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Peter C Austin

Publications and source records attributed to Peter C Austin.

At least 73 records · Page 4Linked to original sources
PubMed2003

Sex differences in carotid endarterectomy outcomes: results from the Ontario Carotid Endarterectomy Registry.

BACKGROUND AND PURPOSE: The existing literature provides conflicting evidence on surgical risks of carotid endarterectomy in women compared with men. We used data from a large population-based carotid surgery registry to determine whether sex differences exist in the risk of perioperative complications from carotid endarterectomy. METHODS: We analyzed data from the Ontario Carotid Endarterectomy Registry, which contains data on all patients who underwent carotid endarterectomy in the province of Ontario between 1994 and 1997. We compared the risk of death or stroke at 30 days in women and men and used multivariate analyses to adjust for age, comorbid conditions, and surgical factors. Secondary analyses compared the risks of death and/or stroke in women and men at 2 years after surgery. RESULTS: The study sample consisted of 6038 patients (35% women). The risks of perioperative stroke or death were not significantly different in women compared with men (adjusted hazard ratio, 1.10; 95% CI, 0.90 to 1.35). The combined risk of stroke or death at 2 years after surgery was also similar in women and men (adjusted hazard ratio, 1.05; 95% CI, 0.92 to 1.21). However, women were more likely to have a stroke (adjusted hazard ratio, 1.26; 95% CI, 1.05 to 1.51) and less likely to die (adjusted hazard ratio, 0.82; 95% CI, 0.68 to 0.99) within 2 years after surgery. CONCLUSIONS: Perioperative complication rates from carotid endarterectomy are similar in women and men. Women should not be discouraged from carotid endarterectomy solely on the basis of surgical risks.

Adult↗
PubMed2003

Effect of selective cyclooxygenase 2 inhibitors and naproxen on short-term risk of acute myocardial infarction in the elderly.

BACKGROUND: Recent debate has emerged regarding the cardiovascular safety of selective cyclooxygenase 2 inhibitors and the possible cardioprotective effect of naproxen sodium. We compared the rates of acute myocardial infarction (AMI) among elderly patients dispensed selective cyclooxygenase 2 inhibitors, naproxen, and nonselective nonnaproxen nonsteroidal anti-inflammatory drugs (NSAIDs). METHODS: We conducted a population-based retrospective cohort study using administrative health care data from Ontario, Canada, from April 1, 1998, to March 31, 2001. We identified NSAID-naive cohorts of subjects aged 66 years and older in whom treatment was initiated with celecoxib (n = 15 271), rofecoxib (n = 12 156), naproxen (n = 5669), and nonnaproxen nonselective NSAIDs (n = 33 868), along with a randomly selected control cohort not exposed to NSAIDs (n = 100 000). Multivariate Cox proportional hazards models were used to compare AMI rates between study drug groups while controlling for potential confounders. RESULTS: Relative to control subjects, the multivariate model showed no significant differences in AMI risk for new users of celecoxib (adjusted rate ratio [aRR], 0.9; 95% confidence interval [CI], 0.7-1.2), rofecoxib (aRR, 1.0; 95% CI, 0.8-1.4), naproxen (aRR, 1.0; 95% CI, 0.6-1.7), or nonnaproxen nonselective NSAIDs (aRR, 1.2; 95% CI, 0.9-1.4). CONCLUSIONS: The findings of this observational study suggest no increase in the short-term risk of AMI among users of selective cyclooxygenase 2 inhibitors as commonly used in clinical practice. Furthermore, the findings do not support a short-term reduced risk of AMI with naproxen.

Aged↗
PubMed2003

Geography and service supply do not explain socioeconomic gradients in angiography use after acute myocardial infarction.

BACKGROUND: Socioeconomic status appears to be an important predictor of coronary angiography use after acute myocardial infarction. One potential explanation for this is that patients with lower socioeconomic status live in neighbourhoods near nonteaching hospitals that have no catheterization capacity, few specialists and lower volumes of patients with acute myocardial infarction. This study was conducted to determine whether the impact of socioeconomic status on angiography use would be lessened by considering variations in the supply of services. METHODS: We examined payment claims for physician services, hospital discharge abstracts and vital status data for 47 036 patients with acute myocardial infarction admitted to hospitals in Ontario between April 1994 and March 1997. Neighbourhood income of each patient was obtained from Canada's 1996 census. Using multivariate hierarchical logistic regression and adjusting for baseline patient and physician factors, we examined the interaction among hospital and regional characteristics, socioeconomic status and angiography use in the first 90 days after admission to hospital for acute myocardial infarction. RESULTS: Within each hospital and geographic subgroup, crude rates of angiography rose progressively with increases in neighbourhood income. After adjusting for sociodemographic, clinical and physician characteristics, hospitals with on-site angiography capacity (adjusted odds ratio [OR] 1.88, 95% confidence interval [CI] 1.52-2.33), those with university affiliations (adjusted OR 1.60, 95% CI 1.27-2.01) and those closest to tertiary institutions (adjusted OR 1.57, 95% CI 1.32-1.87) were all associated with higher 90-day angiography use after acute myocardial infarction. However, the relative impact of socioeconomic status on 90-day angiography use was similar whether or not hospitals had on-site procedural capacity (interaction term p = 0.68), had university affiliations (interaction term p = 0.99), were near tertiary facilities (interaction term p = 0.67) or were in rural or urban regions (interaction term p = 0.90). INTERPRETATION: Socioeconomic status was as important a predictor of angiography use in hospitals with ready access to cardiac catheterization facilities as it was in those without. The socioeconomic gradient in the use of angiography after acute myocardial infarction cannot be explained by the distribution of specialists or tertiary hospitals.

Cardiac Care Facilities↗
PubMed2003

Meta-analysis of the effects of endothelin receptor blockade on survival in experimental heart failure.

BACKGROUND: Although an initial study of endothelin receptor blockade reported positive findings, subsequent experiments and clinical trials in humans found little or no benefit. METHODS: We applied meta-analytic methods to assess the methodologic rigor of preclinical studies of endothelin blockade and to quantitatively evaluate the totality of evidence regarding the effect of endothelin receptor blockers in experimental heart failure. A total of 396 animals were assigned to control and 594 were assigned to experimental therapy in the pooled analysis. Of the 9 studies identified, no study reported a priori sample size justification. Although there was a tendency to increased mortality with early administration (relative risk 1.39, P=.15) and decreased mortality with late administration (relative risk 0.85, P=.6), in the overall analysis, there was no significant evidence of benefit or harm (relative risk 1.03, P=.9). Studies with a small sample size had estimated effects that tended to deviate further from the pooled estimate of all studies. CONCLUSIONS: Consideration of mortality effects in the totality of studies revealed no significant effect of endothelin antagonists in animal models of experimental heart failure. Given the potential for between-study variability, reliance on studies with small sample size may lead to unrealistic expectations when extrapolating preclinical experimental results to future research.

Animals↗
PubMed2003

Comparing hierarchical modeling with traditional logistic regression analysis among patients hospitalized with acute myocardial infarction: should we be analyzing cardiovascular outcomes data differently?

BACKGROUND: Data in health research are frequently structured hierarchically. For example, data may consist of patients treated by physicians who in turn practice in hospitals. Traditional statistical techniques ignore the possible correlation of outcomes within a given practice or hospital. Furthermore, imputing characteristics measured at higher levels of the hierarchy to the patient-level artificially inflates the amount of available information on the effect of higher-level characteristics on outcomes. METHODS: Conventional logistic regression models and multilevel logistic regression models were fit to a cross-sectional cohort of patients hospitalized with a diagnosis of acute myocardial infarction. The statistical significance of the effect of patient, physician, and hospital characteristics on patient outcomes was compared between the 2 modeling strategies. RESULTS: The 2 analytic strategies agreed well on the effect of patient characteristics on outcomes. According to the traditional analysis, teaching status was statistically significantly associated with 5 of the 9 outcomes, whereas the multilevel models did not find a statistically significant association between teaching status and any patient outcomes. Similarly, the traditional and multilevel models disagreed on the statistical significance of the effect of being treated at a revascularization hospital and 3 patient outcomes. CONCLUSIONS: In comparing the resultant models, we see that false inferences can be drawn by ignoring the structure of the data. Conventional logistic regression tended to increase the statistical significance for the effects of variables measured at the hospital-level compared to the level of significance indicated by the multilevel model.

Adult↗
PubMed2003

Patient, physician, and community factors affecting referrals to specialists in Ontario, Canada: a population-based, multi-level modelling approach.

QUESTION ADDRESSED: This population-based study examines the factors affecting referrals by primary care physicians (PCPs) to specialists. MATERIALS AND METHODS: Multilevel Poisson models were used to test the impact of patient, physician and community-level variables on the referral rate (the number of office-based specialist referrals per patient by the patient's customary PCP in fiscal year 1997/98). Patients from each of 6972 PCPs with sufficient data in Ontario were examined. RESULTS: The average patient had 0.56 referrals per year (range 0-61). Referrals were higher at ages 1 and 77 to 78, and among women of childbearing age. Chronic disease variables were strongly correlated with referral rates. Patients in poor neighborhoods had more referrals, because they had more chronic diseases. After controlling for disease, individuals in the top 9% wealthiest neighborhoods had 4% more referrals. Female physicians made 8% more referrals than men. Older physicians referred more because they saw older patients; after controlling for patient age, physician age had no effect. Referrals were 14% higher in cities with medical schools compared with other cities and 12% lower in small towns. However, local specialist supply was unrelated to referral rates. CONCLUSION: This study improves our understanding of the impact of physician gender and age on referrals. It suggests that community type, not specialist supply, predicts variations in referrals. Lastly, it identifies preferential access to specialists among high-income earners, even within Canada's universal health insurance system. However, this effect is modest, suggesting that the system does provide reasonably equitable access to referrals.

Adolescent↗
PubMed2003

Quantile regression: a statistical tool for out-of-hospital research.

The performance of out-of-hospital systems is frequently evaluated based on the times taken to respond to emergency requests and to transport patients to hospital. The 90th percentile is a common statistic used to measure these indicators, since they reflect performance for most patients. Traditional regression models, which assess how the mean of a distribution varies with changes in patient or system characteristics, are thus of limited use to researchers in out-of-hospital care. In contrast, quantile regression models estimate how specified quantiles (or percentiles) of the distribution of the outcome variable vary with patient or system characteristics. The authors examined the performance of traditional linear regression vs. that of quantile regression to assess the association between hospital transport interval and patient and system characteristics. They demonstrate that richer inferences can be drawn from the data using quantile regression, utilizing data drawn from a study of ambulance diversion and out-of-hospital delay. The results demonstrate that the effect of ambulance diversion upon out-of-hospital transport intervals is not uniform, but is worse on the right tail of the distribution of transport intervals. In other words, ambulance diversion disproportionately affects those patients who already have longer transport intervals. Second, the distribution of transport intervals, conditional on a given set of variables, is positively skewed, and not uniformly or symmetrically distributed. The flexibility of quantile regression models makes them particularly well suited to out-of-hospital research, and they may allow for more relevant evaluation of out-of-hospital system performance.

Ambulances↗
PubMed2003

Anxiety-related visits to Ontario physicians following September 11, 2001.

OBJECTIVE: To determine whether the climate of increased anxiety following the terrorist attacks of September 11, 2001, and the subsequent anthrax cases led to increased anxiety-related physician visits. METHOD: We undertook a retrospective, population-based study of all Ontario residents. We identified physician visits using Ontario's universal health care insurance program. Interventional autoregressive integrated moving average (ARIMA) time series models were used to examine the impact of the terrorist attacks and anthrax infections on the rate of anxiety-related physician visits. RESULTS: Neither the terrorist attacks of September 11 (P > or = 0.40) nor the anthrax infections in October and November (P > or = 0.14) had a statistically significant impact on the rate of anxiety-related visits to physicians. CONCLUSIONS: The climate of heightened anxiety did not result in increased demand for mental health services.

Anxiety Disorders↗
PubMed2003

Processes and outcomes of care for diabetic acute myocardial infarction patients in Ontario: do physicians undertreat?

OBJECTIVE: To compare the health service utilization and long-term outcomes of acute myocardial infarction (AMI) patients with and without diabetes in Ontario. RESEARCH DESIGN AND METHODS: We examined 25,697 patients from Ontario (6,052 and 19,645 patients with and without diabetes, respectively) who were hospitalized because of AMI between 1 April 1992 and 31 December 1993. Using linked administrative databases, we determined the use of invasive cardiac procedures at 1 year as well as the intensity of specialty follow-up care and use of evidence-based pharmacotherapies (among elderly individuals) within the first 90 days of hospital discharge. Outcomes examined included mortality and recurrent cardiac admissions at 30 days and 5 years post AMI. Multivariable analyses adjusted for sociodemographic and case-mix characteristics, attending physician specialty, and admitting hospital characteristics. RESULTS: Despite being at significantly higher risk for death at baseline, diabetic patients were less likely to be followed-up by a cardiologist (22.2 vs. 25.6%, P < 0.001), to receive myocardial revascularization (12.6 vs. 14.9%, P < 0.001), to receive beta-blockers (34.2 vs. 44.0%, P < 0.001), and to receive aspirin therapy (59.7 vs. 63.5%, P < 0.001) after AMI than their nondiabetic counterparts. Diabetes was an important independent predictor of 5-year morbidity (adjusted hazard ratio 1.52, 95% CI 1.45-1.59) and 5-year mortality outcomes (1.57, 1.50-1.63). Variations in processes of care were marginally associated with higher nonfatal complication rates for diabetic patients. CONCLUSIONS: When managing AMI patients with diabetes in Ontario, physician treatment aggressiveness does not correspond appropriately to the baseline risk of patients.

Aged↗
PubMed2003

Outcomes of acute myocardial infarction in Canada.

BACKGROUND: Little information is available on recent population-based trends in the outcomes of patients who have had an acute myocardial infarction (AMI) in Canada. METHODS: Data were analyzed from the Discharge Abstract Database and Hospital Morbidity Database of the Canadian Institute for Health Information. All new cases of AMI in Canada between fiscal 1997/98 and fiscal 1999/2000 of patients at least 20 years old were examined. Data were also analyzed from these databases for hospital readmissions for a second AMI, angina and congestive heart failure (CHF). RESULTS: There were 139,523 new AMI cases. The overall crude in-hospital AMI mortality rate in Canada was 12.3%. In-hospital mortality rate after an AMI was worse for women than for men in Canada (16.7% and 9.9%, respectively). The age- and sex-standardized in-hospital mortality rate varied from a low of 10.5% (95% CI 8.4% to 12.6%) in Prince Edward Island to a high of 13.1% (95% CI 12.8% to 13.5%) in Quebec. Among AMI survivors, 12.5% were readmitted within one year for angina, 7.7% for a second AMI and 7.5% for CHF. There were wide interregional differences in age- and sex-standardized mortality rates and one-year readmission rates. CONCLUSIONS: AMI is associated with a substantial acute mortality rate in Canada, especially in the elderly and female patients. Identifying the causes of interregional differences in patient outcomes should be a priority for future research.

Adult↗
PubMed2002

Observational study of upper gastrointestinal haemorrhage in elderly patients given selective cyclo-oxygenase-2 inhibitors or conventional non-steroidal anti-inflammatory drugs.

OBJECTIVE: To compare rates of upper gastrointestinal haemorrhage among elderly patients given selective cyclo-oxygenase-2 (COX 2) inhibitors and non-selective non-steroidal anti-inflammatory drugs (NSAIDs). DESIGN: Observational cohort study. SETTING: Administrative data from Ontario, Canada, used from 17 April 2000 to 31 March 2001 to identify population based, NSAID-naive cohorts of patients. PATIENTS: Subjects aged > or =66 years who started taking non-selective NSAIDs (n=5391), diclofenac plus misoprostol (n=5087), rofecoxib (n=14 583), or celecoxib (n=18 908) and a randomly selected control cohort not exposed to NSAIDs (n=100 000). MAIN OUTCOME MEASURES: Rate ratios of hospital admission for upper gastrointestinal haemorrhage in each drug cohort with adjustment for potential confounders. RESULTS: Relative to controls, the multivariate model revealed an increased short term risk of upper gastrointestinal haemorrhage for users of non-selective NSAIDs (adjusted rate ratio 4.0 (95% confidence intervals 2.3 to 6.9)), diclofenac plus misoprostol (3.0 (1.7 to 5.6)), and rofecoxib (1.9 (1.3 to 2.8)) but not celecoxib (1.0 (0.7 to 1.6)). Relative to celecoxib, significantly higher risks of upper gastrointestinal haemorrhage were observed for non-selective NSAIDs (4.4 (2.3 to 8.5)), diclofenac plus misoprostol (3.2 (1.6 to 6.5)), and rofecoxib (1.9 (1.2 to 2.8)). Relative to rofecoxib, non-selective NSAID users were at significantly higher risk of upper gastrointestinal haemorrhage (1.9 (1.0 to 3.5)). CONCLUSIONS: This population based observational study found a lower short term risk of upper gastrointestinal haemorrhage for selective COX-2 inhibitors compared with non-selective NSAIDs.

Aged↗
PubMed2002

Bayeswatch: an overview of Bayesian statistics.

Increasingly, clinical research is evaluated on the quality of its statistical analysis. Traditionally, statistical analyses in clinical research have been carried out from a 'frequentist' perspective. The presence of an alternative paradigm - the Bayesian paradigm - has been relatively unknown in clinical research until recently. There is currently a growing interest in the use of Bayesian statistics in health care research. This is due both to a growing realization of the limitations of frequentist methods and to the ability of Bayesian methods explicitly to incorporate prior expert knowledge and belief into the analyses. This is in contrast to frequentist methods, where prior experience and beliefs tend to be incorporated into the analyses in an ad hoc fashion. This paper outlines the frequentist and Bayesian paradigms. Acute myocardial infarction mortality data are then analysed from both a Bayesian and a frequentist perspective. In some analyses, the two methods are seen to produce comparable results; in others, they produce different results. It is noted that in this example, there are clinically relevant questions that are more easily addressed from a Bayesian perspective. Finally, areas in clinical research where Bayesian ideas are increasingly common are highlighted.

Bayes Theorem↗
PubMed2002

Effect of discharge summary availability during post-discharge visits on hospital readmission.

OBJECTIVE: To determine if the delivery of hospital discharge summaries to follow-up physicians decreases the risk of hospital readmission. SUBJECTS: Eight hundred eighty-eight patients discharged from a single hospital following treatment for an acute medical illness. SETTING: Teaching hospital in a universal health-care system. DESIGN: We determined the date that each patient's discharge summary was printed and the physicians to whom it was sent. Summary receipt was confirmed by survey and phoning each physician's office. Each patient's hospital chart was reviewed to determine their acute and chronic medical conditions as well as their course in hospital. Using population-based administrative databases, all post-hospitalization visits were identified. For each of these visits, we determined whether the summary was available. MAIN OUTCOME MEASURES: Time to nonelective hospital readmission during 3 months following discharge. RESULTS: The discharge summary was available for only 568 of 4,639 outpatient visits (12.2%). Overall, 240 (27.0%) of patients were urgently readmitted to hospital. After adjusting for significant patient and hospitalization factors, we found a trend toward a decreased risk of readmission for patients who were seen in follow-up by a physician who had received a summary (relative risk 0.74, 95% confidence interval 0.50 to 1.11). CONCLUSIONS: The risk of rehospitalization may decrease when patients are assessed following discharge by physicians who have received the discharge summary. Further research is required to determine if better continuity of patient information improves patient outcomes.

Access to Information↗
PubMed2002

A multicenter study of the coding accuracy of hospital discharge administrative data for patients admitted to cardiac care units in Ontario.

BACKGROUND: Cardiac health services researchers frequently use cohorts derived from administrative hospital discharge abstract data to study the outcomes and treatment of coronary artery disease. However, relatively limited data exist on the accuracy of the coding of cardiac diagnoses in discharge abstract data. The goal of this study was to examine the accuracy of the coding of acute myocardial infarction and other cardiac diagnoses in the Canadian Institute of Health Information hospital discharge abstracts. METHODS: Patients admitted to 58 cardiac care units (CCUs) in Ontario that participated in the Fastrak II Acute Coronary Syndromes registry were linked to CIHI hospital discharge abstracts. The most responsible diagnosis at hospital discharge in the administrative data was compared with the CCU discharge diagnosis in the clinical registry. RESULTS: A total of 58,816 CCU patients were linked to hospital discharge abstract data. The specificity, sensitivity, and positive predictive value of a most responsible diagnosis of acute myocardial infarction were 92.8%, 88.8%, and 88.5%, respectively. The specificity of CIHI diagnosis codes for arrhythmia, congestive heart failure, unstable angina, and chest pain not yet diagnosed were all at least 93.9%. However, the sensitivity of these CIHI diagnosis codes was no greater than 60.7%. Furthermore, the positive predictive values were no larger than 80.8%. CONCLUSION: Myocardial infarction is generally accurately coded in Ontario hospital discharge abstract data. However, other cardiac diagnoses are less reliably coded in discharge abstract data.

Aged↗
PubMed2002

A brief note on overlapping confidence intervals.

Clinical researchers frequently assess the statistical significance of the difference between two means by examining whether the two 95% confidence intervals overlap. The purpose of this brief communication is to illustrate that the 95% confidence intervals for two means can overlap and yet the two means can be statistically significantly different from one another at the alpha = 0.05 level.

Confidence Intervals↗
PubMed2002

Factoring socioeconomic status into cardiac performance profiling for hospitals: does it matter?

BACKGROUND: Critics of "scorecard medicine" often highlight the incompleteness of risk-adjustment methods used when accounting for baseline patient differences. Although socioeconomic status is a highly important determinant of adverse outcome for patients admitted to the hospital with acute myocardial infarction, it has not been used in most risk-adjustment models for cardiovascular report cards. OBJECTIVES: To determine the incremental impact of socioeconomic status adjustments on age, sex, and illness severity for hospital-specific 30-day mortality rates after acute myocardial infarction. METHODS: The authors compared the absolute and relative hospital-specific 30-day acute myocardial infarction mortality rates in 169 hospitals throughout Ontario between April 1, 1994 and March 31, 1997. Patient socioeconomic status was characterized by median neighborhood income using postal codes and 1996 Canadian census data. They examined two risk-adjustment models: the first adjusted for age, sex, and illness severity (standard), whereas the second adjusted for age, sex, illness severity, and median neighborhood income level (socioeconomic status). RESULTS: There was an extremely strong correlation between 'standard' and 'socioeconomic status' risk-adjusted mortality rates (r = 0.99). Absolute differences in 30-day risk-adjusted mortality rates between the socioeconomic status and standard risk-adjustment models were small (median, 0.1%; 25th-75th percentile, 0.1-0.2). The agreement in the quintile rankings of hospitals between the socioeconomic status and standard risk-adjustment models was high (weighted kappa = 0.93). CONCLUSION: Despite its importance as a determinant of patient outcomes, the effect of socioeconomic status on hospital-specific mortality rates over and above standard risk-adjustment methods for acute myocardial infarction hospital profiling in Ontario was negligible.

Age Factors↗
PubMed2002

Influence of socioeconomic status on drug selection for the elderly in Canada.

OBJECTIVE: To examine the association between socioeconomic status, as indicated by neighborhood median income levels, and physician drug selection between older, less expensive generic drugs and newer, more expensive brand-name drugs for elderly patients initiating drug therapy in a universal healthcare system. METHODS: We conducted a population-based, retrospective, cross-sectional study. Using healthcare administrative databases, we assessed the medication profiles of 128 314 patients from more than 1.4 million residents of Ontario > or =65 years old initiating antipsychotic, hydroxymethylglutaryl-coenzyme A reductase inhibitor (statin), or ocular beta-blocker drug therapy from January 1, 1998, through December 31, 1999. We examined the selection of older generic drugs relative to newer brand-name agents for patients in each of 5 income quintiles. RESULTS: Overall, brand-name drug prescribing modestly increased with increasing income quintile after adjusting for patient age and gender (61.2% in the lowest income quintile vs. 64.1% in the highest income quintile; p value for trend < 0.001). Significant risk ratios comparing the highest with the lowest income-quintile patients were observed for selection of newer, brand-name antipsychotics (RR 1.14; 95% CI 1.06 to 1.23), older generic statins (RR 0.86; 95% CI 0.77 to 0.95), and newer, brand-name ocular beta-blockers (RR 1.13; 95% CI 1.02 to 1.25). CONCLUSIONS: This study suggests that income-related differences in treatment selection by physicians may exist. The reasons for these differences and subsequent impact on health outcomes warrant further investigation.

Adrenergic beta-Antagonists↗