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Time on wait lists for coronary bypass surgery in British Columbia, Canada, 1991 - 2000 Levy, Adrian R; Sobolev, Boris G; Hayden, Robert; Kiely, Michael; Mark FitzGerald, J; Schechter, Martin T Mar 14, 2005

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ralssBioMed CentBMC Health Services ResearchOpen AcceResearch articleTime on wait lists for coronary bypass surgery in British Columbia, Canada, 1991 – 2000Adrian R Levy*†1,2, Boris G Sobolev†1,3, Robert Hayden4,5, Michael Kiely5, J Mark FitzGerald1,3 and Martin T Schechter1,2Address: 1Department of Health Care and Epidemiology, University of British Columbia, Vancouver, Canada, 2Centre for Health Evaluation & Outcome Sciences, St. Paul's Hospital, Vancouver, Canada, 3Centre for Clinical Epidemiology and Evaluation, Vancouver General Hospital, Vancouver, Canada, 4Department of Surgery, Royal Columbian Hospital, Vancouver, Canada and 5British Columbia Cardiac Registries, St. Paul's Hospital, Vancouver, CanadaEmail: Adrian R Levy* - alevy@cheos.ubc.ca; Boris G Sobolev - sobolev@interchange.ubc.ca; Robert Hayden - erh@telus.net; Michael Kiely - mkiely@telus.net; J Mark FitzGerald - markf@interchange.ubc.ca; Martin T Schechter - martin.schechter@ubc.ca* Corresponding author    †Equal contributorsAbstractBackground: In British Columbia, Canada, all necessary medical services are funded publicly.Concerned with growing wait lists in the mid-1990s, the provincial government started providingextra funding for coronary artery bypass grafting (CABG) operations annually. Although aimed atimproving access, it is not known whether supplementary funding changed the time that patientsspent on wait lists for CABG. We sought to determine whether the period of registration on waitlists had an effect on time to isolated CABG and whether the period effect was similar acrosspriority groups.Methods: Using records from a population-based registry, we studied the wait-list time before andafter supplementary funding became available. We compared the number of weeks fromregistration to surgery for equal proportions of patients in synthetic cohorts defined by fiveregistration periods in the 1990s.Results: Overall, 9,231 patients spent a total of 137,126 person-weeks on the wait lists. The timeto surgery increased by the middle of the decade, and decreased toward the end of the decade.Relative to the 1991–92 registration period, the conditional weekly probabilities of undergoingsurgery were 30% lower among patients registered on the wait lists in 1995–96, hazard ratio (HR)= 0.70 (0.65–0.76), and 23% lower in 1997–98 patients, HR = 0.77 (0.71–0.83), while there wereno differences with 1999–2000 patients, HR = 0.94 (0.88–1.02), after adjusting for priority groupat registration, comorbidity, age and sex. We found that the effect of registration period wasdifferent across priority groups.Conclusion: Our results provide evidence that time to CABG shortened after supplementaryfunding was provided on an annual basis to tertiary care hospitals within a single publicly fundedhealth system. One plausible explanation is that these hospitals had capacity to increase the numberof operations. At the same time, the effect was not uniform across priority groups indicating thatchanges in clinical practice should be considered when adding extra funding to reduce wait lists.Published: 14 March 2005BMC Health Services Research 2005, 5:22 doi:10.1186/1472-6963-5-22Received: 24 September 2004Accepted: 14 March 2005This article is available from: http://www.biomedcentral.com/1472-6963/5/22© 2005 Levy et al; licensee BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.Page 1 of 10(page number not for citation purposes)BMC Health Services Research 2005, 5:22 http://www.biomedcentral.com/1472-6963/5/22BackgroundPatient access to care within a certain time is an importantperformance indicator of health systems[1,2]. In publiclyfunded health care, wait lists are commonly used to man-age access to elective procedures raising concerns aboutdelaying necessary treatment[3,4]. In patients with coro-nary artery disease (CAD) requiring coronary arterybypass graft (CABG) surgery, delaying the operation maylead to deterioration in the patient's condition, worseningof clinical outcomes and increased risk of death[5,6].Queuing CAD patients according to urgency of treatmentis generally perceived as a method of facilitating access tocare within clinically appropriate time[6].In the Canadian province of British Columbia (BC), allmedically necessary services are publicly funded[7]. Con-cerned with growing wait lists for cardiac surgery in themid-1990s the provincial government started providingsupplementary funding to increase the number of CABGoperations by 15% annually starting in 1998[8]. Althoughaimed at improving access, it is not known whether thesemeasures changed the time patients spent on CABG waitlists.Previous studies showed inconsistent results regarding theimpact of supplementary funding on time to surgery inexisting hospitals in publicly funded health systems[9]. Ithas been suggested that the effect may vary according tothe scope and the term of funding commitment, such assingle hospital versus all the hospitals in a region, and onetime versus on-going increases[10]. Although access tosurgery from wait lists depends on the assigned priority,there is little information on the impact of supplementaryfunding across different priority groups.In this paper we compare the number of weeks betweenbeing registered for CABG and undergoing the operationfor equal proportions of patients registered in differentyears before and after the provincial government startedproviding supplementary funding. In the study period,patients were prioritized according to the establishedguidelines to expedite access to surgery if they were con-sidered at greater risk of deterioration or death. The spe-cific research questions were: 1) did the period ofregistration have an effect on the time patients spent onwait lists for CABG? 2) was the period effect similar acrosspriority groups?We use all relevant records from the provincial popula-tion-based registry of CAD patients identified as needingbypass surgery. Primary comparisons are done across syn-thetic cohorts of patients defined by two-year periods ofregistration on the wait lists: 1991–92, 1993–94, 1995–MethodsData sourcesThe provincial Cardiac Surgery Registry, a part of BC Car-diac Registries, was created in 1990 to collect data forreporting, planning and research purposes of participat-ing surgeons and hospitals, and the provincial Ministry ofHealth[11]. The Registry prospectively captures the occur-rence and timing of registration, surgery, or removal fromthe wait lists without surgery, for all patients accepted forcardiac surgery procedures in the four hospitals deliveringall adult open-heart surgery services to four million resi-dents of BC.Between 1991 and 2000, from 15 to 20 cardiac surgeonswere performing bypass surgery in BC, with less than 30%turnover. Although cardiac surgeons manage their waitlists independently, they all routinely provide informa-tion to the Registry entry modules: surgery registration,operative report, wait-list reconciliation, and dischargesummary. When accepting patients on their wait lists, thesurgeons document the indication for the procedure aswell as the priority for treatment using common criteria(see below).Once the operation is completed, the operative reportcontaining the procedure and clinical data is entered inthe Registry. Patients are removed from the wait lists afterundergoing the operation or for other reasons: if theydied, declined the operation, accepted surgery fromanother surgeon, moved away, or switched to medicalmanagement. The crude agreement between the Registryand hospital charts for ten demographic and clinical dataelements has been estimated at 86%[11].We deterministically linked the Registry records to admin-istrative databases storing records of all hospital episodesin BC[12]. These records include the dates of admission,procedure and discharge, as well as diagnoses at dis-charge[13]. These data were used to corroborate the serv-ice dates and to identify coexisting medicalconditions[14].PatientsIf angioplasty is not indicated when the cardiologist eval-uates the arterial lesions on the coronary angiogram, thena cardiac surgeon is consulted to assess the patients' suita-bility for CABG. Patients are transferred to an in-patientward directly from the catheterization laboratory if expe-dited assessment is necessary. If deemed suitable, thesepatients wait for CABG in hospital without registration ona wait list. Alternatively, a consultation with the surgeoncan be scheduled at a later date. Surgeons register on theirwait lists patients who need CABG and for whom thePage 2 of 10(page number not for citation purposes)96, 1997–98, or 1999–2000. operation can be safely delayed. As in-patients were notBMC Health Services Research 2005, 5:22 http://www.biomedcentral.com/1472-6963/5/22added to wait lists, they were not included in analyses ofwait-list times.There were 9,366 records of registration for isolated CABGadded to the Registry between January 1991 and Decem-ber 2000. We excluded 135 records of patients who were:emergency cases (30), removed on the registration date(101), and had missing operating room reports (4). Allremaining 9,231 records had either the surgery date or thedate and reason of removal from the list without surgery.We restricted the analyses to the first 52 weeks after regis-tration so that 475 (5%) patients remaining on the lists at12 months were censored. Of those, 167 eventuallyunderwent surgery; seven died; 78 received medical treat-ment; 104 declined surgery; 17 were transferred toanother surgeon or hospital; and 102 were removed forother reasons.Priority groupsWhen assigning priority, all cardiac surgeons in BC applycommon guidelines developed in 1990 [see Additionalfile 1]. Using the location and degree of affected coronaryanatomy and symptoms, the guidelines help to: identifypatients for whom CABG can increase survival or improvequality of life[15]; classify patients according to urgencyof treatment; and assign a maximum recommended wait-ing time (MRWT). Patients are assigned priority 1 if theyrequire CABG urgently (eg, left main coronary artery sten-osis greater than 70%, MRWT three days); priority 2 ifthere is moderate urgency (eg persistent unstable angina,MRWT six weeks); or priority 3 if there is less urgency (egintractable chronic angina, MRWT 12 weeks). Theseguidelines did not undergo any major revisions throughthe entire period under study.ComorbidityUsing the administrative data, coexisting medical condi-tions were identified using all primary and secondary dis-charge diagnoses recorded in all hospital dischargeabstracts within one year prior to registration[13]. Thistime frame was chosen in order to capture the presence ofchronic diseases that could have affected the waitingtime[14].For each patient, we identified the presence of major andminor comorbid medical conditions present atregistration.Statistical methodsWaiting times were analyzed as prospective observationsbeginning at the time of registration. Each subject had await-list time calculated in calendar weeks from registra-tion to surgery or removal for other reasons. The cumula-method[16]. Patients removed from the list for reasonsother than surgery were treated as censored observations.Primary comparisons were done across synthetic cohortsof patients defined by two-year periods of registration onthe wait lists. Differences in the distributions of wait-listtimes across cohorts were examined using the log rank-test[17]. The average weekly surgery rate was calculated bydividing the number of operations by the total number ofpatient-weeks on the list. The effect size for each registra-tion period was estimated by hazard ratios for surgeryderived from a Cox proportional hazards model[18]. Haz-ard ratios (HR) associated with registration periods evalu-ated the conditional weekly probability of undergoingCABG relative to the 1991–92 period. The priority groupsand the presence of comorbidity at registration wereincluded as independent variables in the Cox model toestimate adjusted effects. Age and sex were entered intothe regression models as strata variables to avoid the pro-portionality assumption on these factors while using theproportional hazards model.Table 1: Characteristics of 9,231 subjects registered for isolated coronary artery bypass surgery in British Columbia, 1991–2000.Characteristic N (%)Age group (y)<50 732 (7.9)50–59 2005 (21.7)60–69 3530 (38.2)70–79 2770 (30.0)≥ 80 194 (2.1)SexWomen 1634 (17.7)Men 7597 (82.3)Urgency at registrationPriority 1 659 (7.1)Priority 2 6496 (70.4)Priority 3 1963 (21.3)Unknown 113 (1.2)Major comorbidity at registrationNone 4769 (51.7)Minor comorbidity 2450 (26.5)CHF, diabetes, COPD, rheumatoid arthritis, cancer2012 (21.8)Registration period1991–1992 1724 (18.7)1993–1994 1889 (20.5)1995–1996 2010 (21.8)1997–1998 1888 (20.5)1999–2000 1720 (18.6)Abbreviations: CHF – congestive heart failure COPD – chronic obstructive pulmonary diseasePage 3 of 10(page number not for citation purposes)tive probability of undergoing surgery as a function ofwait-list time was estimated using the Kaplan-Meier The Clinical Research Ethics Board of the University ofBritish Columbia approved the study protocol.BMC Health Services Research 2005, 5:22 http://www.biomedcentral.com/1472-6963/5/22ResultsIn BC in the 1990s, 9,231 patients were registered on waitlists for CABG and spent a total of 137,126 person-weekswaiting. Over the same period, 9,433 patients underwentisolated CABG without registration on wait lists. The mostprevalent groups at registration were men (82%), thosewithout major comorbidities (52%), those registered inpriority group 2 (70%), patients aged 60–69 (38%) and70–79 (30%) years, and those registered in 1995–96(22%), Table 1. The proportion of patients registered inpriority group 1 was lowest in 1999–2000 and highest inthe 1995–96 cohort, Table 2. The opposite pattern wasobserved in priority group 3. Of 8,756 patients who leftthe lists within 52 weeks: 7,991 underwent surgery; 90died while waiting; 176 received medical treatments; 188declined surgery; and 311 were removed due to otherreasons.In all registration cohorts combined, the average weeklynumber of operations was 5.8 (95% confidence interval5.7–6.0) per 100 patients listed, the median time on thelist was 11 weeks (25th percentile 5 weeks; 75th percentile22 weeks), and the probability of undergoing surgery after26 weeks on the list, twice the MRWT for priority group 3,was 20%.As expected, there were significant differences among pri-ority groups, with larger proportions undergoing CABG atevery week among more urgent patients (log rank test =1611.9, P < 0.0001). The average weekly number ofoperations per 100 patients on the list differed from 20.6(19.0–22.2) in group 1 to 6.7 (6.5–6.8) in group 2 to 3.3(3.1–3.4) in group 3. However, considerable variation inwait-list times was observed within each priority group.For instance, although half of group 1 underwent surgerywithin two weeks and 90% underwent surgery by 12weeks, the remaining 10% waited another 1 to 32 weeksThis can be seen in Figure 1, which shows access probabil-ities for CABG in each priority group. The abscissa showsthe number of weeks on the waiting list and the ordinateshows the probability of undergoing operation by thatweek. Higher probabilities correspond to shorter wait listtimes. While all patients were removed at 52 weeks, forgraphical simplicity we show the first 36 weeks. Accessprobabilities in priority 3 (blue) were systematically lowerindicating longer wait list times than among priority 2(red line) or priority 1 (green line).Access to surgery by registration periodThe differences in the proportion of patients undergoingCABG were significant across registration periods (logrank test = 97.3, P < 0.0001), with longer wait-list timesfor those registered between 1995 and 1998, Figure 2.Table 3 shows the number of weeks required for a speci-fied proportion of patients to undergo the operationacross registration periods. Wait-list times in 1995–96were such that 10%, 25%, 50%, and 75% patients under-went surgery within 1, 6, 15, and 26 weeks, respectively,whereas half of the 1991–92 cohort underwent surgerywithin 9 weeks, and 75% did so within 19 weeks. Com-paring the 1995–96, 1997–98 and 1999–2000 cohorts weobserved a compression in access to surgery, i.e., reduc-tion in the length of wait-list interval required for a speci-fied proportion to undergo the operation. As measured bythe difference between 90th and 50th percentiles of the waittime distributions, 40% of the 1995–96 cohort under-went surgery within 33 weeks following the median time,while it took 29 weeks for the 1999–2000 cohort.While the median wait-list time was 11 weeks (the MRWTof priority group 3) in all cohorts combined, 15% of the1991–92 and 1993–94 cohorts, 22% of the 1995–96cohort, 19% of the 1997–98 cohort, and 14% of theTable 2: Distribution of subjects registered for isolated coronary artery bypass surgery in British Columbia, 1991–2000, by priority group and registration periodRegistration Priority 1 Priority 2 Priority 3period N (%) N (%) N (%)1991–1992 116 (6.7) 1221 (70.8) 334 (19.4)1993–1994 110 (5.8) 1381 (73.1) 388 (20.5)1995–1996 249 (12.4) 1363 (67.8) 374 (18.6)1997–1998 117 (6.2) 1327 (70.3) 428 (22.7)1999–2000 67 (3.9) 1204 (70.0) 439 (25.5)Note: Excludes 113 subjects with unknown priorityPage 4 of 10(page number not for citation purposes)(total 13 to 44 weeks). 1999–2000 cohort experienced an excessive wait, definedas longer than 26 weeks (data not shown). The averageBMC Health Services Research 2005, 5:22 http://www.biomedcentral.com/1472-6963/5/22weekly number of operations per 100 patients listed var-ied from 6.5 (6.2–6.9) in the 1991–92 cohort to 5.1 (4.8–5.3) in the 1995–96 cohort to 6.2 (5.9–6.6) in the 1999–shown in Table 4, columns 6 and 7. Relative to the 1991–92 cohort, the conditional weekly probabilities of under-going surgery were 30% lower among 1995–96 patients,Estimated probabilities of undergoing isolated CABG within a certain time after registration on wait lists, by priority groupFigure 1Estimated probabilities of undergoing isolated CABG within a certain time after registration on wait lists, by priority group.<1 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 3600. Group:Waiting Time (Weeks)ProbabilityofUndergoingSurgeryPage 5 of 10(page number not for citation purposes)2000 cohort, Table 4 (fourth column). Correspondinghazard ratios and 95% confidence intervals (CI) areHR = 0.70 (0.65–0.76), and 23% lower in 1997–98patients, HR = 0.77 (0.71–0.83), after adjusting for prior-BMC Health Services Research 2005, 5:22 http://www.biomedcentral.com/1472-6963/5/22ity, comorbidity, age and sex. There were no differencesbetween periods 1991–92 and 1999–2000, HR = 0.94(0.88–1.02).Access to surgery by registration period within priority groupsIn each priority group, the proportions of patients under-going CABG at each week on the wait-list was lowerEstimated probabilities of undergoing isolated CABG within a certain time after registration on wait lists, by registration periodFigure 2Estimated probabilities of undergoing isolated CABG within a certain time after registration on wait lists, by registration period.<1 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 3600. Period:Waiting Time (Weeks)ProbabilityofUndergoingSurgeryPage 6 of 10(page number not for citation purposes)among those registered in 1995–96 compared to 1991–92 as measured by log-rank tests (priority 1: chi-square =BMC Health Services Research 2005, 5:22 http://www.biomedcentral.com/1472-6963/5/225.6, P = 0.0183, 1 df; priority 2: chi-square = 58.2, P <0.0001, 1 df; priority 3: chi-square = 20.5, P < 0.0001, 1df). By 1999–2000, the pattern of change was differentbetween priority groups.In priority group 1, the average weekly number of opera-tions per 100 patients listed declined from 42.4 (34.6–50.2) in the 1991–92 cohort to 20.3 (17.7–22.9) in the1995–96 cohort to 12.2 (9.2–15.3) in the 1999–2000cohort (data not shown). Corresponding HRs and 95%CIs are shown in Table 5, columns 2 and 3. The condi-tional weekly probabilities of undergoing surgery were34% lower for the 1995–96 cohort, HR = 0.66 (0.50–0.87), and 53% lower for the 1999–2000 cohort, HR =0.47 (0.33–0.68), relative to 1991–92. There was a differ-ence in the distribution of wait-list times between 1995–96 and 1999–2000 cohorts (chi-square = 9.9, P = 0.0017,1 df).the 1991–92 cohort to 5.3 (5.0–5.6) in the 1995–96cohort to 7.3 (6.9–7.7) in the 1999–2000 cohort. Theadjusted HR in 1999–2000 was 0.99 (0.90–1.08) relativeto 1991–92 (Table 5, columns 4 and 5). There was no dif-ference in the distribution of wait-list times between1991–92 and 1999–2000 cohorts (chi-square = 0.5, P =0.5, 1 df).In priority group 3, the average weekly number of opera-tions per 100 patients listed changed from 3.9 (3.4–4.3)in 1991–92 to 2.8 (2.4–3.1) in 1995–96 to 4.0 (3.6–4.5)in 1999–2000. The adjusted HR associated with the1999–2000 registration period was 1.07 (0.90–1.26) rela-tive to 1991–92 (Table 5, columns 6 and 7). There was nodifference between the between 1991–92 and 1999–2000cohorts (chi-square= 0.6, P = 0.4, 1 df).DiscussionIn this paper we studied the amount of time that patientsTable 3: Percentiles of wait-list time (weeks) for subjects registered for isolated coronary artery bypass surgery in British Columbia 1991–2000 by registration periodRegistration period Percentile10th 25th 50th 75th 90th1991–1992 1 3 9 19 441993–1994 2 4 9 18 451995–1996 1 6 15 26 481997–1998 2 6 14 25 431999–2000 3 6 10 19 39All periods 2 5 11 22 44Note: probability of undergoing outpatient surgery within 26 weeks of registration is 0.804Table 4: Average weekly rate of undergoing the operation from wait list for isolated coronary artery bypass surgery in British Columbia 1991–2000 and adjusted rate ratios by registration periodRegistration periodNumber of operationsTotal wait time, weeksCrude Rate, per 100SE Hazard ratio 95% CI*1991–1992 1504 23047 6.5 0.2 1.00 referent1993–1994 1646 25480 6.5 0.2 1.00 0.93, 1.081995–1996 1727 34186 5.1 0.1 0.70 0.65, 0.761997–1998 1613 30384 5.3 0.1 0.77 0.71, 0.831999–2000 1501 24029 6.2 0.2 0.94 0.88, 1.02All periods 7991 137126 5.8 0.1 - -Abbreviations: SE = standard error; CI = confidence interval*adjusted for priority group and comorbidity; stratified by age and sex**0 patients were on the wait list on December 31 2001Page 7 of 10(page number not for citation purposes)In priority group 2, the average weekly number of opera-tions per 100 patients listed varied from 7.3 (6.8–7.7) inwith CAD spent on CABG wait lists before and after theprovincial government started providing supplementaryBMC Health Services Research 2005, 5:22 http://www.biomedcentral.com/1472-6963/5/22funding to increase the annual number of CABG opera-tions. We sought to determine whether the period of reg-istration had an effect on the wait-list time and whetherthe period effect was similar across priority groups. Usingthe population-based registry, we compared the numberof weeks from registration to surgery for equal propor-tions of patients across different registration periods. Inthese comparisons, we accounted for the priority mix atregistration. We used prospective follow-up of all patientsregistered to avoid biases inherent in wait-list statisticsbased on patients undergoing the procedure only[19].We found that the registration period had an effect on theamount of time that patients spent awaiting CABG in BCin the 1990s. Wait-list times in the 1995–96 cohort weresuch that 50% and 75% patients underwent surgerywithin 15 and 26 weeks, respectively, whereas one-half ofthe 1991–92 cohort underwent surgery within nine weeksand three quarters did so within 19 weeks. This trend wasreversed later, such that the 1999–2000 patients waitedno longer than did their 1991–92 counterparts. Relativeto the 1991–92 cohort, the conditional weekly probabili-ties of undergoing surgery were 30% lower in 1995–96patients, and 23% lower in 1997–98 patients, while therewere no differences between periods 1991–92 and 1999–2000.We also found that the effect of registration period wasdifferent across priority groups. In priority group 1, thewait-list time increased by the middle of the decade andincreased even further by the end of the decade. This mayreflect changes in queuing patients with more severe CADincluding lessened concern about safety of delayingpatients with left main stenosis[20] as well as increasinguse of angioplasty to treat patients who would have for-merly been treated surgically[21]. In priority groups 2 andlist time in groups 2 and 3 decreased later, such that therewere no differences between the 1999–2000 and 1991–92cohorts.Studies examining access to elective care in Canada andelsewhere often report median or mean times [22-25]. Wefound that reporting the probability of undergoing CABGas a function of wait-list time helps overcome some limi-tations of using single-value statistics in understandingdifferences between periods [26-29]. For instance, wewere able to conclude that not only did changes in waitsreduce the median delay from 15 to 10 weeks in the1995–96 and 1999–2000 cohorts, respectively, but alsoprovided 20% compression in access for 40% patientsstaying on the lists longer than the median time. Studyingthe distributions of wait-list times, we also were able tocompare the conditional weekly probability of undergo-ing CABG across registration periods while adjusting forpriority, comorbidity, age and sex.The lack of information on hospitals or surgeons could bea limitation of this study as we were not able to adjust forthe volume of CABG between the four tertiary carehospitals where the operation was performed or for thewait lists between cardiac surgeons.ConclusionOur results provide evidence for a significant reduction inwait-list time after supplementary funding was providedon an annual basis to tertiary care hospitals within a singlepublicly funded health system. While system-level factorssuch as changes in the organization or delivery of servicesmay have affected the wait-list time, one plausible reasonfor the observed reduction was that the hospitals hadcapacity to increase the number of operations. Comparedto 1995–96, there was a 12% increase (from 3,696 toTable 5: Access to surgery by registration period and priority group for subjects registered for isolated coronary artery bypass surgery in British Columbia 1991–2000, as measured by adjusted hazard ratios*Registration periodPriority 1 Priority 2 Priority 3HR (95% CI) HR (95% CI) HR (95% CI)1991–1992 1.00 referent 1.00 referent 1.00 referent1993–1994 0.79 (0.57, 1.09) 1.10 (1.01, 1.20) 0.78 (0.65, 0.92)1995–1996 0.66 (0.50, 0.87) 0.71 (0.65, 0.78) 0.69 (0.58, 0.82)1997–1998 0.49 (0.36, 0.67) 0.82 (0.75, 0.89) 0.75 (0.63, 0.88)1999–2000 0.47 (0.33, 0.68) 0.99 (0.90, 1.08) 1.07 (0.90, 1.26)Abbreviations: HR = hazard ratio; CI = confidence interval*adjusted for priority group and comorbidity; stratified by age and sexPage 8 of 10(page number not for citation purposes)3, the wait-list time also increased by the middle of thedecade. In contrast to priority group 1, however, the wait-4,174) in the total number of CABG operations in 1999–2000, Table 6. Also, between 1995–96 and 1999–2000,BMC Health Services Research 2005, 5:22 http://www.biomedcentral.com/1472-6963/5/22there was a 13% decrease (from 54% to 41%) in the pro-portion of patients accessing the operation through waitlists, indicating that supplementary funding was used toprovide more operations without delay.The relatively short time frame following the fundingincrease is a limitation of our study. As discussed else-where, supplementary funding may not result in shorten-ing wait lists if hospitals function near full capacity [30],or, if it is expected that funding will be withdrawn afterwait lists are reduced[10]. Reducing wait lists may requireinvesting in new health services facilities. In Denmark,rates of open-heart surgery increased by 70% and themedian waiting times declined by half since 1994 whenadditional capacity for cardiac surgical care was estab-lished by increasing the number of operating theatres,equipment and personnel [30]. On-going study of wait-list times for CABG in BC will help determine the perma-nence of the impact of supplementary funding.Competing interestsThe author(s) declare that they have no competinginterests.Authors' contributionsARL conceived and designed the study, acquired the data,interpreted the results, and drafted the manuscript. BGSconceived and designed the study, analysed the data,interpreted the results, and drafted the manuscript. RHparticipated in the design of the study, helped acquire thedata, and interpreted the results. MK helped acquire thedata, and interpreted the results. JMF participated in thedesign of the study and interpreted the results. MTS partic-ipated in the design of the study and interpreted theresults. All authors read and approved the finalmanuscript.Additional materialAcknowledgementsThe authors gratefully acknowledge the contributions of the following indi-viduals: Rita Sobolyeva, Lisa Kuramoto, Laurie Kilburn, Christopher Buller, Min Gao, and Gordon Pate.The following cardiac surgeons are contributors to the BCCR Surgical Research Committee: Drs. James Abel, Richard Brownlee, Larry Burr, Anson Cheung, James Dutton, Guy Fradet, Virginia Gudas, Robert Hayden, Eric Jamieson, Michael Janusz, Shahzad Karim, Tim Latham, Jacques LeBlanc, Sam Lichtenstein, Hilton Ling, John Ofiesh, Michael Perchinsky, Peter Skars-gard and Frank TyersThis study received financial support from the: St Paul's Hospital Founda-tion (ARL), Vancouver Coastal Health Research Institute (BGS, JMF), Michael Smith Foundation for Health Research (ARL), Canada Foundation for Innovation (ARL, BGS), and Canada Research Chairs program (BGS). None of the sponsors had any role in the study design; in the collection, analysis, and interpretation of data; in the writing of the report; or the deci-sion to submit the paper for publication.References1. Siciliani L, Hurst J: Explaining Waiting Times Variations forElective Surgery across OECD Countries. Volume OECD HealthWorking Papers No. 7. Paris, Organisation for Economic Co-operationand Development; 2003. 2. Katz SJ, Mizgala HF, Welch HG: British Columbia sends patientsto Seattle for coronary artery surgery. Bypassing the queuein Canada. JAMA 1991, 266:1108-1111.3. Naylor CD, Sykora K, Jaglal SB, Jefferson S: Waiting for coronaryTable 6: Distributions of patients who were registered on wait lists or operated without delay in British Columbia 1991–2000, by registration periodRegistration Period Patients identified as needing CABGRegistered on wait lists Operated without delayN (%) N (%)1991–1992 1724 (49.3) 1770 (50.7)1993–1994 1889 (55.3) 1526 (44.7)1995–1996 2010 (54.4) 1686 (45.6)1997–1998 1888 (48.6) 1997 (51.4)1999–2000 1720 (41.2) 2454 (58.8)Additional File 1The Microsoft® Word 2002 file "BC consensus guidelines for CABG prior-ity.doc" shows the guidelines used by British Columbian cardiac surgeons for assigning priority to patients registered for coronary artery bypass grafting.Click here for file[http://www.biomedcentral.com/content/supplementary/1472-6963-5-22-S1.doc]Page 9 of 10(page number not for citation purposes)artery bypass surgery: population-based study of 8517 con-secutive patients in Ontario, Canada. The Steering Commit-Publish with BioMed Central   and  every scientist can read your work free of charge"BioMed Central will be the most significant development for disseminating the results of biomedical research in our lifetime."Sir Paul Nurse, Cancer Research UKYour research papers will be:available free of charge to the entire biomedical communitypeer reviewed and published immediately upon acceptancecited in PubMed and archived on PubMed Central BMC Health Services Research 2005, 5:22 http://www.biomedcentral.com/1472-6963/5/22tee of the Adult Cardiac Care Network of Ontario. Lancet1995, 346:1605-1609.4. Noseworthy TW, McGurran JJ, Hadorn DC: Waiting for sched-uled services in Canada: development of priority-settingscoring systems. J Eval Clin Pract 2003, 9:23-31.5. Morgan CD, Sykora K, Naylor CD: Analysis of deaths while wait-ing for cardiac surgery among 29,293 consecutive patients inOntario, Canada. The Steering Committee of the CardiacCare Network of Ontario. Heart 1998, 79:345-349.6. Naylor CD, Baigrie RS, Goldman BS, Basinski A: Assessment of pri-ority for coronary revascularisation procedures. Revascular-isation Panel and Consensus Methods Group. Lancet 1990,335:1070-1073.7. Klatt I: Understanding the Canadian health care system. Jour-nal of Financial Service Professionals 2000, 54:42-51.8. Canadian Public Policy On-line 1998, 3:.9. Sanmartin C, Shortt SE, Barer ML, Sheps S, Lewis S, McDonald PW:Waiting for medical services in Canada: lots of heat, but lit-tle light. CMAJ 2000, 162:1305-1310.10. Inersen T: A theory of hospital waiting lists. J of Health Economics1993, 12:55-71.11. Volk T, Hahn L, Hayden R, Abel J, Puterman ML, Tyers GF: Reliabil-ity audit of a regional cardiac surgery registry. J Thorac Cardio-vasc Surg 1997, 114:903-910.12. Chamberlayne R, Green B, Barer ML, Hertzman C, Lawrence WJ,Sheps SB: Creating a population-based linked health database:a new resource for health services research. Can J Public Health1998, 89:270-273.13. World Health Organization: . In International classification of diseases.Manual of the international statistical classification of diseases, injuries andcauses of death. 9th edition. Geneva, Switzerland, World HealthOrganization; 1977. 14. Humphries KH, Rankin JM, Carere RG, Buller CE, Kiely FM, SpinelliJJ: Co-morbidity data in outcomes research: are clinical dataderived from administrative databases a reliable alternativeto chart review? J Clin Epidemiol 2000, 53:343-349.15. Stemmer EA, Aronow WS: Surgical management of coronaryarterial disease in the elderly. Coron Artery Dis 1998, 9:279-290.16. Hosmer DW, Lemeshaw S: In Applied Survival Analysis: regres-sion modeling time to event data. New York: Wiley & Son;1998:27-86. 17. Klein JP, Moeschberger ML: Hypothesis testing. In Survival analysis:techniques for censored and truncated data New York, Springer;1997:191-201. 18. Cox DR: Regression models and life tables. J R Stat Soc B 1972,34:387-404.19. Armstrong PW: First steps in analysing NHS waiting times:avoiding the 'stationary and closed population' fallacy. StatMed 2000, 19:2037-2051.20. Maziak DE, Rao V, Christakis GT, Buth KJ, Sever J, Fremes SE, Gold-man BS: Can patients with left main stenosis wait for coronaryartery bypass grafting? Ann Thorac Surg 1996, 61:552-557.21. Faris PD, Grant FC, Galbraith PD, Gong Y, Ghali WA: Diagnosticcardiac catheterization and revascularization rates for coro-nary heart disease. Can J Cardiol 2004, 20:391-397.22. Fox GA, O'Dea J, Parfrey PS: Coronary artery bypass graft sur-gery in Newfoundland and Labrador. CMAJ 1998,158:1137-1142.23. Naylor CD, Morgan CD, Levinton CM, Wheeler S, Hunter L,Klymciw K, Baigrie RS, Goldman BS: Waiting for coronary revas-cularization in Toronto: 2 years' experience with a regionalreferral office. CMAJ 1993, 149:955-962.24. Bernstein SJ, Rigter H, Brorsson B, Hilborne LH, Leape LL, Meijler AP,Scholma JK, Nord AS: Waiting for coronary revascularization:a comparison between New York State, The Netherlandsand Sweden. Health Policy 1997, 42:15-27.25. Pell JP, Pell AC, Norrie J, Ford I, Cobbe SM: Effect of socioeco-nomic deprivation on waiting time for cardiac surgery: ret-rospective cohort study. BMJ 2000, 320:15-18.26. Torkki M, Linna M, Seitsalo S, Paavolainen P: How to report andmonitor the performance of waiting list management. Int JTechnol Assess Health Care 2002, 18:611-618.27. Cromwell DA, Griffiths DA: Waiting time information services:how well do different statistics forecast a patient's wait? Aust28. Mayo NE, Scott SC, Shen N, Hanley J, Goldberg MS, MacDonald N:Waiting time for breast cancer surgery in Quebec. CMAJ 2001,164:1133-1138.29. Sobolev B, Brown P, Zelt D: Variation in time spent on the wait-ing list for elective vascular surgery: a case study. Clin InvestMed 2000, 23:227-238.30. Hurst J, Siciliani L: Tackling excessive waiting times for electivesurgery: a comparison of policies in twelve OECD countries.Paris, Organisation for Economic Co-operation and Development;2003. Pre-publication historyThe pre-publication history for this paper can be accessedhere:http://www.biomedcentral.com/1472-6963/5/22/prepubyours — you keep the copyrightSubmit your manuscript here:http://www.biomedcentral.com/info/publishing_adv.aspBioMedcentralPage 10 of 10(page number not for citation purposes)Health Rev 2002, 25:75-85.


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