)  84 53 52 44 40 25 17 14  25 (30) 21 (40) 44 (85) 1(2) 13 (33) 7(28) 5(29) 11 (79)  29 (35) 23 (43) 45 (87) NA 15 (38) 9(36) 2(12) 11 (79)  11 10  8(73) 6(60)  8(73) 7(70)  0.54 (0.07) 0.78 (0.01)  9(82) 7(70)  6  2(33)  1(17)  0.57 (0.12)  2(33)  6  3(50)  3(50)  1.00 (0.01)  3(50)  6  3(50)  4(67)  0.67 (0.08)  4(67)  2 370  1(50) 150(41)  1(50) 158 (43)  1.00 (0.16) 0.77 ( 0 . 0 1 )  1(50) 173 (47)  52  FIGURE 2.1: STUDY POPULATIONS FOR ANALYSIS OF W O R K - R E L A T E D HOSPITALISATIONS  40,806 hospitalisation records  1  3,305 hospitalisation records had principal diagnosis injury and had E codes 1,420 records excluded for being primary non-occupational in nature Analysis o f 1,885 hospitalisation records  1  1,515 records excluded, as people were not working in sawmills during injury admission  Sub-analysis o f 370 hospitalisation records  53  FIGURE 2.2: AGE AND WORK-RELATED INJURY*  D  ?0  Won a c t i v e s a w m i l l w o r k e r s  1 A c t i v e sawmil w o r k e r s  60  r  so  £  40  3  30  *  20 10  <20  20-24  25-29  30-34  35-59 Age  40-14  45-19  50-54  55-59  60-64  >65  group (year*)  * Other sawmill workers are cohort members who were not working in study sawmills during injury  54  FIGURE 2.3: AGREEMENT BETWEEN TWO INDICATORS OF T H E HOSPITAL DISCHARGE RECORDS TO IDENTIFY WORK-RELATED CASES  F u l l study population (total=547)  Active sawmill workers (total=173)  2.5 REFERENCES Baker R S , W i l s o n R M , Flowers C W Jr, Lee D A , Wheeler N C . 1999. 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U S Department o f Health and Human Services. Hyattsville, M D .  Kashner T M . 1998. Agreement between administrative files and written medical records: a case o f the Department o f Veterans Affairs. M e d Care 36:1324-36.  Liss G M , Tarlo S M , Macfarlane Y , Yeung K S . 2000. Hospitalization among workers compensated for occupational asthma. A m J Respir Crit Care M e d 162:112-8.  Locker A R , Pickett W , Hartling L , Dorland J L . 2002. Agricultural machinery injuries in Ontario, 1985-1996: a comparison o f males and females. J Agric Saf Health 8:215-23.  57  Maclure M , Willett W C . 1987. Misinterpretation and misuse o f the kappa statistic. A m J Epidemiol 126:161-9.  M c C u r d y S A , Schenker M B , Samuels SJ. 1991. Reporting o f occupational injury and illness in the semiconductor manufacturing industry. A m J Public Health 81:85-9.  Morse T, D i l l o n C , Warren N , H a l l C , Hovey D . 2001. 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A m J Ind M e d 42:467-73.  Smith S M , C o l w e l l L S Jr, Sniezek J E . 1985. A n evaluation o f external cause-of-injury codes using hospital records from the Indian Health Service, 1985. A m J Public Health 80:279-81.  Sniezek J E , Finklea JF, Graitcer P L . 1989. Injury coding and hospital discharge data. J A M A . 262:2270-2.  58  Sorock G S , Smith E , H a l l N . 1993. A n evaluation o f N e w Jersey's hospital discharge database for surveillance o f severe occupational injuries. A m J Ind M e d 23:427-37.  Stanbury M , Joyce P, K i p e n H . 1995. Silicosis and workers' compensation i n N e w Jersey. J Occup Environ M e d 37:1342-1347.  Tercero F , Andersson R. 2004. Measuring transport injuries in a developing country: an application o f the capture-recapture method. A c c i d A n a l Prev 36:13-20.  Teschke K , Ostry A , Hertzman C , Demers P A , Barroetavena M C , Davies H W , Dimich-Ward H , Heacock H , M a r i o n S A . 1998. Opportunities for a broader understanding o f work and health: multiple uses o f an occupational cohort database. Can J Public Health 89:132-6.  van Charante A W , Mulder P G . 1998. Reporting o f industrial accidents i n The Netherlands. A m J Epidemiol 148:182-90.  Vestberg K , Thulstrup A M , Sorensen H T , Ottesen P, Sabroe S, Vilstrup H . 1997. Data quality o f administratively collected hospital discharge data for liver cirrhosis epidemiology. J M e d Syst 21:11-20 V i r n i g B A , M c B e a n M . 2001. Administrative data for public health surveillance and planning. A n n u Rev Public Health 22:213-30. Waller J A , Payne S R , Skelly J M . 1989. Injuries to carpenters. J Occup M e d 31:687-692.  W C B , 1999. Focus Report on Preventing Injuries to Workers. Forest products manufacturing. Injury rate in sawmills, p 23-34  W C B , 2004. Workers' Compensation Board o f British Columbia, Y o u n g Worker Fact Sheet. http://www.worksafebc.com/news/campaigns/young_workers/previous_years/assets/pdf/yw991. pdf. Accessed October 05, 2004  59  CHAPTER 3 HOW MANY WORK-RELATED INJURIES REQUIRING HOSPITALIZATION IN BRITISH COLUMBIA ARE CLAIMED FOR WORKERS' COMPENSATION?  2  3.1 INTRODUCTION The collection, analysis, and dissemination o f work-related injury data can provide useful and often essential information for the development o f injury prevention strategies. For example, injury surveillance mechanisms can be used to interpret and understand the incidence and patterns o f injury, as well as facilitate the design and evaluation o f intervention programs at an industrial and government level. However, the validity o f many work-related injury surveillance tools has not often been evaluated in terms o f capturing pattern and information accuracy. Workplace compensation claims datasets represent an important source o f information on work-related injuries. However, a key concern about the compensation statistics is that they are based on reported and accepted claims only. Several recent studies i n the U S A [Waller et al., 1989; Frumkin et al., 1995; Stanbury et al., 1995; Biddle et al., 1998; Rosenman et al., 2000] and Canada [Shannon and Lowe, 2002] have identified underreporting o f work-related injuries to the compensation systems. Work-related injuries are not always reported to workers' compensation systems for several reasons, such as discouraging supervisors and coworkers, legal status, job insecurity, high odds o f having a claim rejected, procedural complications, unawareness about  The chapter has been published under the same title in American Journal of Industrial Medicine 2006; 49(6):443451. This article is Reprinted with permission of Wiley-Liss, Inc. a subsidiary of John Wiley & Sons, Inc 2  60  the system, injury not considered serious enough, and social stigma [Herbert et al., 1999; Rosenman et al., 2000; Azaroff et al., 2002; Shannon and Lowe, 2002]. A s well, the workers' compensation system does not compensate every claim that is filed [Stanbury et al., 1995; Herbert et a l , 1999]. In addition to workers' compensation claims data, some other surveillance tools for nonfatal work-related injuries have been explored [McCurdy et al., 1991; Hayden et al., 1995; Murphy et al., 1996; van Charante and Mulder, 1998; Morse et al., 2001; Tercero and Andersson, 2004]. Hospital discharge data are a potential source o f information on more severe injuries.  Work-related injuries  reported  i n a hospital should overcome  barriers  within  organizations that might prevent reporting o f such events [Azaroff et al., 2002]. External cause o f injury codes and source o f payment information are available i n hospital discharge records to potentially identify work-relatedness o f an injury in British Columbia (BC), Canada [Alamgir et al., 2006]. Since A p r i l 1989, the hospitals in B C started coding an additional digit the International Classifications o f Disease diagnosis schedule to indicate whether or not the injury was work-related, which enhanced its utility as a work-related injury surveillance system [Alamgir et al., 2006]. Hospital discharge records can be used to efficiently evaluate the pattern and extent o f reporting by other surveillance systems, such as workers' compensation, because this data is routinely collected for administrative reasons and is readily available in electronic databases. The workers' compensation system covers about 90% o f workforce in the province o f B C [ W C B , 1998; British Columbia Statistics, 2005]. Employers are required by law to register their business/firm with the compensation authority and pay premiums. Coverage is usually higher for large, high-risk, and unionized industries and lower for small employers  (>3  61  employees), self-employed individuals, and federal worksites. If a worker is injured while on the job during the course of employment, the compensation authority usually pays for the worker's medical and wage-loss costs. This study attempted to determine work-related injury capturing patterns of the workers' compensation system by investigating the agreement of compensation records and hospital discharge records for a cohort of sawmill industry workers in BC. The injuries admitted to hospitals through urgent and emergency departments are usually acute and severe in nature. Emergency admission is considered to be life/limb threatening and urgent is also serious admission but not life/limb threatening in BC hospitals. It is hypothesized that the compensation system should be sensitive enough to capture most of these work-related injuries. In addition to testing the aforementioned hypothesis, this study examined the extent to which workers' compensation capturing patterns varied by cause, severity of injuries, and demographic characteristics of workers. The sawmill industry in BC represents an important workplace setting to investigate the use of hospital discharge records and compensation records for work-related injury surveillance both because of its hazardous work environments and importance to the local economy. A large cohort study on sawmill workers in BC was started in the 1980s to investigate the risk of cancer associated with the use of chlorophenol fungicides and later expanded to examine other health issues in the industry [Hertzman et al., 1997; Teschke et al., 1998]. This study used two study populations: (a) the full study population, which included members who might not be working in sawmills at the time of hospital admission (moved out of the study sawmills at some point during the follow-up period) and (b) active sawmill workers—a sub-set of the cohort members who were working in the study sawmills at the time of hospital admission. This examination of both  62  populations w i l l be used to determine whether the agreement between the two surveillance systems (i.e., workers' compensation files and hospital discharge records) differed for the active sawmill workers versus the full study population.  3.2 METHODS AND DATA SOURCES 3.2.1 THE SAWMILL COHORT The B C sawmill full cohort includes 21,301 workers employed for at least 1 year by one of 14 large B C sawmills between 1950 and 1998, who were being followed on or after A p r i l o f 1989. Demographic records on the cohort members include information on sex, race, and birth date; and work history records includes information on m i l l , department, start and end o f employment, start and end dates o f all unique jobs held at the m i l l , and job descriptions. The study population was followed from A p r i l 1989 for health outcomes to the study end date (December 1998), date o f death, or date o f last observation, which ever occurred earlier. Hospitalizations from injuries among the full study population (21,301) that occurred while the cohort members were employed in study sawmills, in other sawmills, in another industry, or were out o f work were captured. From the work history records, 6,512 cohort members were selected, all o f them were working i n study sawmills on or after A p r i l 1989. Work-related injuries were identified among this group o f people who were known to be working i n sawmills during the time o f injury-related hospital admissions. Hospital discharge records and workers' compensation records from A p r i l 1989 to December 1998 were extracted for both study populations [Alamgir et al., 2006].  63  3.2.2 BRITISH COLUMBIA LINKED H E A L T H DATABASE The British Columbia Linked Health Database ( B C L H D ) is a health data resource for research purposes created and maintained by the University o f British Columbia's Centre for Health Services and Policy Research. It contains datasets recording physician visits, hospital discharges, deaths, births, as well as extended care, drug usage, and workers' compensation claims since 1985 [ C H S P R , 2004-A]. Use o f the data for research purposes is governed by an access policy to protect privacy [ C H S P R , 2004-A]. The datasets are linked to a central registry file o f all persons  in the province covered by the B C Medical Services Plan ( M S P )  [Chamberlayne et al., 1998]. Almost all eligible residents o f B C (over 4.1 million people) are enrolled with M S P [ B C Ministry o f Health, 2004]. The M S P claims cover insured services submitted by physicians, hospitals, supplementary health care practitioners, and laboratory and diagnostic procedures. A s part o f previous cohort studies, 19,972 members o f the B C Sawmill Cohort Study were linked with their health records using the B C L H D as o f A p r i l 1989. A m o n g the 6,512 cohort members actively employed on or after A p r i l 1, 1989, a total o f 5, 876 members were linked.  3.2.3 HOSPITAL SEPARATIONS DATA Work-related injuries using hospital discharge data among this cohort o f sawmill workers were captured as part o f a prior investigation [Alamgir et al., 2006]. Work-related injury was identified using two indicator variables available. The International Classification o f Disease Revision 9 Clinical Modification (ICD-9) scheme includes external codes ( " E " codes) that indicate the cause o f an injury (e.g., motor vehicle, machinery, fire, etc.) [ I C D - 9 - C M ] . Starting in A p r i l 1989, hospitals in the Canadian province o f B C began to code a fifth digit indicating  64  whether or not the injury was work-related for certain E Codes (e.g., a fifth digit o f 2 indicate mine and quarry as the workplace for an injury). Other provinces in Canada have also been using these codes [CIHI, 1999]. The hospital discharge records also contain a second indicator variable that can be used to capture work-related events. Each injury record has a responsibility for payment schedule, which includes the option o f selecting the provincial compensation agency, which is the Worker's Compensation Board ( W C B ) i n B C . The methods are described by Alamgir et al. [2006]. From prior investigation, a total o f 1,885 hospitalization records were extracted for injury diagnosis between A p r i l 1989 and December 1998 for the full study population. B y using one or the other work-related indicators 547 hospitalizations (29%) were considered work-related. During the same period, there were 370 admission records for active sawmill workers. B y either of the two sources, 173 (47%) records were identified as work-related among this group. This analysis excluded work-related hospital admissions which were coded as elective admissions (i.e., only urgent and emergent cases were kept) for both sets o f study populations. The principal diagnosis for the patient's stay in a hospital was used to designate the nature o f an injury. Each hospitalization record was categorized into meaningful broad injury categories (Table 3.1).  3.2. 4 WORKERS' COMPENSATION DATA The B C L H D has information on all claims reported and compensated by the W C B o f B C from the year 1987 onwards [ C H S P R , 2004-B]. The claims are classified in terms o f level o f compensation awarded: health care only, short-term disability, long-term disability or fatality. There were 28,199 claims identified for the sawmill cohort between 1989 and 1998. Injury dates  65  were available for each claim. Claims with health care only outcomes did not have detailed injury information. There was detailed information on the injury for the rest o f the 8,103 claim records. This detailed information included ICD-9 codes, source o f injury, nature o f injury, and body parts involved. The ICD-9 codes o f the W C B records were used to identify claims and categorize each record into the broad groups o f injury (as described i n Table 3.1).  3.2.5 LINKING AND MATCHING COMPENSATION CLAIMS DATA AND HOSPITAL DISCHARGE DATA For linking the hospital and claim records, injury date, hospital admission and separation dates, and diagnoses codes i n both datasets were reviewed and qualitative assessment rules were applied. The date o f injury recorded i n the claim record for an injured individual and the dates o f admission and separation i n the hospital record for the same individual was used to link the two datasets. A l l linked records for which the date o f injury on the compensation claim for an individual was within the range o f 1 month prior to hospital admission date to 1 month after the hospital separation date were retained. A total o f 399 hospital records were linked to claim records following this strategy. After linking the two datasets, the following decision criteria were used to consider a claim i n the W C B data file as a proper match for an injury record i n the hospital data file. Meeting any o f these criteria qualified a record to be a proper match:  *  When the injury date reported for a claim was within 1 day o f admission date recorded i n  hospital discharge records. *  When the injury diagnosis o f both datasets fell under same injury category (as described  in Table 3.1).  66  *  For the records that did not exactly match by injury diagnosis category between the two  datasets, the principal I C D - 9 diagnosis codes o f both files were checked further to resolve minor disagreements. For example, an ICD-9 code o f 9223 (contusion o f back) i n a hospital record and a code o f 7245 (backache unspecified) i n a compensation claim were considered to be the same injury event. *  In addition to the principal diagnosis, the second diagnosis field o f the hospital records  described another important pre-admission condition o f the patient, which usually had a significant influence on the patient's length o f stay. For records unmatched by the first three rules, these secondary diagnosis codes o f hospital records were checked against compensation records to find additional matches. Out o f the 399 linked records, 391 hospital records were matched as the same event using these decision criteria; 315 records (81%) were matched by decision criterion o f 1 day, 23 records (6%) were matched by injury category, and an additional 53 records (13%) claims were matched b y the other two criteria.  3.2.6 ANALYSIS PLANS Each injury record in the hospital discharge records was first identified as work-related or not using the two available indicators, and then was checked as either claimed or not claimed for workers' compensation. The relationship o f claim status with demographic characteristics including age, gender, and race o f workers, and hospital characteristics including type o f admission, e.g., urgent, emergency; level o f care, e.g., day care surgery; and length o f stay was explored. Chi-square test was performed for statistical significance o f categorical variables and a two sample t-tests were performed for comparing means o f continuous variables. The agreement  67  between the hospital and compensation data was also examined for different causes of injury. A Kappa statistic was used to measure the agreement between the two data sources [Maclure and Willett, 1987].  3.3 RESULTS Alamgir et al. [2006] identified a total of 547 hospital records among the full study population as being work-related using the two indicator variables—E codes and responsibility for payment schedule. A total of 458 records were acute events—identified by urgency or emergency nature of admission, and 391 (85%) of these were found to have matched compensation claims (Figure 3.1). The overall agreement on identifying injury events between the hospital discharge records (two indicators combined) and compensation records was good (k=0.84, PO.01). Among the active sawmill workers, 144 injuries out of 173 hospitalizations were acute in nature. O f these, 129 (90%) were matched to compensation claims (Figure 3.1). The overall agreement between  the hospital records  (two indicators combined) and  compensation records was very good (k=0.87, P<0.01) in this restricted study population. Table 3.2 illustrates how the two work-related indicators in the hospital discharge records agreed with compensation claims for both study populations. The agreement was better across all identifying categories among the active sawmill workers. Overall, the payment field had better agreement with compensation claims than the E codes for identifying work-related injuries. Table 3.3 shows important characteristics of claimed and non-claimed work-related acute injuries requiring hospitalization. Workers employed outside of the sawmills at the time of the injury and older individuals were apparently less likely to file claims for their injury. The injuries with longer length of stay were more likely to be claimed to the workers' compensation system  68  for the actively employed sawmill workers. Relatively fewer serious injuries, defined by emergency admissions, were not claimed, especially among the actively employed sawmill workers. According to the level o f care, injuries requiring day care surgery were more likely to be reported to the compensation system among sawmill workers. Asians, in comparison to the Caucasian population, reported fewer work-related injuries irrespective o f their working status in the sawmill industry. To explore the relationship o f admission category and claim filing patterns further, the records were stratified by admission category and their work-related identifying indicators for both populations (Table 3.4). For emergency cases identified as work-related by payment schedule, almost all cases were claimed. The records identified only by E codes but not b y payment codes regardless o f admission category had poor claim filing patterns. Records identified only by payment codes, but not E codes, for non-emergency admissions also had a poor claim filing pattern. Table 3.5 presents claiming patterns by broad causes o f injury category for both study populations. The most frequent work-related injuries i n both populations were related, falls, struck against, and overexertion.  machinery  In the full study population, among the more  frequent categories o f injury, more than 90% o f work-related hospitalizations for caught in or between, struck by falling object, and machinery related were claimed. Lower claim reporting was observed for work-related hospitalizations involving overexertion; fire, flame, environmental; transportation,  natural &  and falls.  A m o n g the active sawmill workers, close to 100% work related hospitalization cases for cutting & piercing, caught in or between, machinery-related,  struck by falling  object had claims  filed. Lower claim reporting was observed for overexertion and falls. Relatively higher claiming  69  patterns were observed for all major injury categories among the population employed i n sawmills at the time o f injury.  3.4 DISCUSSION Overall, the agreement on work-related injuries identified by hospital discharge records and compensation records was found to be good i n both study populations. This analysis included only injuries that were serious enough to warrant hospitalization, and thus, should have very high claim reporting patterns. However, the study findings suggest that compensation data underreport serious and acute injuries by about 10% even in a population actively working in a large unionized industry in the Canadian province o f B C . Claiming patterns o f hospitalized work-related injury varied by age, race, admission category, level o f care, length o f stay, and causes o f injury. There were very few women in the study populations; thus, it was not possible to examine differences in claiming patterns by sex. The reporting patterns across the two available work related indicators in hospital discharge records were investigated, and the underreporting pattern existed for both. For serious and acute injuries, the responsibility o f payment, when coded as workers' compensation, closely represented compensation reporting. Under claiming was more apparent for injuries that were identified only by the external cause o f injury codes. A l l work-related injuries identified only by E codes might not necessarily be work-related injuries as they identified work places; there might be non-work-related injuries in work places. However, the agreement between the two indicators (E codes and payment fields) o f hospital records i n identifying work-relatedness was found to be good (k=0.75, P<0.01) by the earlier study [Alamgir et al., 2006].  70  Lower reporting was also found among the non-whites and older people, which might be explained by a lack o f their awareness about the compensation system, prior unpleasant experience, higher job insecurity, and greater peer/employer or social pressure. In this study, the more serious injuries, when defined by emergency admission and longer length o f stay, had higher claiming patterns. Underreporting o f work-related injuries by the compensation agencies have been widely studied. Herbert et al. [1999] studied patients diagnosed with work-related carpal tunnel syndrome. O f these patients', only 2 1 % were initially not challenged or received responses from insurers. Insurers were more likely to challenge claims filed by non-white, low wage workers, and union members. Rosenman et al. [2000] interviewed mostly unionized automobile workers, diagnosed with known or suspected occupational repetitive trauma and found only 25.1% o f them filed compensation claims. Workers who consulted a specialist were eight times more likely to file for claims than those who only visited the company doctor. Morse et al. [2001] interviewed 292 Connecticut residents with work-related musculoskeletal disorder among whom, 20.7% were reportedly covered by workers compensation. O f respondents seen by a general practitioner or a family doctor, 11-12% reported coverage by workers compensation. Waller et al. [1989] studied carpenters with work-related injuries at a Vermont hospital in 1986 and 1987. Of  168 non-self-employed subjects,  37% had their hospital bills covered by workers  compensation. Sorock et al. [1993] interviewed 134 former N e w Jersey hospital patients treated for finger or thumb amputations described as work-related. O f these, 19% were not coded as workers compensation in the payment field o f discharge database. A study by Shannon and L o w e [2002], i n Canada also found that lower severity o f injury was the strongest predictor o f not claiming for a work-related injury.  71  The claim patterns also varied by injury categories. Falls, struck against, and especially, overexertion had poor reporting patterns. Injuries that are usually more serious in nature, such as machinery-related, cutting & piercing, caught in or between were found to have more matching claims in the compensation records. This study had a number of limitations in its methodology. A 1-month window beyond admission and separation dates was used for the initial linkage strategy. While this captured primarily acute events needing immediate attention, it relied on the accuracy of dates in both the hospital and compensation records. As well, injuries that were admitted to hospital after a long latent period were excluded from our linking strategy. Using date criterion of 1-day difference for final matching between hospitalization and claim records should have captured the same event in both files, as it is highly unlikely for an individual to sustain two different injuries consecutively with a 1-day difference. A broad injury category rather than exact ICD-9 code was used to match injuries that occurred during the 1-month window between the two data files. This was allowed because the injuries were coded by two different organizations, which should be able to match on broad injury categories but not necessarily on the specifics of the injury. However, an individual might sustain two injuries within the time window, which were of same broad category injury, but were indeed different events. There might be differences in coding accuracy and techniques by the two surveillance systems studied. The hospital records and W C B records had different ways of describing injuries. The W C B provides only one set of ICD-9 codes to describe an injury event; the other injury information they provide including injured body parts and nature of injury, are difficult to verify against other common and standard coding schemes.  72  The W C B file does not provide information on reported claims that are rejected and not compensated. The W C B does not compensate all claims submitted by injured workers. According to annual statistics, 207,019 new injuries were reported i n 1989 and the numbers o f claims first paid i n that year were 153,545 (74%), and i n 1998, 179,582 new injuries were reported in 1989 and the numbers o f claims first paid in that year were 144,380 (80%) [ W C B , 1998]. It was expected that injuries requiring hospitalization should have a higher acceptance rates, and claim filing should have more closely represented compensated claims. The W C B file does not have detailed information on injuries for health care-only claims; thus, alternative variable, such as dates were used to match for claims. The large study population, who were not necessarily working in sawmills at one time, was different from the second population, who were actively working in sawmills at the time o f injury. The latter group, was working full-time i n large, unionized organizations, and should have been comprehensively covered by the workers' compensation system. Higher claim patterns were expected among this group, which the study findings corroborated. According to these findings, the provincial compensation board underreported serious and acute work-related injuries. Several vulnerable groups o f workers and specific injury categories that were associated with greater underreporting were identified. Education and training o f the susceptible group o f workers on the compensation system and claim filing method might help improve reporting patterns. A l s o , compensation claims managers should take precautions to handle claims for the specific injury types that are commonly underreported. This study also suggested that the W C B data collection systems should be upgraded with detailed information on all types o f injuries irrespective o f their severity, and they should follow a more standardized approach o f injury coding as recommended b y I C D - 9 , so that, their data can be  73  effectively used for surveillance. Paying for the costs o f hospitalizations for work-related injuries is the financial responsibility o f the compensation system and nonpayment by them shifts the burden to other parts o f the social safety net (e.g., the publicly funded health care system). The hospital discharge dataset has more detailed information on the type and severity o f injuries than what is traditionally reported and found i n W C B datasets. Moreover, this data is gathered outside o f the contentious arena o f attribution. Depending on coding reliability and validity, hospital discharge data can be a readily available and efficient alternative to provincial compensation body reports for examining serious injury trends and has the potential to be integrated into a comprehensive work-related injury surveillance system in B C . Although B C is unique in terms o f comprehensiveness and access to such datasets, it would be feasible to investigate reporting o f work-related injuries in other jurisdictions for other types o f cohorts or other types o f study populations as long as claim and hospitalization datasets have similar coding scheme and are accessible.  74  T A B L E 3.1: INJURY C A T E G O R Y CREATED F R O M ICD-9 CODES FOR HOSPITAL DISCHARGE RECORDS AND WORKERS' COMPENSATION CLAIMS  iii|uiy uaicuui j  Corresponding ICD-9 Codes  Fracture o f skull & intracranium Fracture-spine & trunk Fracture-upper limb Fracture-femur Other fractures-lower limb Dislocation, sprains, strains Internal injury-chest, abdomen, pelvis Open wounds, injuries to blood vessels Superficial injury, contusion with intact skin surface, crushing Effects o f Foreign body entering thru orifice Burns Nerves and spinal cord Traumatic complications, unspecified, others Toxic effects o f non-medicinal subs  800-804, 850-854 805-809 810-819 820, 821 822-829 830-848 860-869 870-904 910-919, 920-924, 925-929 930-939 940-949 950-957 958, 959, 990-995 980-989  75  T A B L E 3.2: A G R E E M E N T * B E T W E E N W O R K - R E L A T E D INDICATORS IN T H E HOSPITAL RECORDS WITH COMPENSATION C L A I M RECORDS FOR F U L L STUDY POPULATION AND A C T I V E SAWMILL WORKERS  Either E Codes or payment E Codes  391 (85%)  67  458  Active Sawmill Workers Work-related Hospitalizations (144) Matched Not Total with WCB Matched claims with WCB claims 144 129 (90%) 15  340 (87%)  53  393  121 (91%)  12  133  Payment  349 (91%)  36  385  114(93%)  9  123  Both E Codes and payment  298 (93%)  22  320  106 (95%)  6  112  Hospitalizations identified as workrelated by  Full Study population Work-related Hospitalizations (458) Matched Not Matched Total with WCB with WCB claims claims  Kappa* =0.84, PO.01  Kappa* =0.87, PO.01  * Agreement between hospital records (two indicators combined) and W C B claims  76  T A B L E 3.3: IMPORTANT DEMOGRAPHIC AND HOSPITAL CHARACTERISTICS OF T H E HOSPITALIZED INJURY RECORDS STRATIFIED BY CLAIMING PATTERN FOR FULL STUDY POPULATION AND ACTIVE SAWMILL WORKERS "—-—_____ \Characteristic  N Sex (M/F) Race White Asian Length of Stay (Median)  Active Sawmill Workers  Full Study population Total  Work related hospitaliza tion-with matched claims (%)  Workrelated hospitalizatio n- without matched claims (%)  458 454/4  391 (85%) 388/3  67 (15%) 66/1  437 21 3 days  375 (86%) 16(76%) 3 days  62 (14%) 5 (24%) 3 days  P Value  129 (90%) 127/2  Workrelated hospitaliza tionwithout matched claims (%) 15 (10%) 15/0  120 (91%) 9 (75%) 3 days  12 (9%) 3 (25%) 4 days  0.084  Total  Work related hospitalizat ionwith matched claims (%)  144 142/2 0.22  129 15 3 days  0.075  41 [40-43]  P Value  Age (Years) Mean (95% CI) Median Admission Category Urgent Emergency  Level of Care  42 [41-43]  42 [41-43]  44 [42-47]  41  41  43  279 179  233 (84%) 158 (88%)  46(16%) 21 (12%)  56  46 (82%)  10(18%)  0.160  41 [39-41]  41 [36-47]  41  41  42  84 60  72 (86%) 57 (95%)  12 (14%) 3 (5%)  13  12 (92%)  1 (8%)  0.965  0.072  Day Care Surgery  7 7  T A B L E 3.4: ADMISSION CATEGORY AND CLAIM FILING OF HOSPITALIZED INJURY RECORDS BY WORK-RELATED IDENTIFYING INDICATORS FOR FULL STUDY POPULATION AND ACTIVE SAWMILL WORKERS Full Study population Work-related Hospitalizations (458)  Active Sawmill Workers Work-related With matched claims (%)  Hospitalizations (144) Without matched Total claims  Admission Category  With matched claims (%)  Without matched claims  Urgency Emergency  201 (86%) 139(87%)  33 22  234  67 (88%)  9  E Codes  161  54 (95%)  3  Payment  Urgency  206 (88%)  28  234  Emergency  143 (95%) 32 (71%)  8 13  151 45  62 (89%) 52 (98%)  8 1  5 (63%)  19(95%)  1  20  3 0  27 (60%) 15 (54%)  18 13  45 28  Hospitalizations identified as work-related by  Payment but not by E Codes  Urgency Emergency  E Codes but not by payment  Urgency Emergency  Total  76 57 70 53 8  3 (100%) 10(71%)  4  3 14  5 (71%)  2  7  78  T A B L E 3.5: INJURY CATEGORY AND CLAIM FILING OF WORK-RELATED HOSPITALIZED INJURIES Full Study population Work-related Hospitalizations (458)  Cause of Injury (ICD-9 E Codes)  Machinery related (E919) Falls (E880-E888) Struck against (E917) Cutting & piercing (E920) Caught in or between (E918) Struck by falling object (E916) Overexertion (E927) Transportation Injury (E800-E807, E810-E838, E840E848) Explosion, firearms, hot substance, electricity (E921-926) Fire, Flame, Natural & Environmental (E890-E909) Other Poisonings (E860-E869) Drowning, suffocation, foreign body (E910-915) Other & unspecified (E 928) Total  Active Sawmill Workers Work-related Hospitalizations (144) Without Total With matched matched claims claims (%)  With matched claims (%)  Without matched claims  Total  101 (93%) 99 (83%) 34 (87%) 31 (86%) 28 (97%) 26 (93%) 23 (66%) 17 (81%)  8 20 5 5 1 2 12 4  109 119 39 36 29 28 35 21  43 (100%) 21 (84%) 18 (90%) 8 (100%) 9 (100%) 10 (100%) 7 (70%) 3 (100%)  0 4 2 0 0 0 3 0  43 25 20 8 9 10 10 3  14 (88%)  2  16  2 (67%)  1  3  10(63%  6  16  4 (57%)  3  7  4 (100%)  0  4  1 (100%)  0  1  4 (100%)  0  4  3 (100%)  0  3  0 (0%) 391(85%)  2 67  2 458  0 (0%) 129 (90%)  2 15  2 144  79  FIGURE 3.1: CASE IDENTIFICATION OF WORK-RELATED HOPSITALIZATION IN SAWMILL WORKERS  Full Study Population 1,885 injury hospitalizations  547 identified as work-related hospitalizations hospitalizations  Active Sawmill Workers 370 injury hospitalizations  173 identified as work-related  I 458 work-related acute hospitalizations  144 work-related acute hospitalizations  I 399 hospitalizations linked to compensation claims within 1 month of admission or separation date  391 hospitalizations matched within 1 day of admission date and/or type of injury  141 hospitalizations linked to compensation claims within 1 month of admission or separation date  129 hospitalizations matched within 1 day of admission date and/or type of injury  80  3.6 REFERENCES Alamgir H , Koehoorn M , Ostry A , Tompa E , Demers P. 2006.An evaluation o f hospital discharge records as a tool for serious work related injury surveillance. Occup Environ M e d 63:290-6.  Azaroff L S , Levenstein C,Wegman D H . 2002. Occupational injury and illness surveillance: Conceptual filters explain underreporting. A m J Public Health 92:1421-1429.  Biddle J, Roberts K , Rosenman K D , W e l c h E M . 1998. What percentage o f workers with workrelated illnesses receive workers' compensation benefits? J Occup Environ M e d 40:325-331.  B C Ministry o f Health. 2004. Medical Services Plan, Quick Facts 2003/2004. http://www.healthservices.gov.bc.ca/ msp/quickfacts.html. Accessed October 02, 2004.  B C Statistics. 2005. Labour Force Data for British Columbia and Canada. February 2005. http://www.bcstats.gov.bc.ca/ data/lss/lfs/bccanlfs.pdf. Accessed M a r c h 28, 2005.  CIHI. 1999. Canadian Institute for Health Information. The C C I C D - 1 0 Implementation Tool K i t , 1999, 7.  C H S P R . 2004-A. Centre for Health Services & Policy Research. B C Linked Health Database, http://www.chspr.ubc.ca/Bclhd/aboutbclhd.htm. Accessed October 02, 2004.  C H S P R . 2004-B. Centre for Health Services & Policy Research. B C Linked Health Database, Workers' Compensation Board File. http://www.chspr.ubc.ca/Bclhd/codetables/wcb.htm. Accessed October 02, 2004.  Chamberlayne R, Green B , Barer M L , Hertzman C , Lawrence W J , Sheps S B . 1998. Creating a population-based linked health database: A new resource for health services research. Can J Public Health 89:270-273.  81  Frumkin H , Williamson M , M a g i d D , Holmes J H , Grisson J A . 1995. Occupational injuries in a poor inner-city population. J Occup Environ M e d 37:1374-1382.  Hayden G J , Gerberich S G , Maldonado G . 1995. Fatal farm injuries: A five-year study utilizing a unique surveillance approach to investigate the concordance o f reporting between two data sources. J Occup Environ M e d 37:571-577.  Herbert T, Janeway K , Schechter C . 1999. Carpal tunnel syndrome and workers' compensation among an occupational clinic population in N e w Y o r k State. A m J Ind M e d 35:335-342.  Hertzman C , Teschke K , Ostry A , Hershler R, Dimich-Ward H , K e l l y S, Spinelli JJ, Gallagher R P , M c B r i d e M , M a r i o n S A . 1997. Mortality and cancer incidence among sawmill workers exposed to chlorophenate wood preservatives. A m J Public Health 87:71-79.  I C D - 9 - C M . International Classification o f Diseases, Ninth Revision, Clinical Modification. U S Department o f Health and Human Services. Hyattsville, M D .  M a c lure M , Willett W C . 1987. Misinterpretation and misuse o f the kappa statistic. A m J Epidemiol 126:161-169.  M c C u r d y S A , Schenker M B , Samuels SJ. 1991. Reporting o f occupational injury and illness i n the semiconductor manufacturing industry. A m J Public Health 81:85-89.  Morse T, D i l l o n C,Warren N , H a l l C , H o v e y D . 2001. Capture-recapture estimation o f unreported work-related musculoskeletal disorders in Connecticut. A m J Ind M e d 39:636-642.  Murphy P L , Sorock G S , Courtney T K , Webster B S , Leamon T B . 1996. Injury and illness i n the American workplace: A comparison o f data sources. A m J Ind M e d 30:130-141.  82  Rosenman K D , Gardiner J C , Wang J, Biddle J, Hogan A , R e i l l y M J , Roberts K , Welch E . 2000. W h y most workers with occupational repetitive trauma do not file for workers' compensation. J Occup Environ M e d 42:25-34.  Shannon H S , L o w e G S . 2002. H o w many injured workers do not file claims for workers' compensation benefits? A m J Ind M e d 42:467-473.  Sorock G S , Smith E , H a l l N . 1993. A n evaluation o f N e w Jersey's hospital discharge database for surveillance o f severe occupational injuries. A m J Ind M e d 23:427-437.  Stanbury M , Joyce P, K i p e n H . 1995. Silicosis and workers' compensation in N e w Jersey. J Occup Environ M e d 37:1342-1347.  Tercero F , Andersson R. 2004. Measuring transport injuries in a developing country: A n application o f the capture-recapture method. A c c i d A n a l Prev 36:13-20.  Teschke K , Ostry A , Hertzman C , Demers P A , Barroetavena M C , Davies H W , Dimich-Ward H , Heacock H , M a r i o n S A . 1998. Opportunities for a broader understanding o f work and health: multiple uses o f an occupational cohort database. Can J Public Health 89:132-6.  van CharanteAW, Mulder P G . 1998. Reporting o f industrial accidents in The Netherlands. A m J Epidemiol 148:182-190.  Waller J A , Payne S R , Skelly J M . 1989. Injuries to carpenters. J Occup M e d 31:687-692.  W C B . 1998. Workers; Compensation Board o f British Columbia. Statistics, 98. http://www.worksafebc.com/Publications/reports/statistics_reports/ assets/pdf/stats 1998.pdf. Accessed March 28, 2004.  83  CHAPTER 4 ACCURACY OF INJURY CODING IN A CANADIAN WORKERS' COMPENSATION SYSTEM  3  4.1 INTRODUCTION Information on work-related injuries filed for compensation are routinely collected and coded by the workers' compensation systems. Workers' compensation data have been used by health services and population health researchers to study the incidence, epidemiology, outcomes  and costs  o f work-related injury, and also to investigate  the  effectiveness,  appropriateness, and utilization o f the services provided by compensation systems [ M c C a l l et al., 2006; Horwitz et al., 2005; Scherzer et al., 2005; Boufous et al., 2003; Islam et al., 2001]. The use o f workers' compensation data for research purposes is based, however, on the assumption that it provides reasonably valid information on injury related diagnoses. Evaluation o f the validity o f the workers' compensation system dataset is imperative because this data source provides the most comprehensive source o f information on work-related injuries to date. Hospital discharge records i n the Canadian province o f British Columbia ( B C ) have the potential to be a useful data resource for injury surveillance because o f the public health care system i n Canada and the comprehensive coverage o f hospitalizations at the population level. Hospital discharge data is also a potential source o f information on serious work-related injuries. External cause o f injury codes (E-codes) o f the International Classifications o f Disease and source o f payment information are available i n hospital discharge records to identify the work-  3  The chapter is currently under review for publication in Journal of Occupational Health  & Safety Australia and  New Zealand under the same title.  84  relatedness o f an injury hospitalization i n British Columbia ( B C ) , Canada [ICD-9; Alamgir et al., 2006]. Since A p r i l 1989, the hospitals i n B C started coding an additional digit to the ICD-9 schedule that enhanced its utility as a work-related injury surveillance system [Alamgir et al, 2006]. It is expected that most o f the work-related injury cases that are hospitalized should have been compensated and have matching claims in the workers' compensation datasets. Thus, hospital discharge records provide an opportunity to evaluate the injury coding patterns o f the workers' compensation system for serious injuries reaching hospitals. The validity o f the injury related diagnostic codes o f the workers' compensation dataset was assessed i n this study using the hospital discharge dataset as the comparative standard. The injuries admitted to hospitals through urgent and emergency departments are usually more acute in nature. W e , therefore, hypothesized that the compensation system codes should agree with the hospital diagnosis codes for these work-related injuries. This study also examined the agreement o f the injuries by body parts involved between these two data sources. The study population for this study was a large cohort study o f B C sawmill workers that was started i n the 1980's to investigate the risk o f cancer associated with the use o f Chlorophenol fungicides and later expanded to examine other health issues in the industry [Hertzman et al., 1997; Teschke et al., 1998].  4.2 M E T H O D S A N D D A T A S O U R C E S Hospital discharge records and workers' compensation records for this study came from the British Columbia Linked Health Database ( B C L H D ) . The B C L H D is a health data resource for research purposes created and maintained by the University o f British Columbia's Centre for Health Services and Policy Research ( C H S P R ) . It contains datasets recording physician visits, hospital discharges, deaths, births, as well as extended care, drug usage, and workers'  85  compensation claims since 1985 [ C H S P R , 2005]. The datasets are linked to a central registry file of all persons i n the province covered by the B C Medical Services Plan ( M S P ) [ C H S P R , 2005]. Almost all eligible residents o f B C (over 4.1 million people) are enrolled with the provincial Medical Services Plan ( M S P ) [ B C Ministry o f Health, 2005]. The M S P processes claims for insured services submitted by physicians, supplementary health care practitioners, hospitals, laboratory services and diagnostic procedures [ B C Ministry o f Health, 2005]. A s part o f previous investigations, among the 6,512 cohort members actively employed on or after A p r i l 01, 1989, a total o f 5, 876 members were linked with their health records using the B C L H D as o f A p r i l 01, 1989. Hospitalization records were extracted for this study population and identified as work-related or not. These were identified as work-related using I C D - 9 external cause o f injury codes that indicate place o f occurrence, and the responsibility o f payment schedule, which identifies workers' compensation as being responsible for payment. The methods are described by Alamgir and colleagues [2006]. The principal I C D - 9 diagnosis for the patient's stay i n a hospital was used to designate the nature o f the injury, and each hospitalization record was then categorized into meaningful broad nature o f injury categories. The principal ICD-9 codes were also used to identify the exact body parts involved in an injury. The body parts were also categorized into meaningful broad body part categories. For example, an ICD-9 code o f 801 is a fracture o f base o f skull. The nature o f injury is fracture o f head and the body part is head. The B C L H D has information on all claims reported and compensated by the Workers' Compensation Board o f B C ( W C B ) from the year 1987 onwards [ C H S P R , 2004]. C l a i m records have information on injury date, ICD-9 codes, source o f injury, nature o f injury, and the body  86  parts involved. To compare with hospital data, the reported I C D - 9 codes and body parts o f the W C B records were also categorized into similar broad nature o f injury and body parts categories. To identify the claim record for a particular hospitalized injury event, the claim records for this study population were extracted from 1989 to 1998. The date o f injury recorded in the claim record for an injured individual and the dates o f admission and separation in the hospital record for the same individual was used to link these two datasets. For an individual, i f the date of injury o f the claim record fell within the range o f one week prior to hospital admission date to one week after the hospital separation date, it was considered the same injury event. For example, i f the hospital admission and separation dates were A p r i l 8 and A p r i l 18, a claim record with an injury date recorded anywhere between A p r i l 1 and A p r i l 25 would be considered the same injury event. The  ICD-9 codes o f both the hospital discharge database and compensation claims  database were studied by exact ICD-9 diagnosis four digits codes, by 3 digits, then by 2 digits, and finally, by the broad nature o f injury. The body sites were also investigated. Holding the hospital discharge records as the standard, sensitivity, specificity, positive and negative predictive values o f the compensation records were calculated. Kappa was also calculated to measure the agreement between both data sources [Sim and Wright, 2005]  4.3 RESULTS A total o f 1,595 urgent and emergent hospitalization records were extracted for injury diagnosis between A p r i l 1989 and December 1998 for this study population. B y using the two indicator variables- E codes and responsibility for payment schedule, 458 hospitalizations (29%)  87  were identified as work-related. A total o f 333 (73%) o f these were found to have matched compensation claims by 1 week window.  4.3.1 AGREEMENT BY NATURE OF INJURY Between the compensation claims data and hospital discharge data, a total o f 107 records matched on the 4 digit I C D - 9 code (32%); whereas 162 matched on the 3 digit ICD-9 code (49%). A l s o , a total o f 228 records matched on the 2 digit ICD-9 code (69%). When compared by injury characteristics, 232 injury events matched on nature o f injury (70%). Table 4.1 shows the frequency o f the injuries and agreement statistics by the two data sources based on the broad injury category. The workers' compensation claims only agreed with the hospitalization database for 1 o f 9 (11%) o f internal injury of thorax, abdomen & pelvis and injuries of nerves & spinal cord and 5 o f 18 (28%) o f the traumatic complications, non-medicinal substances, unspecified & other injuries. A l s o , only 78% o f the cases o f fracture o f lower limbs were reported by the workers' compensation database. In contrast, the compensation database detected 34 (136%) more cases o f superficial injury, contusion & crushing injuries than the hospitalization database. To determine the extent to which the hospitalization database and the compensation claims database identified the same injury cases (i.e., inter-database agreement), we computed kappa for each o f the conditions. The highest level o f agreement (K = 0.97) was found for burns, with excellent agreement for fracture of lower limbs. The lowest level o f agreement was found for internal injury of thorax, abdomen & pelvis and injuries of nerves & spinal cord; superficial injury,  contusion  &  crushing  and  traumatic  complications,  non-medicinal  substances,  88  unspecified  & others. The levels o f agreement were good (0.63-0.74) for the remaining  conditions. Assuming the hospitalization database correctly identified the conditions as being present or absent, sensitivity, specificity, and predictive values were calculated (Table 4.1). The results indicate that the  compensation  database was  hospitalization database indicates they were  most  likely to identify burns when  the  truly present (sensitivity). Conversely, the  compensation database was least likely to identify traumatic  complications,  non-medicinal  substances, unspecified & other injuries and failed to identify internal injury of thorax, abdomen & pelvis; and injuries of nerves & spinal cord. The positive predictive values for fracture of lower limbs and burns were more than 90%, indicating good evidence o f these conditions when these were coded as such in the compensation database relative to the hospitalization source o f information.  4.3.2 AGREEMENT BY T H E BODY PARTS OF INJURY Table 4.2 shows the prevalence o f injury categories by body parts for the two data sources. Compared to hospitalization database, the compensation database detected only 70% o f shoulder & arm injuries and 80% o f trunk, back & groin injuries. It captured about 90% head, face & neck and leg, knee & ankle injuries. In contrast, the compensation database detected 11 more hand & finger injuries (10%) and 11 more other body parts injuries (30%) than the hospitalization database. The highest level o f agreement (K = 0.86) was found for leg, knee & ankle injuries, with very good agreement for hand & finger and head, face & neck injuries. The lowest level o f agreement was found for shoulder & arm and other body parts injuries.  89  Assuming the hospitalization database correctly identified the conditions as being present or absent, sensitivity, specificity, and predictive values were calculated (Table 4.2). The results indicate that the compensation database were most likely to identify hand/finger injuries when the hospitalization database indicates they were truly present (sensitivity). Conversely, the compensation database was least likely to identify shoulder/arm injuries. The positive predictive value for leg, knee & ankle; head, face & neck, hand & finger and trunk, back & groin were more than 80%, indicating good evidence o f these conditions when these were coded i n the compensation database relative to the hospitalization source o f data.  4.4 DISCUSSION This study, to our knowledge, is the first to evaluate the accuracy o f injury coding in the compensation data among a population o f injured workers admitted to hospitals. The results indicate that the overall agreement o f injury coding between the compensation dataset and hospitalization dataset was good; Kappa was 0.63 for nature o f injury and 0.71 for body parts. Kappa measured the amount o f agreement beyond what is expected due to chance alone [Sim and Wright, 2005]. This study encourages the use o f compensation datasets for occupational epidemiology and injury surveillance investigations. This support is stronger for more acute and sharp injuries such as burns and fracture superficial injuries  injury, contusion & crushing;  of nerves & spinal  unspecified  of lower limbs and weaker for injuries such as internal  cord and traumatic  injury of thorax, abdomen & pelvis complications,  non-medicinal  and  substances,  & others. For body parts, high level o f agreement was found for leg, knee & ankle,  hand & finger and head, face & neck and low level o f agreement was found for shoulder & arm and other body parts injuries.  90  The hospitalization database was used as the standard to compare the claim database in our study as the reliability and validity o f hospital records were favorably examined previously by some studies [Vestberg et al., 1997; Rawson and M a l c o l m , 1995; Kashner, 1998; Beghi et al., 2001]. C l a i m records are usually more concerned about cost information and industry o f employment fields because these are used to determine employer payments/premiums and the other fields are secondary for statistics and report generation, and as a result, there is  less  incentive to be exact compared to hospitalizations i n injury diagnosis. L i k e any other administrative dataset, errors could occur in the process o f creating the workers'  compensation  dataset  as  a  result  of  physicians'  misdiagnoses,  incomplete  documentation o f clinical information, or coders' incomplete or miscoding o f diagnoses [Johantgen et-al., 2004; Maclntyre et al., 1997; Hawker et al., 1997; Tamblyn et al., 2000; Quan et al., 2004]. A l s o , there could be multiple organs affected in some injury events making the coding o f one primary reason or site very difficult. This study had a number o f limitations in its methodology. A one-week window beyond admission and separation dates was used for the linkage strategy. While this captured primarily acute events needing immediate attention, it relied on the accuracy o f dates i n both the hospital and compensation records. A s well, injuries that were admitted to hospital after a long latent period were excluded from our linking strategy. Using date criterion o f one-week difference for matching between hospitalization and claim records should more likely capture the same event in both files as it is highly unlikely for an individual to sustain two different injuries i n a row within this short period. However, i f we used a narrower time window, the agreement should have improved.  91  This study was not also able to describe the reasons why injuries of some nature and body parts were associated with low level of agreement between the two data sources. Limited studies done in this area restricted further interpretations. Another limitation was that all injuries studied here were sawmill injuries. Using a larger study population comprising of workers from other industrial sectors would have been able to study other types of injuries, and provide more support to the findings on validity of injury coding in the claims datasets. A broad injury category rather than exact ICD-9 code was used to match injuries between the two data files in this study. This was allowed because the injuries were coded by two different organizations; this should allow for a match on broad injury categories but not necessarily on the specifics of the injury. As was expected the agreement was the best for broad injury category, then gradually decreased for comparison of the specific ICD9 codes from 2 digits to 4 digits. The W C B provides other injury information that is difficult to verify against sources like hospitals which use more standard coding schemes. It was not possible to match cases by causes of injury, as the causes available in the compensation databases were very different from the standard ICD-9 external cause of injury codes. The cause of injury categories created by using the ICD-9 external cause codes from hospital discharge database were falls, struck by falling object, caught in or between, cutting & piercing,  cutting and piercing,  etc., whereas, the  compensation systems categorized injures based on contacts with animals  (live), boxes,  containers, glass items, liquids, trees, plants, working surfaces, etc.  It should be kept in mind that this study was undertaken independently of the workers' compensation or medical care system and without any prior agreement regarding definitions for coding information in the two data sources. Discrepancies are thus likely to occur. The ultimate  92  gold standard for comparison would be clinical data collected prospectively i n accordance with rigorous, a priori definitions as occur in the setting o f a clinical trial. Despite the favorable comparison between data from the hospitalization database and compensation databases, this study cannot establish the true validity o f clinical data from the compensation databases because hospitalization database is not the perfect gold standard, but the agreement between these two independent sources o f data lends some credence to the clinical information that can be ascertained from claim records. The validity o f injury diagnosis i n administrative datasets has been studied before, and in most previous studies, the comparator group was not another set o f administrative data but rather patient charts or surveys [Johantgen et al., 2004; Maclntyre et al., 1997; Hawker et al., 1997; Tamblyn et al., 2000; Quan et al., 2004]. The accuracy o f diagnostic codes for workers' compensation system has rarely been investigated  before.  However, workers  compensation  database  should  follow  a  more  standardized approach o f injury coding as recommended by I C D - 9 or ICD-10, so that their datasets can be more effectively used for surveillance and compared with other readily available data sources. The structure and operation o f provincial hospitalization databases across Canada are similar. A l l provinces and territories follow guidelines from the Canadian Institute o f Health Information [CIHI, 2006]. The workers' compensation datasets o f other provinces also follow similar coding scheme [ A W C B C , 2006]. It is, therefore, likely that findings like these on coding accuracy have wider generalizability across Canada.  93  T A B L E 4.1: MEASURES OF A G R E E M E N T BETWEEN COMPENSATION CLAIMS DATA AND HOSPITAL DISCHARGE DATA BY NATURE OF INJURY  Nature of injury Open wounds Fracture of lower limbs Fracture of upper limbs Spine & trunk Dislocation, sprains & strains Superficial injury, contusion & crushing Burns Traumatic complications, non-medicinal substances, unspecified & others Internal injury of thorax, abdomen & pelvis; Injuries of nerves & spinal cord Total  Negative Predictive Value  Kappa  0.79 0.96  0.93 0.94  0.72* 0.81*  0.95  0.74  0.95  0.69*  0.70  0.94  0.67  0.95  0.63*  28 (8.4)  0.78  0.98  0.75  0.98  0.74*  25 (7.5)  59(17.7)  0.60  0.86  0.25  0.96  0.28*  15 (4.5) 18(5.4)  16 (4.8) 5(1.5)  1.00 0.22  1.00 1.00  0.94 0.80  1.00 0.96  0.97* 0.33*  9 (2.7)  1 (0.3)  0.00  1.00  0.00  0.97  0.00  333  333  Specificity  Frequency in Hospital Data 76 (22.8) 64 (19.2)  Frequency in Compensation data  Sensitivity  73 (21.9) 50(15)  0.76 0.75  0.94 0.99  53 (15.9)  53 (15.9)  0.74  46(13.8)  48 (14.4)  27 (8.1)  Positive Predictive Value  0.64*  * Statistical significance at 95% level  94  T A B L E 4.2: MEASURES OF A G R E E M E N T B E T W E E N COMPENSATION CLAIMS DATA AND HOSPITAL DISCHARGE DATA BY BODY PARTS N3ody Parts  Hand& Finger Leg, Knee & Ankle Trunk, Back & Groin Head, Face &Neck Shoulder & Arm Other body parts Total  Frequency in Hospital Data 110(33)  Frequency in Compensation data 121(36.3)  82 (24.6)  75 (22.5)  50(15)  40(12)  44(13.2)  42(12.6)  10(3) 37(11.1) 333  Positive Predictive Value  Negative Predictive Value Kappa 0.84 *  Sensitivity  Specificity  0.94  0.92  0.85  0.97  0.85  0.98  0.93  0.95  0.64  0.97  0.80  0.94  0.82  0.98  0.86  0.97  0.30  0.99  0.43  0.98  0.38  0.89  0.29  0.92  0.86* 0.67* 0.81* 0.34*  7(2.1) 48 (14.4)  0.23*  333  0.71*  Statistical significance at 9 5 % level  95  4.6 R E F E R E N C E S  Alamgir H , Koehoorn M , Ostry A , Tompa E , Demers P. 2006. 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Teschke K , Ostry A , Hertzman C , Demers P A , Barroetavena M C , Davies H W , Dimich-Ward H , Heacock H , M a r i o n SA.1998. Opportunities for a broader understanding o f work and health: multiple uses o f an occupational cohort database. Can J Public Health 89:132-6.  Vestberg K , Thulstrup A M , Sorensen H T , Ottesen P, Sabroe S, Vilstrup H . 1997. Data quality o f administratively collected hospital discharge data for liver cirrhosis epidemiology. J M e d Syst. 21:11-20  98  CHAPTER 5 COSTS AND COMPENSATION OF WORK-RELATED INJURIES IN BRITISH COLUMBIA SAWMILLS  4  5.1 INTRODUCTION Severe and non-fatal injuries often require hospitalization. These injuries have the highest potential o f resulting in both short and long-term disability, and are among the most costly o f all injuries from an economic perspective. When injuries requiring hospitalizations are workrelated, they typically involve substantial losses o f productivity for the injured worker. Cost o f injury studies are important for providing information on 1) the economic burden o f injuries; 2) the comparison o f cost burdens o f different injuries and diseases; 3) the cost to be incorporated into cost-effectiveness  analysis; 4) the most important cost components o f specific injuries  warranting research on treatment options and prevention efforts; and 5) the trends in costs and projection o f future costs [Koopmanschap, 1998; W e i l , 2001]. Costs o f work-related injuries in the U S A have been studied within states [Leigh et al., 2001], across states [Waehrer et al., 2004], across industries [Leigh et a l , 2004], and within the health services sector [Waehrer et al., 2005], but little attention has been paid in Canada to the costs generated b y such injuries, much o f which are preventable. Most o f the cost statistics on work-related injury i n Canada have been based on reports from workers' compensation agencies, but these agencies do not capture all work-related injuries nor do they cover all associated costs [Shannon and Lowe, 2002; W C B , 2005-A]. Therefore, it is 4  The chapter is currently under review for publication i n Occupational and  Environmental Medicine under the same title.  99  invaluable to study costs using injury reports from an independent surveillance source to obtain a more comprehensive account o f serious injuries. Additionally, estimating costs using an independent source and comparing the findings with the results reported by the workers' compensation systems w i l l reveal the magnitude o f the burden shifted to other social safety i  systems. Hospital discharge records from provincial health care providers can be a useful resource for  serious injury surveillance because the public health care system i n Canada provides  comprehensive coverage o f hospitalizations at the population level. W e use data from British Columbia ( B C ) to illustrate its potential. Almost all eligible residents o f B C (over 4.1 million people) are enrolled with the provincial Medical Services Plan ( M S P ) [ B C Ministry o f Health, 2005]. The M S P captures all medical services records o f physicians, specialists, other health care practitioners, laboratory services, and diagnostics services and hospitalizations. The hospital discharge dataset is a potential source o f information on serious work-related injuries. External cause o f injury codes and source o f payment information are available in hospital discharge records and can be used to identify work-relatedness o f an injury requiring hospitalization [Alamgir et al., 2006-A]. Since A p r i l 1989, hospitals in B C started coding an additional digit to the International Classifications o f Disease diagnosis schedule that enhanced its utility as a work related injury surveillance system [Alamgir et al., 2006-A]. Most employers in B C are required by law to register their business/firm with the workers' compensation system and pay premiums [ W C B , 2005-B]. Employer coverage is usually more comprehensive for large, high-risk, and unionized industries. If a worker experiences a work-related injury or illness the compensation system is required to pay for incurred medical expenses (both medical services and supplies), wage-loss benefits, and any  100  necessary rehabilitation services [ W C B , 2005-A]. The compensation system also provides pension benefits to permanent disabled workers [ W C B , 2005-A]. Sawmills in British Columbia provide an important work-setting to study the costs o f work-related injury as this sector is large and unionized, contributes significantly to the economy o f the province, is a relatively hazardous industry, and its workers are covered by the provincial compensation system. Further, a large cohort study on sawmill workers exists i n B C , initiated i n the 1980's to investigate the risk o f cancer associated with the use o f Chlorophenol fungicides [Hertzman et a l , 1997], and later expanded to investigate a wide variety o f occupational health issues i n the forest industry [Teschke et al., 1998]. The objectives o f this study were to assess the costs o f serious work-related injuries requiring hospitalization amongst the active sawmill workers in British Columbia during 19891998 from the perspective o f the workers' compensation insurer. W e estimated both workers' compensation costs paid by the compensation system and those costs that should have been paid but were not (i.e., the hospital discharge cases not identified i n the workers' compensation records).  5.2 METHODS AND DATA SOURCES The current investigation examined a sub-set o f the full B C sawmill cohort, who were actively working i n the study sawmills at the time o f a hospital admission. Hospital discharge records and workers' compensation claims for this study population came from the British Columbia Linked Health Database ( B C L H D ) . The B C L H D is a health data resource for research purposes created and maintained by the University o f British Columbia's Centre for Health Services and Policy Research. It contains datasets recording physician visits, hospital discharges, deaths, births, as well as extended care, drug usage, and workers' compensation claims since  101  1985 [ C H S P R , 2004]. The datasets are linked to a central registry file o f all persons in the province covered by the B C Medical Services Plan [Chamberlayne et al., 1998]. A s part o f previous investigations [Alamgir et al., 2006-A], we were able to link 5,876 o f 6,512 cohort members (90.3%) actively employed in sawmills on or after A p r i l 01, 1989, with their medical services and hospitalization records using the B C L H D . Work-related injuries were captured among these sawmill workers using the hospital discharge dataset. Hospitalization records were identified as work-related using I C D - 9 external cause o f injury codes that indicate place o f occurrence and the responsibility o f payment schedule, which identifies workers' compensation as being responsible for payment. The methods are described by Alamgir et al [2006-A]. The principal diagnosis for the patient's stay in a hospital was used to designate the nature o f work-related injury, and each hospitalization record was then categorized into meaningful broad nature o f injury categories. External cause o f injury (ICD-9 E codes) was used to designate the cause o f work-related injury, and each hospitalization record was then categorized into meaningful broad cause o f injury categories. The B C L H D has information on all injuries and illnesses compensated by the workers' compensation agency o f B C [ C H S P R , 2004]. C l a i m records had information on injury date, I C D - 9 codes, source o f injury, nature o f injury, and the body parts involved. The compensation claim records for this study population were extracted from and matched with the work-related injury hospitalization records by worker study identifier, injury date relative to the admission and separation dates, and ICD-9 codes o f the hospital discharge records with the ICD-9 codes o f the compensation  claim records  [Alamgir et al., 2006-B]. For each matched  injury claim,  comprehensive compensation cost data for up to 7 years was collected directly from the W C B .  102  The claim cost information was classified b y type o f compensation benefits: health care only, short-term  disability  (time-loss),  long-term  disability  (permanent  disability), vocational  rehabilitation and fatality. A s noted, costs were calculated from the workers' compensation agency perspective. Costs incorporated i n the analysis include short and long-term wage replacement costs, hospital care service costs, and rehabilitation costs. Costs for short-term and long term-disability and vocational rehabilitation were aggregated into non-healthcare costs for some analyses. A l l costs were converted into constant Canadian dollars with 1995 as the base using the provincial general consumer price index (CPI) for the non-healthcare costs and medical consumer price index for the healthcare costs [Drummond et al., 1997]. A 5% discounting rate was applied to adjust for the time value o f money and all values were discounted to 1995 [Drummond et al., 1997]. For the uncompensated cases, costs were imputed from the compensated cases using the median cost for a similar nature o f injury. Total costs and median costs were calculated by cause and nature o f injury. The portion o f costs that the workers' compensation agency did not appear to compensate were also reported.  5.3  RESULTS  For the 5,876 active sawmill workers, there were 370 injury hospitalization events captured between 1989 and 1998. B y either o f the two indicators (E Codes or payment schedules), 173 (47%) o f the hospitalizations were identified as work-related. O f these 173 hospitalizations, 136 (79%) were matched to a compensation claim. Thus, 37 (21%) o f the workrelated injuries requiring hospitalization were not matched to a workers' compensation claim.  103  Approximately 95% o f the work-related injuries requiring hospitalization resulted in a short-term-disability claim and about one-half o f the injuries also resulted i n a long-term disability claim (calculations excludes the 37 that were not in the W C B records). However, only 13% o f the 136 hospitalized injuries required vocational rehabilitation. Figure 5.1 shows claim outcome categories by cause and nature o f work-related injury. About 89% o f caught in or between, 75% of fire, flame, natural & environmental,  67% oi cutting and piercing and 63% o f  machinery related injuries resulted in long-term disability. In terms o f nature o f injury, 83% o f the fracture of upper limb, 83% o f the open wounds, 83 % o f the burns and 65% o f the fracture of lower limb resulted in long-term disability. Table 5.1 lists the median and total costs for all 173 work-related injuries requiring hospitalization among this study population stratified by compensation benefit category. The median cost o f a work-related injury was almost $20,000. In terms o f total costs, the most expensive cost category was long-term disability (almost half o f total costs); they were also associated with the highest median costs. Table 5.2 lists the median and total costs for healthcare and non-healthcare expenses for all work-related injury categories among the study population. B y median costs, the category o f fire, flame, natural & environmental  was the most costly cause o f injury and the category o f  open wounds was the most costly nature o f injury for both non-healthcare and health care costs. In terms o f total costs, the category o f machinery related injuries was the most costly cause o f injury, and the category o f open wounds remained the most costly category for nature o f injury for both non-health care and health care costs. Figure 5.2 depicts the compensation patterns o f the identified work-related injuries. The injuries without a workers' compensation claim were associated with $874,871(8.4% o f total) o f  104  non-health care costs and $200,588 (11.4%) o f healthcare costs. In total $1,075,459 (9%) was not compensated by the workers' compensation system.  5.4 DISCUSSIONS This study described costs and compensation patterns o f work-related serious injuries requiring hospitalization among the sawmill workers in British Columbia. W e estimated costs using data from the provincial compensation system for healthcare (medical services) and nonhealth care services (vocational rehabilitation, permanent disability payments and lost-time payments). Our study found median non-health care costs o f $16,559 and healthcare costs o f $4,377 per injury and total non-health care costs o f $10,374,115 and healthcare costs o f $1,764,137. Comparison o f cost statistics across studies is very difficult because o f differences in the healthcare system, compensation patterns and coverage, components o f costs included, and workforce and industries studied. Some other studies around the world have quantified the economic burden o f injuries. Waehrer and colleagues [2004] estimated occupational injury costs per worker across states in the U S A . Analysis was conducted on injury data from the Bureau o f Labor Statistics and costs data from workers' compensation records. In the state o f Washington, the costs o f nonfatal cases with at least 1 day o f work loss per employee was found to be $864. Eastridge and colleagues [2006] analyzed costs o f motorcycle related injuries i n Texas and estimated charges o f $36,334 $39,390 per injury. Sorensen and colleagues [2006] studied the economic consequences o f nursing home falls in the U S A . The most costly was fall category with multiple injuries, which accounted for $ 22,368.  105  Rautiainen and colleagues [2005] aimed to determine the cost burden from compensated injuries in Finnish agriculture using workers compensation records. The mean cost o f 1996 injury cases was estimated at Euro  1,340. Small and colleagues [2006] examined the  demographics, injury profile, and cost o f pedestrian accidents in a central city hospital i n Sydney. The average length o f stay was 13.4 days costing $ A 16,320 per admission. Singh and colleagues [2006] studied head injuries through a prospective 6-month study to evaluate the expenditure incurred on head injury patients i n a modern neurosurgical center in India. The total expenditure in minor head injury was Rs. 7,800 per patient, i n moderate head injury was Rs. 22,172 per patient, whereas in severe head injury, it was found to be Rs. 32,852 per patient. Patients who underwent surgery, the total cost incurred was Rs. 33,100 per operated patient. [1 Indian rupee = 0.02 U . S . dollars] Nilsen and colleagues [2006] reviewed studies that calculated injury costs. Based on 12 studies that met the inclusion criteria, the average total cost per injury case was found U S D $3,536, while the average share o f indirect to total cost per injury case was 71%. Our estimates o f costs are likely to be underestimates o f societal costs because we took the perspective o f the workers' compensation agency. This perspective ignores costs such as those associated with pain and suffering as well as those related to home care, lost leisure time, out o f pocket expenses for the worker or spouse/family members; ambulance fees, retraining, recruiting, and overtime costs for the employers [Weil, 2001; Drummond et al., 1997]. While it is recommended to calculate costs o f an illness or injury from the societal perspective so that all costs are included irrespective o f where the burden falls [Drummond et al., 1997], there was insufficient information available for us to consider all costs i n this study. The W C B covered health care costs for a compensated injury including the medical services and supplies required  106  to help the worker recover from a compensable injury [ W C B , 2005-A]. Long-term disability costs apply to work-related injury or disease that permanently disables a worker [ W C B , 2005A ] . The W C B covered vocational rehabilitation program helps disabled workers get back to work after a compensable injury [ W C B , 2005-A]. Thus, the W C B covers some important cost components associated with an injury. The costs captured in this study included these important costs associated with a work-related injury. This study calculated costs for different injury categories and ranked them. For example, according to our findings, preventing only one burn injury could save about $54,000 for the compensation agency. A s well, our findings suggest a prevention focus on open wounds, machinery related and fire & environmental  causes are a key area to focus on i f a significant  reduction in work-related injury burden is being sought. According to the workers' compensation board statistics, there were 28,950 full-time equivalent sawmill workers with insurance coverage in B C i n 1997 who sustained a total o f 1,737 time-loss injuries at work [ W C B , 2005-C]. I f we assume that all time-loss injuries resulted in hospitalization and were similar i n costs, according to our findings, based on a median cost o f $19,506, the total costs for this sector are estimated at $33,881,922 in 1995 constant dollars. According to the official statistics, the reported costs were 34.1 million to the Board in 1997 dollars suggesting that our predicted results were very close to the official costs. The strength o f this study was the use o f a readily available and large administrative datasets. Our study also captured actual compensated costs for each claim rather than estimating these from secondary sources or using average claim costs. This study used distinct C P I indexes for healthcare costs and non-healthcare costs for B C province to account for the inflation. It also  107  used a 5% discount rate to adjust for the time value o f money. Sensitivity analyses with rates o f 3% through 7% would also result i n substantial cost burdens. This study had a number o f limitations i n its methodology. It captured only serious injuries resulting in hospitals; less serious injuries amongst the study population were not captured. Thus, the costs were not comprehensive for all injuries i n this sector. This study depended heavily on the accuracy o f the diagnosis codes and dates o f both hospital and compensation database, and the matching rules used for identifying a claim matched to a hospitalization. W e acknowledge that there might be some inaccuracies i n the  linking  methodology to extract the right claims for the hospitalization cases resulting i n mismatches. Cost information was available up to 2005, which provided 7 years to develop costs for all the injury events as the last injury captured i n our study was i n 1998. However, it is likely that major costs were developed within the first 7 years after an injury event. Research on the cost o f workplace injury plays an important role i n many aspects o f industrial hygiene initiatives. K n o w i n g all the associated costs and the causes and nature o f costly injuries w i l l be helpful to employers, compensation officials and other stakeholders to identify vulnerable job groups and work processes. This information can be used to design and implement targeted preventive measures within an industry. If injuries among employed persons are not appropriately compensated, policy and prevention decisions may not be based on accurate or complete evidence or relative importance o f causes and nature o f injury, and the cost of some work-related injuries w i l l continue to be paid by other segments o f the social safety net. For  example, the burden o f uncompensated  wage-losses may be borne by the  federal  unemployment insurance system or the employee and their family and the healthcare costs were likely covered by the provincial health care system.  108  109  T A B L E 5.1: COSTS* FOR A L L (173) W O R K - R E L A T E D INJURIES REQUIRING HOSPITALIZATION A M O N G ACTIVE SAWMILL WORKERS Median cost (Range) Claim type(nuTrrbei^___ 4,377 Healthcare [493-96,920] Short-term Disability Long-term Disability Vocational rehabilitation Total  13,254 [204-142,380] 34,203 [1,754-721,790] 10,732 [39-83,357] 19,506 [493-919,726]  Total cost (% of total) 1,764,137 (15%) 3,490,051 (29%) 6,506,373 (54%) 377,690 (3%) 12,138,252  *A11 costs in 1995 constant Canadian dollar and costs imputed for 37 hospitalizations not linked to a claim  110  T A B L E 5.2: COSTS* BY CAUSE AND NATURE OF INJURY FOR 173 WORKRELATED INJURIES AMONG ACTIVE SAWMILL WORKERS Median Nonhealthcare costs [rangel  Median healthcare costs [rangej  Total Nonhealthcare costs  Total healthcare costs  (%)  (%)  Cause of Injury (Number)  Fire, Flame, Natural & Environmental (7) Struck by falling object (13) Machinery related (49) Cutting & piercing (9) Caught in or between (9) Falls (30) Struck against (24) Overexertion (16) Other cause of injury** (16) Total (173)  189,768 [2,332-458,024] 32,398 [0-822,806] 26,480 [0-372,567] 24,706 [5,116-354,008] 24,130 [6,793-667,183] 19,978 [810-411,727] 12,667 [0-352,351] 7,801 [0-68,7701 7,801 [487-204,9251 16,559  33,276 [1,819-77,737] 8,625 [543-96,920] 6,643 [493-60,923] 9,450 [1,024-69,405] 4,389 [538-26,163] 5,185 [686-48,345] 5,741 [527-33,276] 2,710 [1,031-28,145] 2,710 [569-44,208] 4,377  1,205,313 [11.62] 1,422,771 [13.71] 2,667,333 [25.71] 797,005 [7.68] 1,015,909 [9.79] 1,510,234 [14.56] 1,066,883 [10.28] 167,791 [1.62] 520,876 [5.02] 10,374,115  222,439 [12.60] 193,232 [10.95] 494,666 [28.04] 151,655 [8.59] 78,421 [4.44] 248,963 [14.11] 208,781 [11.83] 65,746 [3.72] 100,234 [5.68] 1,764,137  51,517 [0-354,008] 48,023 [2,332-458,024] 39,713 [4,205-372,567] 22,439 [8,682-208,266] 9,200 [0-822,806] 7,801 [0-166,564] 4,203 [0-112,845] 4,790 [0-189,768]  9,967 [849-60,923] 5,954 [1,819-77,737] 8,277 [538-53,475] 5,794 [1,617-29,644] 5,534 [527-96,920] 2,710 [686-28,145] 2,644 [695-35,886] 2,270 [493-33,276]  2,713,382 [26.15] 1,270,825 [12.24] 1,639,447 [15.80] 1,198,338 [11.55] 2,365,076 [22.79] 464,752 [4.47] 318,624 [3.07] 403,670 [3.89]  399,815 [22.66] 241,144 [13.66] 290,442 [16.46] 207,397 [11.75] 332,780 [18.86] 120,957 [6.85] 94,599 [5.36] 77,003 [4.36]  16,559  4,377  10,374,115  1,764,137  Nature of Injury (Number)  Open wounds(35) Burns (9) Fracture-upper limb (27) Fracture- lower limb (23) Fracture of Head & trunk (23) Dislocation, sprains, strains (35) Superficial & crushing injury(12) Other nature of Injury*** (9) Total (173)  A l l costs in 1995 constant Canadian dollar ** Other cause o f injury includes transportation, drowning, suffocation, foreign body; explosion, firearms, hot substances, electricity; other and unspecified *** Other nature o f Injury includes Internal injury-chest, abdomen, pelvis, injuries to nerves & spinal cord; traumatic complications, non-medicinal substances, unspecified, others  111  FIGURE 5.1: C L A I M O U T C O M E * CATEGORIES BY CAUSE AND NATURE OF WORK-RELATED INJURY  fr 3  E O  o E  • Healthcare  •Short-term Disability  • Long-term Disability  "Vocational Rehabilitation  50 -m•, 45 40 35 30 i 25 20 15 10  MM  5 0  «0  y y  *  Cause and Nature of Work-related Injury  *For 136 work-related injuries requiring hospitalization  112  F I G U R E 5.2 C O S T S * A N D C O M P E N S A T I O N B Y T H E W O R K E R S ' C O M P E N S A T I O N SYSTEM  14 • Compensation costs covered  • Estimated compensation costs not covered  12  $1.08  c re ro 8 c re O C 6  $0.45 $11.06 $0.42 $6.06 $0.20 $3.07  $0.38  $1.56 Healthcare  Short-term Disability  Long-term Disability  Vocational rehabilitation  Total  113  5.5 REFERENCES Alamgir H , Koehoorn M , Ostry, Tompa E . 2006-A. A n Evaluation o f Hospital Discharge Records as a tool for serious work-related Injury surveillance. Occup Environ M e d 63:290-6.  Alamgir H , Koehoorn M , Ostry A , Tompa E . 2006-B. H o w many work-related injuries requiring hospitalization in British Columbia are claimed for workers' compensation? A m J Ind M e d A m J Ind M e d 49:443-451  B C Ministry o f Health. 2005. Medical Services Plan, Quick Facts 2003/2004. http://www.healthservices.gov.bc.ca/msp/quickfacts.html. Accessed October 02, 2005.  C H S P R . 2004. Centre for Health Services & Policy Research, B C Linked Health Database. http://www.chspr.ubc.ca/hidu/. Accessed October 02, 2004.  Chamberlayne R, Green B , Barer M L , Hertzman C , Lawrence W J , Sheps S B . 1998. Creating a population-based linked health database: a new resource for health services research. Can J Public Health 89:270-3.  Drummond M F , Mark J. Sculpher M J , George W . Torrance G W , O ' B r i e n B J , Stoddart GL.1997. Methods for the Economic Evaluation o f Health Care Programmes (Third Edition). Oxford; N e w Y o r k : Oxford University Press. P 39-70.  Eastridge B J , Shafi S, M i n e i JP, Culica D , M c C o n n e l C , Gentilello L . 2006. Economic Impact o f Motorcycle Helmets: F r o m Impact to Discharge. J Trauma 60:978-984.  Hertzman C , Teschke K , Ostry A , Hershler R, Dimich-Ward H , K e l l y S, Spinelli JJ, Gallagher R P , M c B r i d e M , Marion S A . 1997. Mortality and cancer incidence among sawmill workers exposed to chlorophenate wood preservatives. A m J Public Health 87:71-9.  114  Koopmanschap M A . 1998. Cost-of-illness studies. Useful for health policy? Pharmacoeconomics 14:143-8.  Leigh JP, Cone J E , Harrison R. 2001. Costs o f occupational injuries and illnesses in California. Prev M e d 32:393-406.  Leigh JP, Waehrer G , M i l l e r T R , Keenan C . 2004. Costs o f occupational injury and illness across industries. Scand J W o r k Environ Health 30:199-205.  Nilsen P, Hudson D , Lindqvist K 2006. Economic analysis o f injury prevention-applying results and methodologies from cost-of-injury studies. Int J Inj Contr Saf Promot 13:7-13.  Rautiainen R H , Ohsfeldt R, Sprince N L , Donham K J , Burmeister L F , Reynolds SJ, Saarimaki P, Zwerling C . Cost o f compensated injuries and occupational diseases in agriculture i n Finland. J Agromedicine. 2005;10(3):21-9.  Shannon H S , L o w e G S . H o w many injured workers do not file claims for workers' compensation benefits? A m J Ind M e d 2002; 42: 467-73.  Singh M , Vaishya S, Gupta S, Mehta V S . 2006. Economics o f head injuries. Neurol India 54:7880.  Small T J , Sheedy J M , Grabs A J . 2006. Cost, demographics and injury profile o f adult pedestrian trauma i n inner Sydney. A N Z J Surg 76:43-7.  Sorensen S V , de Lissovoy G , Kunaprayoon D , Resnick B , Rupnow M F , Studenski S. 2006. A taxonomy and economic consequences o f nursing home falls. Drugs A g i n g 23:251-62.  115  Teschke K , Ostry A , Hertzman C , Demers P A , Barroetavena M C , Davies H W , Dimich-Ward H , Heacock H , M a r i o n S A . 1998. Opportunities for a broader understanding o f work and health: multiple uses o f an occupational cohort database. Can J Public Health 89:132-6.  Waehrer G , Leigh JP, Cassady D , M i l l e r T R . 2004. Costs o f occupational injury and illness across states. J Occup Environ M e d 46:1084-95.  Waehrer G , Leigh JP, M i l l e r T R . 2005. Costs o f occupational injury and illness within the health services sector. Int J Health Serv 35: 343-59.  W e i l D . 2001. Valuing the economic consequences o f work injury and illness: a comparison o f methods and findings. A m J Ind M e d 40:418-37.  W C B . 2005-A. Workers' Compensation Board o f B C ; Worker benefits http://www.worksafebc.com/claims/worker_benefits/default.asp Accessed October 02, 2005  W C B . 2005-B. Workers' Compensation Board o f B C ; Registering for coverage http://www.worksafebc.com/insurance/registering_for_coverage/default.asp Accessed October 02, 2005.  W B C . 2005-C. Workers' Compensation Board o f B C ; Forest Products Manufacturing; Focus Report on; Preventing Injuries to Workers http://smallbusiness.healthandsafetycentre.org/sc/resources/sawmills/focusforest.pdf Accessed October 02, 2005.  116  CHAPTER 6 HOSPITAL COSTS AND COMPENSATION OF TREATING WORK-RELATED SAWMILL INJURIES IN BRITISH COLUMBIA  5  6.1 INTRODUCTION A n average o f 164,404 work-related injuries occurred each year i n the Canadian province of British Columbia over the five-year period from 1997 to 2001 [ A W C B C , 2005]. Current predictions indicate that the incidence o f work-related injuries w i l l not decline notably over the next few years. In fact, the number o f reported injuries remained unchanged from 2002 to 2004 at 156,000 [ A W C B C , 2005]. Patients with serious work-related injury often experience long hospital stays and consume substantial amount o f medical and hospital services. The principal component o f Canada's health care system is a socialized health insurance plan that covers all citizens and residents [Health Canada, 2006]. It is publicly funded and under this system, citizens receive medically necessary preventative care and medical treatments from primary care physicians, hospitals, dental surgery and other medical services [Health Canada, 2006]. In Canada, the public hospital sector serves both the public health care system and the workers' compensation system. The latter is funded entirely b y employers but relies largely on the public health care infrastructure for services. Hospital costs associated with work-related injuries are likely to escalate in Canada due to the growing size o f the labour force and greater inflation i n the health service sector than the general economy [CIHI, 2006-A]. For example, the total hospital expenditures in Canada  The chapter is currently under review for publication i n Injury under the same title.  117  increased from $26 billion in 1997 to $35 billion i n 2002 [CIHI, 2006-A]. Though hospital costs account for a large component o f total healthcare costs incurred following a work-related injury that requires hospitalization, no previous studies in Canada have estimated inpatient costs associated with work-related acute hospitalizations from the health care system's perspective. This perspective is particularly relevant because the infrastructure o f the hospital sector in Canada is funded by the public sector and its primary client is the general public. Workers' compensation agencies across the country largely rely on this public infrastructure, but pay for the services directly, sometimes with a premium on the public fee schedule in order to receive expedited services. This different financing and payment scheme can create conflicting priorities for hospitals. Furthermore, i n some instances the public sector may subsidize the privately funded workers' compensation system when work-related injuries and illnesses go undetected by the workers' compensation system. The workers' compensation system is a provincial jurisdiction but is based on similar principles in the ten provinces and three territories across Canada- the liability o f employers for injuries in the workplace is no fault and collective funding, with employers paying into a monopoly not-for-profit insurer that is publicly regulated [ W C B - N S , 2006]. In return for guaranteed compensation, workers waive their right to sue their employer or co-workers through the tort system for any negligence that may have given rise to the workplace injury. Workers' compensation boards are entities independent o f direct government involvement and usually have equal representation from labor and industry [ W C B - N S , 2006]. If a worker is injured while on the job, the compensation system pays for accepted medical expenses (medical services and supplies) and wage-loss benefits, plus any necessary rehabilitation services.  118  Most o f the hospital cost statistics on work-related injury i n Canada have been based on reports from the workers' compensation agencies, but these agencies might not capture all workrelated injury [Shannon and Lowe, 2002; A l a m g i r et al., 2006-A]. Therefore, it is necessary to study costs using injury reports from an independent surveillance source to try to obtain a more comprehensive account o f serious injuries. Additionally, estimating costs using an independent source and comparing the findings with the results reported by the workers' compensation systems w i l l reveal the magnitude o f the hospital cost that is shifted from the compensation agency to the provincial health care system. Sawmills in British Columbia provide an important work-setting to study the hospital costs o f work-related injury as this sector is large and unionized, contributes significantly to the economy o f this province, is considered a hazardous industry, and its workers should be covered by the compensation system. A large cohort study on sawmill workers in B C , initially started i n the 1980's to investigate the risk o f cancer associated with the use o f Chlorophenol fungicides [Hertzman et al., 1997] was expanded to investigate a wide variety o f occupational health issues in the forest industry [Teschke et al., 1998]. This study analyzes data from a sub-set o f the full B C sawmill cohort, specifically, individuals who were working in the study sawmills at the time o f hospital admission. The primary objective o f this study was to assess the hospital costs associated with workrelated injuries o f individuals in the B C sawmill cohort that were incurred by the B C hospitals during 1989-1998. Additionally, it estimated the hospital costs o f the subset o f work-related injury not compensated by the provincial workers' compensation system and explore the range o f costs for different types o f injuries. This latter information provides insight into the most  119  expensive injuries and can be used to gauge where prevention efforts might have the greatest payback. Hospital discharge records in the Canadian province o f British Columbia ( B C ) have the potential to be a useful resource for estimating the costs associated with treating work-related injuries reaching hospitals. Almost all eligible residents o f B C (over 4.1 million people) are enrolled with the provincial Medical Services Plan - M S P [ B C Ministry o f Health, 2005]. The M S P processes claims for insured services submitted by physicians, supplementary health care practitioners, hospitals, laboratory services and diagnostic procedures [ B C Ministry o f Health, 2005]. Hospital discharge data is a potential source o f information on serious work-related injuries. External cause o f injury codes and source o f payment information are available in hospital discharge records to identify work-relatedness o f hospitalization cases i n British Columbia ( B C ) , Canada [ICD-9; Alamgir et al., 2006-B]. Since A p r i l 1989, hospitals i n B C have coded an additional digit to the International Classifications o f Disease diagnosis coding schedule. This additional information enhanced the utility o f discharge data as a work related injury surveillance system [Alamgir et al., 2006-B].  6.2 METHODS There is no definitive method for calculating costs o f hospital stays in Canada, as there are no provincial case-costing systems in place. One popular method has been the use o f a cost per weighted case or Cost per Resource Intensity Weight (RIW) methodology utilizing financial and statistical reporting from hospitals and health authorities according to the Canadian Institute for Health Information National Management Information Systems guidelines [CIHI, 2006-B]. A  120  net total inpatient cost is arrived at and the total acute care RIWs are used as a denominator to determine an average cost per weighted case. Another approach for calculating hospitalization costs is the use of the Standard Ward Rate (SWR), sometimes referred to as a Per Diem Rate. This is the daily charge for hospital stays for Inter-provincial and workers' compensation billing purposes [BC Ministry of Health Services]. For example, when a resident from Alberta is hospitalized in a B C hospital for 3 days, an SWR for the hospital is multiplied by 3 and a bill is submitted for the stay. This rate is generally re-estimated on a yearly basis and is also site-specific. This rate has been compared to the "rack rate" of a hotel and does not take into account the cost of overhead. The same daily rate is used for all cases such that one-day for one type of patient is the same as that of another type of patient in a particular hospital. Any differences in costs between patients would be due to different lengths of stay. Although the use of a standard ward rate is a cruder method for calculating hospital costs, hospitals in B C currently use it to calculate charges to the provincial workers' compensation agency for work-related injuries [BC Ministry of Health Services]. Therefore, the method is more appropriate to assess costs of injury categories from the payer's perspective. When the compensation agency is not capturing or compensating a hospital for an injury-related stay, it is at this rate that the costs to the hospital are forgone. Hospital discharge records and workers' compensation claims for this study population were obtained from the British Columbia Linked Health Database (BCLHD). The B C L H D is a health data resource for research purposes created and maintained by the University of British Columbia's Centre for Health Services and Policy Research. It contains datasets with information on physician visits, hospital discharges, deaths, births, as well as extended care, drug  121  usage, and workers' compensation claims since 1985 [ C H S P R , 2005-A]. The datasets are linked to a central registry file o f all persons in the province covered by the B C Medical Services Plan ( M S P ) [Chamberlayne et al., 1998]. The hospitals have a year-specific standard billing schedule prepared by the provincial Ministry o f Health by which they b i l l and collect payment from agencies such as the Workers' Compensation Board o f British Columbia ( W C B ) . The hospital discharge dataset provided for research purposes by the B C L H D is a file o f separations (discharges, transfers, and deaths) o f in-patients and day surgery patients from acute care hospitals in B C [ C H S P R , 2005-B]. Thus, outpatient cases such as emergency room only visit in which patients are not admitted to the hospital, are excluded from the research database. Records with the same admission and separation date are generally coded as D a y Care Surgery (DCS). The D C S rate for that year from the Ministry's billing data was applied for costing purposes. For records with the same admission and separation date that were not coded as D C S , the full day's rate for that hospital for that year was applied. Some cases were transferred to other hospitals on the same day o f admission. For these cases, it was assumed that they stayed more than 6 hours in the first hospital, and so a full day's rate for that hospital was included in the cost calculations. A s part o f previous investigations, a total o f 5, 876 members were linked with their health records (using the B C L H D as o f A p r i l 1989) from the original cohort o f 6,512 members actively employed on or after A p r i l 01, 1989. Work-related injuries were also captured among these sawmill workers using the  hospital discharge  dataset  [Alamgir  et  al., 2006-B].  Hospitalization records were identified as work-related using I C D - 9 external cause o f injury codes that indicate place o f occurrence; and the responsibility o f payment schedule, which  122  identifies workers' compensation as being responsible for payment. The methods are described by Alamgir et al [2006-B]. The principal diagnosis for the patient's stay in a hospital was used to designate the nature of injury and each hospitalization record was then categorized into meaningful broad nature of injury categories (Table 6.1). External cause of injury (ICD-9 E codes) was used to designate the cause of injury and each hospitalization record was then categorized into meaningful broad cause of injury categories (Table 6.2). The workers' compensation claim records for this study population were extracted from 1989 to 1998, and matched with the hospitalized work-related injury records using the admission and separation dates and ICD-9 codes of the hospital discharge records with the injury date and ICD-9 codes of the compensation claim records [Alamgir et al., 2006-A]. Costs were calculated from the hospital's perspective. All costs were expressed in 1995 constant Canadian dollars using the provincial medical consumer price index [Drummond et al., 1997]. A 5% discounting rate was applied to adjust for the time value of money [Drummond et al., 1997]. Total costs and median costs were calculated by cause and nature of injury. Costs were also calculated for the subset of work-related hospitalizations that the hospital did not appear to be reimbursed for by the workers' compensation system.  6.3 RESULTS  For the 5,876 sawmill workers there were a total of 370 hospitalization events captured. By either of the two indicators (E Codes or payment schedules), 173 (47%) records were identified as work-related [Alamgir et al., 2006-B]. Of these 173 records, 136 (79%) were matched to compensation claims. Thus, 37 (21%) of the work-related injuries could not be  123  matched with a workers' compensation claim record. The study population for the 173 injuries was predominantly male (only 3 were females) and white (90%). The median age o f the injured workers was 41 years. Nineteen percent o f hospitalizations were coded as day care surgery, and 85% o f records were coded as either urgent or emergency cases. Table 6.1 describes the median length o f stay by nature and cause o f injury. Burns had the longest stays in hospitals and dislocation, sprains and strains had the shortest stays. In terms o f cause o f injury, fire, flame, natural & environmental had a median stay o f 18 days, whereas, cutting and piercing had only a median stay o f 1 day in hospital. Table 6.2 presents the median, mean and total hospital costs o f work-related injury requiring hospitalization among the study population. The median cost was highest for injuries involving fire, flame,  natural & environmental  and lowest for injuries involving cutting &  piercing. In terms o f nature o f injury, burns were the most costly injury category and dislocation, sprains & strains were the least costly. In terms o f total costs, the cause o f injury category o f fire, flame, natural & environmental,  machinery related and falls were the most costly. For  nature o f injury, burns, fracture of upper limb and fracture of head & trunk were the most costly categories. The total hospital cost for the 173 studied injuries was $434,990. Out o f a total hospital cost o f $434,990 for the 173 work-related injuries, the provincial compensation agency apparently did not compensate $50,663 (12%) (Figure 6.1).  6.4 DISCUSSIONS  According to the study findings, the median hospital cost for treating a work-related injury was $847 with a range o f $144 to $45,409. The median stay was 3 days with the shortest being 1 day and the longest being 51 days. These figures highlight the expenses incurred by the  124  hospitals for the treatment o f acute work-related injuries, much o f which results from the length o f hospital stay. There was a large variance o f median hospital costs for the injury categories studied. Injuries involving fire, flame,  natural & environmental;  struck against and struck by falling  object were the most costly causes o f injury. Injuries involving burns, fracture of lower limb and fracture  of head & trunk were the most costly nature o f injuries. In terms o f total costs, fire,  flame, natural & environmental; head & trunk and fracture  machinery related and falls by cause and burns, fracture  of  of upper limb by nature were the most costly injuries. Targeted  interventions designed to reduce these injuries w i l l save substantial healthcare resources. For example, reducing one burn injury would save on average o f $10,000 to $15,000 in hospital costs alone. Literature on costs o f injury related stays in hospitals is rare. Polinder and colleagues [2005] estimated costs o f injury-related hospital admissions i n 10 European countries. Highest costs were found for hip fractures [E5,530], fractures o f the knee/lower leg [E3,504], burns [E4,065] and skull-brain injury [E2822]. The highest cost per patient for admitted injury patients and the corresponding mean length o f stay (days) were E3,242 and 6.9 for Austria, E2,954 and 8.4 for Netherlands, E2,819 and 5 for Norway, and E2,771 and 9.3 for Spain and E2,745 and 6.1 for Denmark. Reducing the duration o f hospital stays is one potential way o f minimizing expenditure to the hospitals following work-related injury. In many hospitals, patients experience delays for surgery; which leads to inefficient use o f bed capacity, increased nursing dependency and longer hospital stays. The stipulation o f adequate resources to minimize surgical delays would benefit patients and reduce expenditures. Moreover, the majority o f hospital days are spent recuperating  125  after surgery and the introduction o f programs to limit inpatient stay and improve rehabilitation have been shown to be cost-effective without adversely impacting health outcomes [SanchezSotelo et el., 2006; Stubbs et al., 2005]. Reducing inpatient stay would also free hospital beds for other populations, and could eventually lead to reduced expenditures to the hospitals without adversely affecting the health o f the B C population. M i n i m i z i n g direct hospital costs may also lessen the financial burden related to workrelated injury. However, it may be more effective to tackle the root o f the problem by reducing the occurrence o f work-related injury. Evidence based strategies to reduce the number o f workrelated injury should therefore be targeted. Our findings from this study suggest that 12 % o f work-related injury hospital costs do not appear to be covered by the workers' compensation authority. These costs are attributable to approximately 20% o f the work-related hospitalized injuries. These findings suggest that substantial costs are being transferred to the provincial health care system. Further research is necessary to identify the circumstances surrounding the diversion o f these costs from the workers' compensation system to the public health care sector. The strength o f this study was the use o f a detailed and accurate collation o f billing charts from which costs were derived. W e have accounted for each patient-day and the billing rate was year and hospital specific.  This study takes  advantage  o f readily available and large  administrative datasets. Other Canadian studies [Dimich-Ward et al., 2004; Locker et al., 2002] have also examined the use o f administrative datasets for research purposes and the reliability and validity o f such records have been established in other places [Beghi et al., 2001; Kashner, 1998; Vestberg et al., 1997; V i r n i g and M c B e a n , 2001; Rawson and M a l c o l m , 1995]. W e used  126  Consumer Price Index for healthcare in British Columbia to take care o f the inflation. Additionally, a 5% discount rate was used to adjust for the time value o f money. Several limitations should be considered when interpreting the results o f this study. First, the study depended heavily on the accuracy o f the diagnosis codes and dates o f both hospital and compensation databases. Second, there might have been weakness i n the linking methodology to extract the right compensation claims for the hospitalization cases because the date window and injury coding might have linked different injury events. Finally, the method o f using daily charge for hospital stays has its limitations. For example, it does not include overhead costs and it considered all injuries consumed similar amounts o f resources per day. However, when exploring the billing relationship between the hospitals and the compensation agency, it is appropriate. The current hospital costing methods remain inaccurate and imperfect, making precise financial evaluations inherently difficult. A n assumption for this study was that the bills hospitals submitted to the compensation agency were all eventually paid for by the agency. Future cost studies could improve upon the analyses undertaken i n this study by incorporating differential resource consumption patterns by injury cases within each hospital.  127  T A B L E 6.1: MEDIAN STAY IN HOSPITAL BY CAUSE AND NATURE OF INJURY (N=173) HOSPITALIZATIONS FOR WORK-RELATED INJURIES AMONG A SAWMILL COHORT N  Median  Minimum  Maximum  7  18  3  51  30 13 24 16 9 49 9 16 173 N 9 23 23 12 27 35 35 9 173  3 3 3 2.5 2 2 1 2.5 3 Median 13 4 3 3 2 2 1 4 3  1 1 1 1 1 1 1 1 1 Minimum 2 1 1 1 1 1 1 2 1  30 13 14 7 13 21 8 13 51 Maximum 51 12 14 19 30 15 7 6 51  C^u^of^mjury  Fire, Flame, Natural & Environmental Falls Struck by falling object Struck against Overexertion Caught in or between Machinery related Cutting and piercing Other injuries* Total Nature of Injury  Burns Fracture of lower limb Fracture of skull, intracranium, spine & trunk Superficial injury & crushing Fracture of upper limb Open wounds Dislocation, Sprains & Strains Other Injuries** Total  * Other sources o f injury include transportation; drowning, suffocation, foreign body; explosion, firearms, hot substances & electricity; others and unspecified ** Other nature o f injury includes internal injury of chest, abdomen, pelvis; injuries to nerves & spinal cord; traumatic complications; non-medicinal substances, unspecified, others  128  T A B L E 6.2: COSTS* OF HOSPITALIZATION BY CAUSE AND NATURE OF INJURY (N=173) HOSPITALIZATIONS FOR WORK-RELATED INJURIES AMONG A SAWMILL N  —  Median [MinimumMaximum]  Mean (Std. Deviation)  Total  Cause of Injury  7  16,524(15,960)  10,575 [2,270-45,409]  115,673  30 13 49 24 9 16 9 16  2,370 (4,539) 2,130(3,254) 2,034 (3,335) 1,624(1,989) 1,287(1,604) 996 (850) 705 (1,010) 2,998 (7,186)  857 [144-24,082] 1,093 [372-12,551] 813 [144-18,164] 1,206 [262-9,6301 423 [262-5,2501 690 [257-2,606] 296 [272-3,368] 774 [239-29,584]  71,102 27,692 99,680 38,987 11,587 15,945 6,352 47,972  9  15,960 (15,873)  10,575 [423-45,409]  143,639  23 27 23 12 35 35  2,704 (3,522) 2,342 (5,520) 2,180(1,461) 1,999 (2,664) 1,453 (2,1710 833 (850)  991 [372-12,551] 684 [239-24,082] 1,800 [251-6,084] 899 [406-8,029] 449 [262-11,400] 437 [144-3,675]  62,184 63,222 50,149 23,989 50,872 29,163  9 173  1,308 (923) 2,514 (5,489)  1,447 [406-2,801] 847 [144-45,409]  11,773 434,990  Fire, Flame, Natural, Environmental Falls Struck by falling object Machinery related Struck against Caught in or between Overexertion Cutting and piercing Other causes of injury Nature of Injury Burns  Fracture of head & trunk Fracture of upper limb Fracture of lower limb Superficial injury & crushing Open wounds Dislocation, sprains & strains  Other nature of Injury Total  * In 1995 Canadian Dollar  129  FIGURE 6.1: COMPENSATION OF HOSPITAL COSTS* BY T H E WORKERS' COMPENSATION AGENCY (N=173 HOSPITALIZATIONS) FOR WORK-RELATED INJURIES AMONG A SAWMILL COHORT)  $50,663 12%  $384,327 88%  • W C B uncompensated (37)  • W C B compensated (136)  * In 1995 Canadian Dollar  130  6.5 R E F E R E N C E S  Alamgir H , Koehoorn M , Ostry A , Tompa E , Demers P. 2006-A. H o w many work-related injuries requiring hospitalization i n British Columbia are claimed for workers' compensation? A m J Ind M e d (In press) Alamgir H , Koehoorn M,Ostry A , Tompa E , Demers P. 2006-B. A n Evaluation o f Hospital Discharge Records as a T o o l for Serious Work-related Injury Surveillance. Occup Environ M e d 63: 293-296. A W C B C , 2005. Association o f Workers' Compensation Boards o f Canada. Workers' Compensation Board/Commission Financial and Statistical Data http://www.awcbc.org/english/board_data.asp  Accessed January 25, 2005  Beghi E , Logroscino G , M i c h e l i A , M i l l u l A , Perini M , R i v a R , Salmoiraghi F, Vitelli E ; Italian A L S Registry Study Group. 2001. Validity o f hospital discharge diagnoses for the assessment o f the prevalence and incidence o f amyotrophic lateral sclerosis. Amyotroph Lateral Scler Other Motor Neuron Disord 2:99-104 B C Ministry o f Health. 2005. Medical Services Plan, Quick Facts 2003/2004. Available at http://www.healthservices.gov.bc.ca/msp/quickfacts.html.  Accessed October 02, 2005.  B C Ministry o f Health Services. Office o f the Assistant Deputy Minister. Financial and Corporate Services. Standard Ward Rate. Years 1989-1998 C I H I , 2006-A. The Canadian Institute for Health Information. National Health Expenditure Trends, 1975-2005; http://secure.cihi.ca/cihiweb/dispPage.jsp?cw_page=PG_404_E&cw_topic=404&cw_rel=AR_3 1_E. Accessed January 25, 2006 C I H I , 2006-B. Canadian Institute o f Health Information. Resource Intensity Weights http://secure.cihi.ca/cihiweb/dispPage.jsp?cw_page=casemix_riw_e Accessed October 02, 2005.  131  C H S P R . 2005-A. Centre for Health Services & Policy Research, B C Linked Health Database; http://www.chspr.ubc.ca/hidu/. Accessed October 02, 2005. C H S P R . 2005-B. Centre for Health Services & Policy Research, Hospital Separations File. http://www.chspr.ubc.ca/files/data/tables/hosp.htm  . Accessed October 02, 2005.  Chamberlayne R, Green B , Barer M L , Hertzman C , Lawrence W J , Sheps S B . 1998. Creating a population-based linked health database: a new resource for health services research. Can J Public Health. 1998;89:270-3.  Dimich-Ward H , Guernsey JR, Pickett W , Rennie D , Hartling L , Brison R J . 2004. Gender differences in the occurrence o f farm related injuries. Occup Environ M e d 61:52-6. Drummond M F , Sculpher M J , Torrance G W , O ' B r i e n B J , and Stoddart G L . Methods for the Economic Evaluation o f Health Care Programmes (Third Edition). Oxford University Press. P39-70 Health Canada.2006. Health Care System, http://www.hc-sc.gc.ca/hcs-sss/index_e.html Accessed January 25, 2006  Hertzman C , Teschke K , Ostry A , Hershler R, Dimich-Ward H , K e l l y S, Spinelli JJ, Gallagher R P , M c B r i d e M , M a r i o n S A . 1997. Mortality and cancer incidence among sawmill workers exposed to chlorophenate wood preservatives. A m J Public Health 87:71-79. I C D - 9 . 1989. International Classification o f Diseases, Ninth Revision, Clinical Modification. U S Department o f Health and Human Services. ( I C D - 9 - C M ) Hyattsville, M D . Kashner T M . 1998. Agreement between administrative files and written medical records: a case o f the Department o f Veterans Affairs. M e d Care 36:1324-36. Locker A R , Pickett W , Hartling L , Dorland J L . 2002. Agricultural machinery injuries i n Ontario, 1985-1996: a comparison o f males and females. J Agric Saf Health 8:215-23.  132  Rawson N S , M a l c o l m E . 1995. Validity o f the recording o f ischaemic heart disease and chronic obstructive pulmonary disease i n the Saskatchewan health care datafiles. Stat M e d 14:2627-43.  Sanchez-Sotelo J, Haidukewych G J , Boberg CJ.2006. Hospital cost o f dislocation after primary total hip arthroplasty. J Bone Joint Surg A m 88:290-4. Shannon H S , Lowe G S . 2002. H o w many injured workers do not file claims for workers' compensation benefits? A m J Ind M e d 42:467-73. Stubbs G , Pryke S E , Tewari S, Rogers J, Crowe B , Bridgfoot L , Smith N . 2005. Safety and cost benefits o f bilateral total knee replacement in an acute hospital. A N Z J Surg 75:739-46. Teschke K , Ostry A , Hertzman C , et al. 1998. Opportunities for a broader understanding o f work and health: Multiple uses o f an occupational cohort database. Can J Public Health 89:132-136.  Vestberg K , Thulstrup A M , Sorensen H T , Ottesen P, Sabroe S, Vilstrup H . 1997. Data quality o f administratively collected hospital discharge data for liver cirrhosis epidemiology. J M e d Syst 21:11-20  V i r n i g B A , M c B e a n M . 2001. Administrative data for public health surveillance and planning. A n n u Rev Public Health 22:213-30.  W C B - N S , 2006. Workers' Compensation Board o f N o v a Scotia. Meredith principles. http://www.wcb.ns.ca/policymanual/meredith.html Accessed January 25, 2006  133  CHAPTER 7 EPIDEMIOLOGY OF WORK-RELATED INJURIES REQUIRING HOSPITALIZATION AMONG SAWMILL WORKERS IN BRITISH COLUMBIA, 1989-1998  6  7.1 INTRODUCTION Sawmills are a major source o f economic activity and employment in many countries including the United States o f America ( U S A ) , Canada, China, Malaysia, Brazil, Indonesia, France, Sweden and Germany [Demers and Teschke, 1998]. About 1% o f the entire global workforce is employed in a wood products industry [Demers and Teschke, 1998]. In British Columbia ( B C ) , a province o f Canada, about 2% o f the workforce was working in the logging and forestry industry during 1993-1998 [ B C Statistics, 2004]. Sawmills are hazardous work environments because o f the nature o f the work processes, the types o f machines and tools used, and materials handled [Demers and Teschke, 1998]. A s a result, sawmill workers are at a higher than average risk o f sustaining work-related injuries. From 1993 to 1997, the average accepted, time-loss claim rate was 7 injuries per 100 full-time equivalent workers in B C sawmills compared to the overall provincial average o f 5.4 injuries [ W C B , 1999]. Epidemiologic study o f work-related injuries has been hindered by the lack o f a complete, independent, standardized, reliable, elaborate, and consistent reporting system. A m o n g the information sources available for studying work-related injury, workers'  compensation  systems are currently considered a major surveillance tool. However, some studies in U S A  6  The chapter is currently under review for publication in The European Journal of  Epidemiology  under the same title.  134  [Waller et a l , 1989; Frumkin et al., 1995; Stanbury et al., 1995; Biddle et al., 1998; Rosenman et al., 2000] and Canada [Shannon and Lowe, 2002; Alamgir et al, 2006-A] have explored underreporting o f work-related injuries by the workers' compensation systems. This has led to an interest in identifying different and independent sources o f information for use in work-related injury surveillance. In Canada, hospital discharge records represent a readily accessible and customarily collected source o f data for the monitoring o f severe non-fatal injuries. It has  detailed  information on the nature, cause, and severity o f injury related admissions, and has followed the standard International  Classifications o f Disease diagnosis coding schedule [CIHI, 2004].  Because o f the public health care system in Canada and the all-inclusive coverage  of  hospitalizations, hospital discharge records have the prospect to be a handy data resource for severe injury surveillance. Individual admissions can be identified as work-related using ICD-9 external cause o f injury codes that can specify place o f occurrence responsibility o f payment  [ICD-9]; and  schedule, which can identify workers' compensation  the  as being  responsible for payment. In Canada, the potential o f hospital discharge records to capture workrelated injury has been recently validated [Alamgir et al., 2006-B] and a limited number o f other investigations have also attempted earlier to capture work-related events using hospital discharge records [Dimich-Ward et al., 2004; Locker et al., 2002; Liss et al., 2000]. The purposes o f this investigation were to describe work-related injuries requiring hospitalization from 1989 to 1998 by cause, nature, and body parts among a cohort o f the sawmill workers i n British Columbia and identify the job categories that were at higher risk o f sustaining wok-related injury.  135  7.2 M E T H O D S A N D D A T A S O U R C E S A large cohort study was composed o f sawmill workers i n B C in the 1980's to investigate the risk o f cancer associated with the use o f Chlorophenol fungicides and it was later expanded to investigate other occupational health issues in the forest industry [Hertzman et al., 1997; Teschke et al., 1998]. A s part o f previous investigations, a total o f 5,876 cohort members were linked with their health records using the British Columbia Linked Health Database ( B C L H D ) as o f A p r i l 1989 from the original cohort o f 6,512 members, who were employed i n sawmills on or after A p r i l 1989 (90% linkage rate). The cohort was followed from A p r i l 1989 to December 1998 for any potentially workrelated hospital admission. The study populations were followed up from A p r i l 1989 for hospital admission to study end date (December 1998), date o f death, or date o f last employment, whichever occurred earlier. Hospital discharge records for this study population were obtained from the B C L H D [ C H S P R , 2005]. The B C L H D is a health data resource for research purposes created and maintained by the University o f British Columbia's Centre for Health Services and Policy Research ( C H S P R ) . It contains datasets recording physician visits, hospital discharges, deaths, births, as well as extended care, drug usage, and workers' compensation claims since 1985 [ C H S P R , 2005]. The datasets are linked to a central registry file o f all persons in the province covered by the B C Medical Services Plan ( M S P ) , [Chamberalayne, 1998] representing almost all residents o f British Columbia (over 4.1 m i l l i o n people). Hospital discharge records were extracted for an injury diagnosis between A p r i l 1989 and December 1998, and were identified as work-related using the I C D - 9 external cause o f injury codes and the responsibility o f payment schedule. The methods are described in more detail by  136  Alamgir et al [2006].  Individual admissions were identified as work-related using ICD-9  external cause o f injury codes that indicate place o f occurrence [ICD-9, 1989]; and the responsibility o f payment schedule, which identifies workers' compensation as being responsible for payment. Since A p r i l 1989, the hospitals i n B C started coding an additional digit to the I C D 9 diagnosis schedule that enhanced its utility as a work-related injury surveillance system [Aamgir et al., 2006-B; ICD-9]. Information on the cohort members include sex, race, and birth date; and work history records include information on m i l l , job category, and start and end o f each job at sawmills. Jobs in the B C Sawmill Cohort study were categorized by skill level according to a classification system developed by others for a case-control study o f sawmill injuries i n Maine [Punnett, 1994]. Jobs were classified by the level o f skill required as 1) foreman/supervisor, 2) skilled trades, 3) material handler/unskilled, 4) machine operator/attendant/clearer/sorter,  5) mobile  equipment operator, 6) inspector/grader, 7) non-wood production and others. Each record in the hospital discharge database was first identified as work-related or not. The injuries were described by the nature o f injury using the ICD-9 primary diagnosis codes, cause o f injury using the ICD-9 external cause codes, and then by body parts also identified through the I C D - 9 primary diagnosis codes. For example, an I C D - 9 code o f 801 is a fracture o f base o f skull. The nature o f injury is fracture o f head and trunk, and the body part is head. A n I C D - 9 code o f E888 is an unspecified fall - a cause o f injury. The cause, nature and the body parts were then categorised into related, broader groups. A g e o f the workers was calculated at the date o f hospital admission. From the start and end o f employment date for each sawmill job, the total person-years and person-years at each single job that were under follow-up were  137  calculated. The job of a worker while injured was also identified. The hospitalization rates for injury categories and job categories were calculated per 1,000 person years.  7.3 RESULTS Among the 5,876 sawmill workers at risk, only 131 were women and 845 were nonwhite. With 31,846 total person years of observation, there were 370 injury-related hospitalization events captured between 1989 and 1998. B y either of the two indicators (E Codes or payment schedule), 173 injury hospitalizations were identified as work-related. Of the 173 cases, only 3 occurred among females and 17 among non-white workers. The median age at time of hospitalization was 41 years [range: 19-64]. Figure 7.1 shows the distribution of work-related injury by age category. During the ten-year follow-up period, the overall injury rate for workrelated hospitalization was 5.4 per 1,000 person years. Table 7.1 and 7.2 present cross-tabulation of the nature, cause and body parts of the injuries studied. The most frequent work-related injuries by nature of injury were dislocation, sprains & strains (20%), open wounds (20%), and fracture of upper limbs (16%) (Table 7.3). Fractures, regardless of the body part, comprised 42% of all the injuries. During the study period, the most frequent causes of injury were machinery related (28%), falls (17%) and being struck against (14%). In terms of body parts, the hand & finger was associated with a third of all work-related injuries followed by the leg, knee & ankle, which made up one fourth of all injuries. B y exploring the relationship between cause of injury and body parts affected (results not shown), it was found that most of the work-related falls involved leg, knee & ankle, whereas, most struck against cases involved head, face & neck. Hands & fingers involved most of the machinery related incidents and overexertion, as anticipated, involved mainly trunk, back &  138  groin. Dislocation,  sprains & strains primarily involved leg, knee & ankle and trunk, back &  groin. When examining work-related hospitalizations by work history, very few injuries occurred among workers i n jobs such as foreman & supervisor, mobile equipment operator, or non-wood industry & non-production jobs (Table 7.4). Eighty-two percent o f the cases involved machine operators, attendants, clearers & sorters; material handling & unskilled, and skilled trades (tool users). The job groups that were at high risk o f sustaining serious injuries were skilled trades (6.91 work related hospitalizations per 1,000 per years), machine operators, attendants, clearers & sorters (5.96 per 1000 per years) and material handling & unskilled (5.52 per 1000 person years). A m o n g machine operators, attendants, clearers & sorters, the most frequent work-related cases o f injury were machinery related (31%), struck by falling  object (16%) and falls (16%)  (Table 7.5). A m o n g skilled trades (tool users) the most frequent causes were machinery related (27%) and struck against (23%). A m o n g material handling & unskilled workers machinery related  (30%)  was  also  the  most  common  cause  of  injury.  Among  machine  operators/attendants/clearers/sorters, the most frequent nature o f injuries were open wounds (22%) and fractures  of upper limb (22%). A m o n g skilled trades (tool users), and material  handling & unskilled workers, the most frequent nature o f injuries (about 20%) were open wounds and dislocation, sprains, & strains. Between 55-65% injuries among machine operators, attendants, clearers & sorters, material handling/unskilled and skilled trades (tool users) involved hand & finger and leg, knee & ankle.  139  7.4 DISCUSSIONS This study identified and described work-related injuries requiring hospitalization by cause, nature and body parts among a cohort sawmill workers in British Columbia during 19891998, and explored the relationship o f job types with injury categories. Although modern technology has greatly reduced the amount o f physical work involved i n operating sawmill machinery, among the sawmill workers in this study, the most common cause o f injury still involved machinery. Sawmill workers operate, monitor and control various machines and tools that saw timber logs into rough lumber and then saws, splits, trims and planes the coarse lumber into dressed lumber. Following safe work practices and operating machinery when all safeguards are functioning should be helpful to prevent injuries [ C D C , 2004; Trump, 1985]. Studies also show that on-the job training for work machinery also helps to reduce the risk o f injuries [ C D C , 2004; Trump and Etherton, 1985]. Falls were the second most important cause o f sawmill injuries. Previous studies o f occupational falls have identified environmental or physical factors (surfaces, shoes, lighting, etc.), organizational deficiency (inadequate signs and indicators, inadequate  maintenance  schedule, etc.), and behavioural factors (work pace, balance alteration) as risk factors for falls [Gauchard, 2001]. The hands and fingers remained the body parts at greatest risk o f getting injured among the sawmill workers. A review study by Barr and colleagues [2004] suggests that these injuries are associated with the longest absences from work and are, therefore, associated with greater lost productivity and wages than those o f other anatomical regions. According to this review, repetitive, hand-intensive movements, alone or in combination with other physical, nonphysical, and non-occupational risk factors, contribute to the development o f hand and finger injury. O n  140  the other hand, injuries o f leg, knee & ankle are less well-understood as epidemiological studies o f such injuries are scarcely available [Conti and Silverman, 2002]. In terms o f nature o f injury, open wounds and dislocation,  sprains and strains were  common categories among this study population. In this study open wounds included such injuries as cuts, lacerations, puncture wounds and traumatic amputations. The risk factors for compensated claims on sprains and strains were studied by Choi and colleagues [1996] in Ontario; they suggested a number o f work environments and activities associated with a high risk  o f occurrence o f sprains and strains, including overexertion, bodily reaction from  involuntary motions, running and stretching, and slippery surfaces. This study also identified some vulnerable job groups among sawmill workers. Machine operators, attendants, clearers & sorters, skilled trades (tools users), and material handling & unskilled employees in sawmill were found to sustain most o f the injuries that required hospitalization. Interestingly, mobile equipment operators did not experience that many injuries. A s expected, supervisor & foreman was found to be the safest job group relative to other job groups in sawmills. Common causes and vulnerable body parts inside the job groups were also identified. Some other studies previously investigated sawmill injury. Barroetavena [2001] i n an epidemiologic investigation o f injury mortality among sawmill workers i n British Columbia found the overall fatality rate to be 18.1 per 100,000 person-years for the period o f 1950-1990. Machine operators and mobile equipment operators were the occupational groups with the highest crude fatality rates. Over 80% o f the deaths were caused by severe trauma to the head, spinal cord, or multiple sites. Driscoll and colleagues [1995] reviewed the fatal injuries among the sawmill workers o f Australia. W i t h an injury rate o f 30 per 100,000, the activities at the time  141  o f the injury event were identified as working with a bench saw, loading/unloading, and traffic related. A m i n o f f [1974] analyzed sawmill injuries reported to Swedish National Social Insurance Board during 1970-1971. Maintenance workers sustained the highest frequency o f injuries followed by those working in the packaging, sawing and bundling areas. Larson [1991] reviewed sawmill claims filed with the insurance agency i n Sweden for severe injuries during 1988-1989. One third o f the injuries were associated with some type o f contact with machines (mostly sawing machines and conveyors). In a study on Maine sawmill workers, Cooke and Blummenstock [1979] abstracted data from employer's reports o f injuries filed with the Workers' Compensation Commission during 1972. The results showed that younger (less than 24 years) and older (more than 45 years) workers and those with temporary assignment had more severe injuries. Punnet [1994] in a casecontrol study examined the relationship between environmental risk factors and work-related acute traumatic injuries among sawmill workers also in Maine. The distinctive working conditions that prevailed on injured workers were jobs in machine-paced workstations, exposure to dangerous work methods and materials, loud noise levels, fast work pace, high lifting demands, and frequent postural stress. Laflamme and Cloutier (1988) investigated the typical scenarios where injuries occur most often i n Sweden. Most injuries occurred in the sawing section while workers were handling logs/planks. Regarding the types o f machines involved, accidents occurred more frequently at the sawing and conveying machines. A study by Bode and colleagues [2001] found lacerations as the most common injury among the factory floors i n a Nigeria sawmill. They also found the upper limbs to be involved i n  142  66% o f the injury cases and the highest injury rate occurred among the machine operators. In another study by Burridge and colleagues [1997], who studied work-related hand and lower-arm injuries i n N e w Zealand sawmill workers between  1979 and 1988, piercing and cutting  instruments and machinery were reported to be the two most common agents o f work-related hand and lower-arm injury. A few other studies have investigated hospitalized work-related injuries in different study populations and industrial sectors. Layne and Landen [1997] studied work-related injuries to workers 55 years o f age and older presented for treatment in hospital emergency departments across the United States during 1993; the types o f injuries most  frequently  requiring  hospitalization were fractures or dislocations that resulted from a fall. Husberg and colleagues [2005] used The Alaska Trauma Registry which is an injury surveillance tool focused on hospitalized nonfatal injuries i n the Alaskan construction industry. During 1991-1999, the average annual injury rate was 0.39 injuries/100 workers and the leading causes o f injury included falls (48%) and machinery (15%). Physical workload and work processes have been consistently rated as high risk factors for work-related injuries. However, non-standardization o f job classification makes it hard to compare findings across studies. While there is similarity o f the key findings found in this study with the other studies cited here, different injury surveillance systems make it hard to compare injury rates and statistics across studies, industries, occupations and countries. Comparing injury statistics across industries and surveillance systems is also hard because o f the varying tasks done by the workers, differences in safety regulations i n jurisdictions, differences in coding and reporting requirements, and differences in outcome definitions (e.g. severity o f injuries). Some studies  143  report injuries only by nature, some by cause, whereas others by the body parts. Almost no studies were found to report injuries by all-nature, cause and body parts. Some studies described injuries by amalgamating nature and cause. However, a "struck against" injury does not provide an indication o f the body part nor does it tell what the nature o f the injury was. Identifying the affected body parts reveals the vulnerability o f the body parts o f the workers that need safeguarding. Contrary to most available literature on work-related injury, this study described injuries by cause, nature and body parts involved using standard I C D - 9 diagnosis codes. U s i n g a standardized description o f injuries by following I C D - 9 external cause and nature o f diagnosis codes as was done in this investigation should mitigate a large part o f comparability problems. The sawmill industry contributes significantly to the economy o f the province o f British Columbia. Globally, sawmills are somewhat similar in the work processes, use o f tools and equipment, and handling o f materials; so, findings for this sector in British Columbia should be applicable to other jurisdictions with limited awareness o f the most frequent causes and nature o f sawmill injuries. Information on the types o f injuries and job categories at higher risk can be used to inform the design o f targeted and essential workplace safety interventions in sawmills i n British Columbia and around the world. Work-related injures requiring hospitalization have very high potential o f resulting i n both short-and long-term disability. A s there are likely more work-related injuries reaching hospitals than the compensation agency reports [Shannon and Lowe, 2002; Alamgir et al., 2006], and  hospital  records  are  collected  independently,  this  investigation  provided  a  more  comprehensive description o f serious work-related injuries among the working population in a vital industrial sector. Depending on the coding reliability and validity o f this database, hospital data represents an alternative source o f information for compensation-related  statistics for  144  serious  work-related  injuries.  However,  validity  and  reliability  of  administrative  and  electronically collected databases have been established in some previous studies [Vestberg et al., 1997; Rawson and M a l c o l m , 1995; Kashner, 1998; Beghi et al., 2001]. The findings o f this study should be interpreted carefully due to the following limitations. It did not capture injuries that did not arrive at the hospitals; for example, there might be events, which were treated at the worksite and perhaps were less serious. Secondly, the findings depended solely on the reliability and validity o f the coders in the hospitals. Another important limitation was this study captured only 173 cases - resulting i n small numbers in some injury categories. Future studies should describe injuries among a working population by nature, cause, and body parts involved, and follow a standardized reporting and coding approach.  Consistency i n  injury coding w i l l help to improve generalizability and comparability o f the published studies and reports. The hospital discharge records i n Canada now follow the ICD-10 diagnosis-coding schedule which also has place o f occurrence indicators [ICD-10]. Studies should also collect information on the work history o f the workers including the tasks they perform, age at hire, and experience at different jobs. W o r k characteristics should be investigated in relation to injury characteristics to help better assess the safety hazards. K n o w i n g the causes, nature and body parts involved and standardized description o f injuries w i l l be helpful to employers, compensation officials, and other stakeholders in countries, where sawmills are abundant. For example, the injury information could be used to identify vulnerable worker groups, and subsequently target preventive measures within an industry. Detailed describing o f work-related injuries could also be used to guide regulatory processes and prevention strategies. If injuries among employed persons are not described well, policy and  145  prevention decisions may not be based on accurate or complete evidence and employees may not receive needed safety measures.  146  T A B L E 7.1: NATURE OF INJURY AND CAUSES FOR 173 WORK RELATED HOSPITALIZATIONS  Fracture of skull, intracranium, spine & trunk Fracture-upper limb Fracture-femur, lower limb Dislocation, sprains, strains Open wounds, injuries to blood vessels Superficial injury, crushing, foreign body Burns Other nature of Injuries**  Total  Falls  Fire, Flame, natural, Environme ntal  Struck by falling object  Struck against  Caugh t in or betwe en  Machinery related  Cutting & piercing  Overexertion  Other causes*  Total  3  0  4  7  1  6  1  0  1  23  8  0  2  5  3  7  1  0  1  27  8  0  5  3  2  5  0  0  0  23  9  0  1  3  0  2  0  16  4  35  1  0  0  4  3  17  7  0  3  35  1  0  1  0  0  g  0  0  1  12  0 0  6 1  0 0  0 2  0 0  0 3  0 0  0 0  3 3  9 9  30  7  13  24  9  49  9  16  16  173  * Other cause of injury includes transportation, drowning, suffocation, foreign body; explosion, firearms, hot substances, electricity; other and unspecified ** Other nature of injury includes Internal injury-chest, abdomen, pelvis, injuries to nerves & spinal cord; traumatic complications, non-medicinal substances, unspecified, others  147  T A B L E 7.2: NATURE OF INJURY AND BODY PARTS FOR 173 WORK RELATED HOSPITALIZATIONS  Fracture of skull, intracranium, spine & trunk Fracture-upper limb Fracture-femur, lower limb Dislocation, sprains, strains Open wounds, injuries to blood vessels Superficial injury, crushing, foreign body Burns Other Injuries* Total  Hand & Finger 0  Head, Face & Neck 15  Leg, Knee & Ankle  Shoulder & Arm  Trunk, Back & Groin  Other body parts  Total  0  0  8  0  23  25 8  0 0  0 5  2 2  0 5  0  27  3  23  9  0  1  0  2  3  35  1  0  0  3  17  4  35  1  0  1  0  9  0  12  0 0  6 0  0 0  0 0  0  0 8  9  1  30  7  13  9  49  24  173  9  * Other nature of injury includes Internal injury-chest, abdomen, pelvis, injuries to nerves & spinal cord; traumatic complications, non-medicinal substances, unspecified, others  148  T A B L E 7.3: W O R K - R E L A T E D HOSPITALIZATIONS A M O N G SAWMILL WORKERS BY NATURE, CAUSE AND BODY PARTS INVOLVED  Injury Category  Work-related hospitalization frequency (%)  Work-related Hospitalization Rate per 1000 person-years  Cause of Injury Machinery  related  30(17)  Falls Struck  against  Overexertion Struck by falling  49 (28)  24 (14) 16(9)  object  13(8)  Cutting & piercing  9(5)  Caught in or between  9(5)  Fire, Flame, Natural & Environmental  7(4)  Other Causes  16(10)  1.54 0.94 0.75 0.50 0.41 0.28 0.28 0.22 0.50  Body parts Involved Hand & Finger  57 (33)  Leg, Knee & Ankle  44 (25)  Head, Face & Neck  27(16)  Trunk, Back & Groin  24 (14)  Shoulder & Arm  7(4)  Others  14(8)  Open wounds  35 (20)  1.79 1.38 0.85 0.75 0.22 0.44  Nature of Injury Dislocation,  sprains & strains  1.09  35 (20)  1.09  27 (16)  0.85  23(13)  0.72  23(13)  0.72  injury & crushing,  12(7)  0.38  Burns  9(5)  0.28  Traumatic complications/ non-medicinal substances/ unspecified/others  5(3)  Internal injury-chest, abdomen & pelvis  4(2)  0.13  Total  173 (100)  5.43  Fracture-upper Fracture  of Head and Trunk  Fracture-lower Superficial  limb  limb  0.16  149  T A B L E 7.4: W O R K - R E L A T E D HOSPITALIZATIONS BY JOB CATEGORIES AMONG SAWMILL WORKERS  ^ob^a^e^ory~~  Work-related injury Number (%) _____  Hospitalization Rate per 1000 person-years  Machine operators/attendants/clearers/sorters  51 (29.48)  5.96  Skilled trades (use tools)  48 (27.75)  6.91  Material handling/unskilled  43 (24.86)  5.52  Inspector, grader, other skilled worker (non tool user)  14 (8.09)  4.84  M o b i l e equipment operator  7 (4.04)  2.34  6 (3.47) 3.61  Foreman/Supervisor Non-wood industry & non-production  4(2.31)  3.97  150  T A B L E 7.5: DISTRIBUTION OF WORK-RELATED HOSPITALIZATIONS BY JOB CATEGORIES AMONG SAWMILL WORKERS Material handling/ unskilled  Machine operators/ attendants/ clearers/ sorters  3  13  16  3  Mobile Foreman/ Skilled trades equipment operator Supervisor (Use tools)  Inspector, grader, Non-wood industry & other skilled nonworker (non tool production user)  Total  Cause of Injury Machinery related  1  13  0  49  Falls  2  7  1  8  8  3  1  30  Struck against  0  11  0  7  3  1  2  24  Overexertion  0  6  0  3  5  1  1  16  Struck by falling object  0  2  0  3  8  0  0  13  Caught in or between  0  2  0  3  4  0  0  9  4  0  0  9  0  4  0  7  0  16  Cutting & piercing Fire, Flame, natural, Environmental  0  4  0  1  2  1  0  0  1  2  3  5  3  2  6  48  7  43  51  14  4  173  Hand & Finger  2  17  2  14  17  5  0  57  Leg, Knee & Ankle  2  10  0  14  13  3  2  44  Head, Face & Neck  1  8  2  7  7  1  1  27  Trunk, Back & Groin  0  8  0  5  8  2  1  24  Others  1  2  2  2  4  3  0  14  Shoulder  0  3  1  1  2  0  0  7  Total  6  48  7  43  51  14  4  173  Nature of Injury Dislocation, sprains, strains Open wounds, injuries to blood vessels  2  11  0  9  9  1  3  35  1  9  1  9  11  4  0  35  Fracture-upper limb  0  7  1  7  10  2  0  27  0  6  0  8  8  0  1  23  1  4  0  7  9  2  0  23  Other causes Total Body parts  Fracture of skull, intracranium, spine & trunk Fracture-femur, lower limb Superficial injury, crushing, foreign body  0  5  3  2  2  0  0  12  Burns Traumatic complications, nonmedicinal subs, unspecified, others Internal injury-chest, abdomen, pelvis, nerves & spinal cord  2  3  0  1  0  3  0  9  0  1  2  0  1  1  0  5  0  2  0  0  1  1  0  4  Total  6  48  7  43  51  14  4  173  151  FIGURE 7.1: DISTRIBUTION OF WORK-RELATED INJURY REQUIRING HOSPITALIZATION BY A G E AMONG SAWMILL WORKERS  152  7.5 R E F E R E N C E S  Alamgir H , Koehoorn M , Ostry A , Tompa E , Demers P A . 2006-A. 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Injury rate i n sawmills, p 23-34  157  CHAPTER 8 DISCUSSIONS AND CONCLUSIONS  8.1 K E Y FINDINGS AND POLICY IMPLICATIONS The results o f this study provided significant insights into surveillance, epidemiology, costs, and compensation o f work-related sawmill injuries. The programs o f research o f this dissertation were centred on the use o f hospital discharge records to examine its use as a workrelated injury surveillance tool, estimating the costs and compensation associated with such injuries, and investigate the epidemiology o f these injuries in a study population o f sawmill workers i n the Canadian Province o f British Columbia. There were different but related objectives in the six papers o f the thesis: 1) the first paper examined the validity o f hospital discharge records as a tool for work-related injury surveillance, 2) the second paper tested the capturing patterns o f such injuries by workers' compensation agency compared to hospital discharge records, 3) the third paper assessed the accuracy o f injury diagnosis coding o f workers' compensation records compared to hospital discharge records, 4) the fourth part analyzed costs and compensation patterns o f the injuries, 5) the fifth paper estimated hospitalization costs and compensation patterns o f the injuries, and 6) the last paper conducted an epidemiological investigation o f these injuries. This chapter recaptures and summarizes the key findings and conclusions, describes how these add up to the current state o f knowledge, and addresses some other issues that influence the results and interpretation o f this study, summarizes the strengths and limitations o f the study, and provide some guidelines on future research i n these areas.  158  8.1.1 WORK-RELATED INJURY SURVEILLANCE: HOSPIITAL DISCHARGE DATA AND WORKERS' COMPENSATION DATA Two indicators-ICD-9 external cause o f injury codes and payment codes were available in hospital records to effectively identify serious work-related injuries requiring hospital admissions. The agreement between them i n identifying such injuries was good (Kappa= 0.77). However, it was found that the pattern o f capturing work-related injuries using these two indicators varied by cause o f injury. Together, these two indicators were quite exhaustive in capturing work-related hospitalized injuries as the capture-recapture method results suggested that very few events (about 1%) requiring hospital admissions remained unascertained by these two surveillance indicators. According to the findings on the concordance between workers' compensation claims database and hospital discharge records, the provincial compensation agency in the Canadian province o f British Columbia was found to under-report even the more serious and acute workrelated injuries reaching hospitals by about 10% i n a population actively working i n a large unionized industry. This study also documented several vulnerable groups o f workers, like, older and non-white people, and specific injury categories, like, overexertion  and falls,  that were  related with greater under-reporting. Hospital discharge datasets have comprehensive information on the type and severity o f injuries and depending on coding reliability and validity, they can work as an available and efficient alternative to the provincial compensation agency reports for examining serious injury trends and have the potential to be integrated with the compensation dataset to work as a comprehensive work-related injury surveillance system i n British Columbia. A s work-related injuries are not always reported for compensation and compensation agencies do not compensate  159  all claims filed to them, learning about the causes and nature o f injuries from a different and independent source is useful to regulators and policy makers to identify vulnerable groups o f workers and work-processes and devise preventive measures within an industry. This study also suggests that the W C B data collection systems should be upgraded with detailed information on all types o f injuries irrespective o f their severity (e.g., it could collect injury information on health care only claims representing less serious injuries). To improve the compensation patterns, education and training o f the susceptible group o f workers and their supervisors on the compensation system and claim filing method at workplaces, and precautionary measures taken by the compensation claims handlers to deal with the claims from the vulnerable workers and for the commonly under-compensated injury types might be useful. Surveillance data are essential both to establish the need for public health action and to assess the effectiveness o f interventions. The injury surveillance programs should seek to reduce serious injuries by monitoring the incidence, trends, risk factors and circumstances o f these injuries and disseminating this information to injury prevention advocates. These data should be useful to inform and influence decision-making regarding the development and evaluation o f injury prevention initiatives and policies. A s described i n the beginning o f the thesis and i n Figure 1.2, there were work-related injuries that were beyond the scope o f this investigation. A n injury coded as occurred in a workplace might not always be work-related. To differentiate a work-related case from a non-work related case in the workplace was not possible by the tools the current study helped to develop and proposed to use. There were other work-related injuries that did not reach hospitals or were not filed for claims, and there were some other cases that were not work-related but were claimed for compensation. The compensation system has claim adjudication process where their  160  experts decide about the acceptance and amount o f compensation for each claim. There is also an appeal process where workers can challenge a decision. But, surely some claims remain unaccepted or under-compensated. The workers' compensation system's data on rejected claims w i l l help the researchers to dig into more which injuries have higher likelihood o f being rejected. Unless these records are made available, workers o f particular types and injuries o f particular nature might continue to be uncompensated. A l s o , inaccuracy i n the hospital records, like, coding error and missing data might result in overestimation o f some injuries as work-related. A m i d widespread argument and counter argument o f under-compensation and defrauding with the workers' compensation system, independent investigation as done by this thesis would provide immensely helpful information in the occupational health and safety arena. In addition, there w i l l be some injury cases where establishing work-relatedness w i l l be inherently difficult because o f the unusual circumstances. These important issues were not within the scope o f the current thesis. Further research is required on under-compensation, rejection o f a genuine claim, shortcomings o f adjudication and appeal processes, claims for non work-related injuries, and filing for fraudulent claims. The study findings suggest that a comprehensive work-related injury surveillance system should be developed independent from the compensation system. The compensation system can be used i n combination with the hospital discharge records as suggested by these study findings to be more comprehensive to include more cases, but, since the hospital records only captures serious injuries, the potential for underreporting w i l l exist. A more direct injury data collection system should be developed that can report all incidence to an independent data collection and research agency. Irrespective o f claim approval status, this agency might work as data store house for all work-place injury and perform necessary analysis to produce policy related  161  documents and reports from all these injuries. Standard reporting forms can be developed to use in workplaces where employees and supervisors can independently fill relevant portions. This standard form should also collect information about the hazards present and describe the corrective actions taken by the employer to eliminate or reduce the hazards. It might also collect information on near misses so that organizations can be pro-active in preventing injuries. This injury surveillance system should also gather information on nature and cause o f an injury and also identify the body parts involved. From prevention aspect, the cause o f injury is more useful, but for diagnostic and clinical outcome and costs estimation, nature o f injury is more meaningful. The body parts involved in an injury w i l l also help develop means for safeguarding. Workers' compensation datasets are widely used by researchers and policy makers as a tool for injury surveillance; therefore, investigating the accuracy o f their injury codes was imperative. Our study also examined the accuracy o f the injury related diagnosis codes o f the compensation system holding hospital discharge dataset as the comparative standard. V e r y few published studies provided insight into the level o f error to be expected for the injury codes in the compensation systems. Overall, despite the limitations o f our methodology, this study found good agreement on injury codes between the two data sources (Kappa was 0.63 for nature o f injury, and 0.71 for body parts) which strengthened the support for using compensation datasets for occupational epidemiology investigations and research in British Columbia. However, the findings suggested that the accuracy o f injury codes was stronger for sharp and acute type injuries (burns and fracture of lower limbs) and weaker for superficial injuries. Training o f the coders o f both hospitals and compensation agency on data extraction, injury coding and I C D systems, and frequent reliability and validity testing on the important  162  variables w i l l provide greater confidence on using these datasets. It w i l l be helpful i f the coders understand the various uses o f the codes beyond administrative or financial tasks - importance o f codes from other perspectives as well. Cooperation and collaboration o f records keeping and data coding between the hospital staff and compensation agency staff should be encouraged to create more comparability for these data sources. The study findings also suggested that claims datasets follow a more standardized approach o f injury coding as recommended by the I C D systems (nature and cause codes), so that their data can be effectively used and compared across other sources and studies.  8.1.2 E P I D E M I O L O G Y O F W O R K - R E L A T E D S A W M I L L I N J U R Y The epidemiological investigation using the hospital discharge records found the overall injury rate for work-related hospitalization to be 5.4 per 1,000 person years during the ten-year follow-up period. During the study period, the most frequent causes o f injury were machinery related, falls and being struck against, and in terms o f body parts, the hand & finger were associated with a third o f all injuries followed by the leg, knee & ankle, which made up one fourth. The job groups that were at high risk o f sustaining serious injuries were skilled trades followed by machine unskilled  operators,  attendants, clearers  & sorters  and material  handling  &  workers.  A s sawmills worldwide are to some extent comparable i n the work processes, use o f tools and equipment, and handling o f materials; epidemiological findings like these in British Columbia should be relevant to other jurisdictions. Information on the types o f injuries and job categories at higher risk can be used to inform designing o f targeted and essential workplace safety interventions i n sawmills in British Columbia and around the world.  163  Studies like this focusing on the descriptive epidemiology o f injury update on the proximal etiology o f injuries. Though, new advances in the prevention o f such injuries w i l l necessitate a more systematic approach to understanding the complex array o f factors that influence the incidence and outcomes o f injury. Simultaneously, it is important for investigators to conduct rigorous evaluations o f new interventions to better inform the establishment o f programs and policies.  8.1.3 ECONOMIC CONSEQUENCES OF WORK-RELATED INJURY Thus study reported that the median costs for non-health care services (in 1995 Canadian Dollars) were $16,559 per injury and for healthcare were $4,377 per injury during the study period (1989-1998). Our study identified the injury categories that had a high probability o f resulting in long-term disability (for example, caught in or between, and fire, flame, natural & environmental).  B y median costs, fire, flame, natural & environmental  was identified as the  most costly causes o f injury. It also suggested that a substantial amount o f the costs o f work-related serious injuries remained un-captured or uncompensated. About 10% o f the serious and acute work-related injuries were not matched to a workers' compensation claim. The injuries without a workers' compensation claim were associated with 9% o f the total costs o f $12.14 million. These costs were eventually transferred to other parts o f the social safety net including the public health care system. This study also investigated hospital costs separately as incurred following an injury as it makes up a large component o f the total healthcare costs. Costs were estimated from the health care system's perspective. Fire, flame, natural & environmental had the longest median stay (18  164  days) i n hospitals and the highest median cost ($10,575). These findings highlight the high expenses associated with the treatment o f acute work-related injuries, much o f which results from the length o f hospital stay. The provincial compensation agency apparently did not compensate 12% o f the total hospital costs ($434,990). Findings on the cost o f workplace injury play an important role in occupational safety initiatives. K n o w i n g the associated costs and the category o f costly injuries are helpful to the employers, compensation officials, and other stakeholders to identify vulnerable job groups and work processes. Findings on costs highlight that avoiding one injury event can save significant amount o f resources and also help to estimate how cost-effective an intervention is. This information can then be used to design and implement targeted preventive measures within an industry. Injuries among employed persons are to be appropriately compensated so that policy and prevention decisions are based on accurate and complete burden; otherwise, the costs o f some work-related injuries w i l l continue to be paid by other social safety mechanisms. The hospitals and compensation agencies should work together to resolve some o f these issues regarding identifying and billing all eligible injuries. This study also highlighted that it is not mandatory for the traditional compensation system to compensate many o f the costs associated with a work-related injury. The burden on the society for a long-term disability case is massive. The spouse and family members o f an injured worker also suffer when the earning member's work life is drastically shortened because o f an injury. Quality o f life and other methodological research is ongoing to study the costs o f pain, suffering and other emotional consequences. From the employer's side, costs associated with loss o f productivity, hiring and retraining, loss o f employee morale are huge but so far remain unstudied. Methods to estimate most o f these costs associated an injury are yet to be developed.  165  The implications o f the study findings w i l l be different for the employers, employees, workers' compensation system and the public health care system. For example, i f more injuries can be identified as work-related than compensated, to reimburse for those cases workers' compensation system might try to charge higher premiums from the employers; employers might try further to implement better safety environment to avoid a raise i n the premiums and improve employee morale and productivity; employees, through unions, might try to push for proper compensation from the compensation system and might suggest the employers to provide safer workplaces; the public healthcare system might try to recover some o f the healthcare costs from the compensation system.  8.2 S T U D Y S T R E N G T H S A N D L I M I T A T I O N S  8.2.1 S T R E N G T H S This study has a number o f specific strengths that enhance the credibility o f the results. First o f all, it used two administrative data sources. These data are collected for administrative reasons, and are readily available, easy to access, and inexpensive. These are especially suitable for retrospective studies covering longer periods o f observation. Hospital discharge records have detailed information on the injuries and the records are collected objectively. Workers' compensation claims data represents an important source o f information on work-related injuries. These are compiled using officially reported and accepted claims, and provide detailed information on the causes and costs o f injury.  166  Secondly, it used a large study population from large, unionized sawmills. The population was employed in an important and high risk workplace setting to investigate the work-related injury surveillance. Their detailed demographic and work-history information was collected as part o f previous studies. The job history had information on each job they held during their work life i n sawmills and the exact start and end dates. Thirdly, to link and match the claims records with the hospitalization records, this study did not use any complicated formula; it relied simply on injury diagnosis and date information. This should make it easy to replicate such linking in other jurisdictions for such data sources. For economic analyses, the actual compensated costs for each claim were captured rather than estimating these from secondary sources or using average claim costs. The dollar values were expressed in constant Canadian dollars by using consumer price index and discount rates. For estimating hospital costs this study used a detailed and accurate collation o f billing charts from which costs were derived- the billing rate was year and hospital specific. Each patient-day was accounted for. Use o f the cost per weighted case or Cost per Resource Intensity Weight (RIW) methodology was avoided as it is fairly complicated, not fully developed or verified. This is not also how the hospitals currently b i l l the compensation agency for workrelated hospitalizations. Finally, this study's use o f hospital discharge records is itself a strength. Because o f the public health care system i n Canada which provides comprehensive coverage o f hospitalizations at the population level, hospital data has potential to capture serious injuries. Almost all eligible residents o f B C are enrolled with the provincial Medical Services Plan and the plan captures all  167  medical services records o f physicians, specialists, other health care practitioners, laboratory services, and diagnostics services and hospitalizations.  8.2.2 L I M I T A T I O N S A s with any study, this one is not without limitations, but none o f this significantly affected the findings. Use o f hospital discharge records precludes any injury that does not reach hospitals. Thus, this study captured and focused only on serious injury. Hospital discharge records w i l l never be an independent tool i n the strict sense. But it was assumed that serious enough injuries require more attention as they result i n more misery and suffering for workers and consume more resources o f the society. Moreover, it is expected that most o f these significant cases be compensated and should have matching claims i n the workers' compensation datasets. This study depended heavily on the accuracy o f the codes available in hospital data. However, numerous studies outside Canada and inside Canada have used hospital discharge datasets and other administrative datasets. The reliability and validity o f hospital records were favorably examined by some studies. Use o f electronically available administrative data is increasingly becoming common in research studies. There is no gold standard for work related injury surveillance tools. The workers' compensation agency does not capture, accept, or report on all injuries. While there are complaints o f underreporting to the workers' compensation authority, it should be sensitive enough to capture information on injuries severe enough to reach a hospital. Matching o f a work related hospital record with actual claim can help validate compensation records as a potential surveillance tool.  168  Another limitation o f the study was unavailability o f data on rejected claims i n the workers' compensation dataset. I f this data were available, is would have been possible to differentiate between injuries identified i n the hospital discharge dataset that were never recognized by the compensation system versus those that were submitted and subsequently rejected.  This information w i l l add value to such study by investigating the agreement o f  rejected claims with the responsibility o f payment and place o f occurrence fields. However, even with rejected claims data it would not be possible to differentiate between claims that were appropriately versus inappropriately rejected.  A n underlying assumption i n this thesis is that  claims identified as potentially work-related were indeed work-related. Despite the favorable comparison between data from the hospitalization database and compensation databases, this study cannot establish the true validity o f clinical data from the compensation databases because the hospitalization database is not a gold standard; but the agreement between these two independent sources o f data lends some credence to the clinical information that can be ascertained from claim records. This study had a number o f limitations in its linking methodology. A 1-month window beyond admission and separation dates was used for the initial linkage strategy. This captured primarily acute work events needing immediate health care attention; injuries that were admitted to hospital after a long latent period were excluded from our linking strategy. A broad injury category rather than exact I C D - 9 code was used to match the linked cases that occurred during the 1 -month window between the two data files. This was allowed because the injuries were coded by two different organizations, which should be able to match on broad injury categories but not necessarily on the specifics o f the injury. However, an individual might  169  sustain two injuries within the time window, which were o f same broad category injury, but were indeed different events. A matching criterion o f even 1 day could also link two disparate events. The W C B file does not have detailed information on injuries for health care-only claimswhich limits its use as a comprehensive data source for all claimed injuries. But this study looked at serious injures requiring hospitalization, which were unlikely to be health care only claims. The costs estimated were not comprehensive for all injuries i n this sector. Cost information was available up to 2005, which provided 7 years to develop costs for all the injury events studied, as the last injury captured i n our study occurred i n 1998. However, it is likely that major costs were developed within the first 7 years after an injury event. The method o f using daily charge for hospital stays has limitations. For example, it considered all injuries consumed similar amount o f resources per day. However, when exploring the billing relationship between the hospitals and the compensation agency, it is appropriate to use this rate. This study argues that when Ministry sets the daily rates, it should incorporate overhead and administrative costs o f the hospitals into it. The cost estimates were likely to be underestimates  o f societal costs because the  perspective o f the workers' compensation agency was taken. This perspective ignores costs such as those associated with pain and suffering as well as those related to home care, lost leisure time, out o f pocket expenses for the worker or spouse/family members, ambulance fees, retraining, recruiting, and overtime costs for the employers. There was insufficient information available to include all these costs. However, as the compensation agency covers some important cost components associated with an injury, the costs captured in this study should have included most o f these significant costs.  170  8 . 3 FUTURE RESEARCH This thesis highlights the needs o f and helps to guide future research studies to enrich the understanding o f surveillance o f occupational injury and the associated economic consequences. Foremost, it suggests and recommends the use o f hospital discharge records as a potential source of information on serious work-related injuries. Occupational health researchers can use this rich data source to study acute and serious injuries across different regions, industries, occupational groups and study populations. It suggests that future studies should describe injuries among a working population by nature, cause and body parts involved, and follow a more standardized approach i n reporting them so that study findings can be compared and generalized with greater ease. It also establishes the validity o f workers' compensation data sources so that injury researchers and policy makers can use this information with greater confidence. Further research is warranted to enhance validity o f and comparability between the hospital records and claims records. Future research should also target to establish validity and reliability o f other commonly used administrative data sources in occupational safety. Studies with larger working population from a m i x o f different industrials sectors w i l l help better determine the accuracy o f injury coding in such data sources. They might also suggest better ways o f linking and matching different data sources. The workers' compensation agencies should solicit and undertake investigations why some segments o f the working population are not reporting or getting compensation for workrelated incidents. The barriers that prevent them from claiming (for example, language and unfamiliarity with the system) need to be identified in today's workplace, which is more  1 7 1  multicultural and multiethnic than ever before. More studies should look into other likely barriers- discouraging supervisors and colleagues, age and experience o f workers, sex, physician participation, delay in compensation, etc.  Future cost studies might incorporate costs such as those associated with pain and suffering as well as those related to home care, lost leisure time, out o f pocket expenses for the worker or spouse/family members, ambulance fees, retraining, recruiting, and overtime costs for the employers. A s it is recommended to calculate costs o f an illness or injury from the societal perspective so that all costs are included irrespective o f where the burden falls, future studies should look into it, and estimate how much o f the total costs the provincial compensation bodies are covering, and what other cost categories should be covered by them instead o f shifting the burdens to the employees, employers, or other social safety nets. Additional studies can explore how much is the retraining, hiring, and training cost to the employers to replace an injured worker. Such findings w i l l encourage employers to instate interventions to save their own resources. The short-term and long-term disability costs the compensation systems are paying should be investigated to see how much the injured workers are actually getting compared with the earning trajectory o f non-injured workers with similar education and experience. Future hospital cost studies could improve upon this study by incorporating differential resource consumption patterns by injury cases within each hospital. Further research is also necessary to identify the circumstances surrounding the diversion o f these costs from the workers' compensation system to the public health care sector. Future epidemiological investigations can compare and contrast risk factors o f all workrelated injury and hospitalized work-related injury. Extracting detailed information on the work  172  history o f the workers including the tasks they perform i n a job, the work processes, the physical hazards, age at hire, and experience at different jobs w i l l help elaborately and credibly assess the safety hazards i n an industrial sector.  173  

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