We sought to determine whether more comprehensive risk-adjustment models have a significant impact on hospital risk-adjusted mortality rates after coronary artery bypass graft surgery (CABG) in Ontario, Canada.
The Working Group Panel on the Collaborative CABG Database Project has categorized 44 clinical variables into 7 core, 13 level 1 and 24 level 2 variables, to reflect their relative importance in determining short-term mortality after CABG.
Using clinical data for all 5,517 patients undergoing isolated CABG in Ontario in 1993, we developed 12 increasingly comprehensive risk-adjustment models using logistic regression analysis of 6 of the Panel's core variables and 6 of the Panel's level 1 variables. We studied how the risk-adjusted mortality rates of the nine cardiac surgery hospitals in Ontario changed as more variables were included in these models.
Incorporating six of the core variables in a risk-adjustment model led to a model with an area under the receiver operating characteristic (ROC) curve of 0.77. The ROC curve area slightly improved to 0.79 with the inclusion of six additional level 1 variables (p = 0.063). Hospital risk-adjusted mortality rates and relative rankings stabilized after adjusting for six core variables. Adding an additional six level 1 variables to a risk-adjustment model had minimal impact on overall results.
A small number of core variables appear to be sufficient for fairly comparing risk-adjusted mortality rates after CABG across hospitals in Ontario. For efficient interprovider comparisons, risk-adjustment models for CABG could be simplified so that only essential variables are included in these models.
The objective of this study was to compare the classification of hospitals as outcomes outliers using a commonly implemented frequentist statistical approach vs. an implementation of Bayesian hierarchical statistical models, using 30-day hospital-level mortality rates for a cohort of acute myocardial infarction patients as a test case. For the frequentist approach, a logistic regression model was constructed to predict mortality. For each hospital, a risk-adj usted mortality rate was computed. Those hospitals whose 95% confidence interval, around the risk-adjusted mortality rate, excludes the mean mortality rate were classified as outliers. With the Bayesian hierarchical models, three factors could vary: the profile of the typical patient (low, medium or high risk), the extent to which the mortality rate for the typical patient departed from average, and the probability that the mortality rate was indeed different by the specified amount. The agreement between the two methods was compared for different patient profiles, threshold differences from the average and probabilities. Only marginal agreement was shown between the Bayesian and frequentist approaches. In only five of the 27 comparisons was the kappa statistic at least 0.40. The remaining 22 comparisons demonstrated only marginal agreement between the two methods. Within the Bayesian framework, hospital classification clearly depended on patient profile, threshold and probability of exceeding the threshold. These inconsistencies raise questions about the validity of current methods for classifying hospital performance, and suggest a need for urgent research into which methods are most meaningful to clinicians, managers and the general public.
This study was conducted to assess the overall mortality rate and the amount of interhospital variation in risk-adjusted mortality rates after coronary artery bypass graft (CABG) surgery in Ontario, Canada. CABG outcomes data are not publicly disseminated in Ontario.
Clinical risk factors and surgical outcomes were collected on 15,608 patients undergoing isolated CABG surgery between April 1, 1991, and March 31, 1994, at the nine hospitals performing adult cardiac surgery in Ontario. The data were analyzed on the basis of a fiscal year. The overall mortality rate was 3.01%, and the risk-adjusted mortality rate declined from 3.17% in 1991 to 2.93% in 1993. In 1991, one of the nine hospitals had a risk-adjusted mortality rate significantly lower than the provincial average. Otherwise, the hospitals all had risk-adjusted mortality rates within the expected range during the time period of the study. All hospitals performed > 300 CABG procedures in 1992 and 1993, and only 2 of 42 cardiac surgeons performed
This study examined the relationship between gender and in-hospital mortality using data from patients undergoing coronary artery bypass surgery (CABS) in the province of Ontario. All patients who underwent CABS between April 1, 1991 and March 31, 1992 at the 9 cardiac surgery institutions were included for study (n = 5,175). The unadjusted in-hospital mortality rate was 3.3% and was higher among females (5.3%) than males (2.8%). Using logistic regression analysis to adjust for several predictors of in-hospital mortality the odds ratio estimate (OR) for female sex was 1.55 and was statistically significant (95% confidence interval (CI) 1.09 to 2.20). Women experienced rates of in-hospital mortality that are 1.6 times greater than males following bypass surgery after case-mix adjustment for age, anatomical disease severity, anginal class, and comorbid conditions. Severe unstable angina had the greatest potential contribution to in-hospital mortality (OR = 7.51, 95% CI = 3.71-15.23) and was more prevalent in women, indicating that excess mortality may be due to delayed diagnosis in women.
To determine, for abdominal aortic aneurysm surgery, whether a previously reported relationship between hospital case volume and mortality rate was observed in Ontario hospitals and to assess the potential impact of age on the mortality rate for elective surgery.
Population based observational study using administrative data.
All Ontario hospitals where repair of abdominal aortic aneurysm as a primary procedure was performed during 1988-92.
These comprised 5492 patients with unruptured abdominal aortic aneurysms and 1203 patients with ruptured abdominal aortic aneurysms admitted to hospital between 1988-92 for repair of abdominal aortic aneurysm as a primary procedure.
In-hospital death and length of in-hospital stay.
The case fatality rate was 3.8% for unruptured abdominal aortic aneurysms and 40.0% for ruptured abdominal aortic aneurysms. For unruptured cases, after adjustment for patient and hospital covariates, each 10 case per year increase in hospital volume was related to a 6% reduction in relative odds of death (odds ratio (OR) 0.94, 95% confidence intervals 0.88, 0.99) and 0.29 days reduction (95% CI -0.22, -0.35) in postoperative in-hospital stay. Female sex (OR 1.53, 95% CI 1.08, 2.18) and transfer from another acute care hospital (OR 4.37, 95% CI 2.62, 7.29) were associated with increased case fatality rates among patients in the unruptured category. For ruptured cases, neither the case fatality rate nor postoperative in-hospital stay were significantly related to hospital volume. The case fatality rates increased linearly and substantially with advancing age both for unruptured and ruptured aneurysms, and the excess risk of postoperative death in ruptured as compared to unruptured aneurysms was substantially higher in older patients.
The relationship between hospital volume and mortality or morbidity was very modest and observed only for elective surgery. Case fatality rates in patients with ruptured abdominal aortic aneurysms remained 10 times higher than for patients with unruptured abdominal aortic aneurysms, despite improvements in overall mortality in comparison to previously published data. More effective detection of aneurysms, including elective repair for those once considered "high risk" older patients, might further reduce the toll from ruptured aortic aneurysms.
Many studies have found that patients with acute myocardial infarction (AMI) who are admitted to hospitals with on-site revascularization facilities have higher rates of invasive cardiac procedures and better outcomes than patients in hospitals without such facilities. Whether such differences are due to invasive procedure rates alone or to other patient, physician, and hospital characteristics is unknown.
To determine whether invasive procedural rate variations alone account for outcome differences in patients with AMI admitted to hospitals with or without on-site revascularization facilities.
Retrospective, observational cohort study using linked population-based administrative data from a universal health insurance system.
One hundred ninety acute care hospitals in Ontario, 9 of which offered invasive procedures.
A total of 25 697 patients hospitalized with AMI between April 1, 1992, and December 31, 1993, of whom 2832 (11%) were in invasive hospitals.
Mortality, recurrent cardiac hospitalizations, and emergency department visits in the 5 years following the index admission, adjusted for patient age, sex, socioeconomic status, illness severity, and index revascularization procedures; attending physician specialty; and hospital volume, teaching status, and geographical proximity to invasive-procedure centers and compared by hospital type.
Patients admitted to invasive-procedure hospitals were much more likely to undergo revascularization (11.4% vs 3.2% at other hospitals; P
This study attempted to determine population-based trends in in-hospital patient fatality from acute myocardial infarction.
The in-hospital prognosis for patients with acute myocardial infarction should be improving as a result of adoption of treatments proved in randomized trials (e.g., thrombolytic, beta-adrenergic blocking and anticoagulant agents and aspirin). However, all trials are subject to selection biases, eligibility is limited for some therapies, and proved therapies may be underused even among eligible patients.
Using administrative data from all general hospitals in Ontario, Canada, we analyzed 17,489, 17,839, 18,393, 18,794, 18,716 and 19,748 records of patients with a primary discharge diagnosis of myocardial infarction for fiscal years 1981, 1983, 1985, 1987, 1989 and 1991, respectively.
After age and gender adjustment, the overall relative reduction in in-hospital case fatality rates for the 10-year period was 26.9% (99% confidence interval [CI] 26.8% to 26.9%), corresponding to an absolute reduction of 6% (99% CI 5.6% to 6.4%). Age- and gender-standardized case fatality rate decreased from 22.3% in 1981 to 21.4% in 1985, followed by a highly significant decline to 16.3% in 1991. On the basis of the relation of comparative mortality to days of hospital stay, declining mortality was not an artifact of decreasing length of stay.
There have been encouraging improvements in survival after acute myocardial infarction over the past 6 years. Further improvements may require development of new therapies that can be more widely applied to this patient population.
To determine whether sex differences exist in the use of coronary angiography, coronary artery bypass surgery (CABS) or percutaneous transluminal coronary angioplasty (PTCA) among persons recently diagnosed with an acute myocardial infarction (AMI) in Canada.
A growing body of literature suggests that coronary artery disease in males is treated differently from females. Specifically, recent studies have indicated that sex may influence decisions about the use of invasive diagnostic and therapeutic coronary procedures in patients with suspected or proven coronary artery disease.
The study design is a population-based inception cohort study. The data source is hospital discharges from all acute care hospitals in Ontario. The study population consisted of 6949 men and women discharged with a principal diagnosis of AMI between April 1 and September 30, 1990, and followed through record linkage until March 31, 1991 to determine whether any invasive coronary procedures were performed after their AMI. Odds ratio estimates (OR) and 95% confidence intervals (95% CI) for use of coronary angiography, CABS and PTCA in men were compared with those in women.
The adjusted OR for coronary angiography was 1.4 (95% CI 1.2 to 1.6), indicating that males were more likely to undergo angiography than females. A similar finding was seen for CABS (OR = 1.6, 95% CI 1.2 to 2.1), but for PTCA, the sex difference was less pronounced (OR = 1.3, 95% CI 1.0 to 1.7). Cox proportional hazards regression also was used to test the hypothesis and showed similar results.
Women suffering AMI undergo coronary angiography and CABS at a significantly lower rate than men in Ontario, with similar trends evident in use of PTCA.
Unexplained variation in length of stay (LOS) following acute myocardial infarction (AMI) has been observed among American hospitals. We explored this phenomenon in the universal hospital care system of Ontario, Canada's largest province, analyzing general hospital discharge abstracts for all patients with a primary diagnosis of AMI. Case homogeneity was increased by excluding inter-hospital transfers, in-hospital deaths, patients with revascularization during the index admission and patients with severe comorbid conditions. This left 11,411 records of patients in 187 hospitals from April 1, 1990 to March 31, 1991. The mean length of stay was 9.9 days with standard deviation of 3.8. Available patient and hospital characteristics explained only 12% of the individual variation in LOS. Interinstitutional variation remained highly significant after controlling for patients' characteristics within the 87 hospitals admitting more than 50 cases per annum; these hospitals accounted for 84% of the eligible provincial admissions. The grand mean length of stay for 87 hospitals was 10 days, ranging from 6.6 to 12.9 days. Stepwise multiple linear regression analyses showed that lower caseload was associated with an increased length of hospitalization. Thus, despite Ontario's uniform system of hospital funding and medical insurance, a large amount of unexplained variation in length of stay exists for patients hospitalized with AMI, affecting thousands of bed-days per annum.