Extended Clopidogrel Therapy Beyond 12 Months and Long-Term Outcomes in Patients With Diabetes Mellitus Receiving Coronary Arterial Second-Generation Drug-Eluting Stents

We investigated the associations between extended clopidogrel therapy and long-term clinical outcomes in patients with diabetes mellitus (DM) after second-generation drug-eluting stent (DES) implantation. Landmark analysis was performed in 1,600 patients who received second-generation DES and were event-free at 12 months after the index procedure. The primary outcome was a composite of all-cause death or nonfatal myocardial infarction (MI) at 5 years after the index procedure. After inverse probability of treatment weighting analysis, the risk of all-cause death, or nonfatal MI was significantly lower in patients receiving clopidogrel >12 months than in those receiving clopidogrel ≤12 months in diabetic patients (13.9% vs 8.4%, hazard ratio [HR] 0.57, 95% confidence interval [CI] 0.33 to 0.99, p = 0.046). However, no significant difference was observed in all-cause death or nonfatal MI between the two groups of patients without DM (5.0% vs 8.1%, HR 1.63, 95% CI 0.90 to 2.96, p = 0.11). Extended clopidogrel therapy beyond 12 months was associated with decreased risk of all-cause death or nonfatal MI in patients with DM after second-generation DES implantation. In conclusion, our data suggest that the benefits of extended clopidogrel therapy are more prominent in diabetic patients receiving second-generation DES implantation compared with nondiabetic patients.

Impact of different nitrate therapies on long-term clinical outcomes of patients with vasospastic angina: A propensity score-matched analysis

BACKGROUND

Despite the short-term vasodilatory effects of nitrates, the prognostic effects of long-term nitrate therapy in patients with vasospastic angina (VSA) remains unclear. We investigated the prognostic impact of chronic nitrate therapy in VSA patients.

METHODS

Between January 2003 and December 2014, a total of 1154 VSA patients proven by ergonovine provocation tests were classified into nitrate (n=676) and non-nitrate (n=478) groups according to prescriptions for oral nitrates, including isosorbide mononitrate (ISMN) and nicorandil. The primary outcome was major adverse cardiovascular events (MACE), defined as a composite of cardiac death, myocardial infarction, any revascularization, or rehospitalization due to recurrent angina.

RESULTS

The nitrate group was found to have a higher risk of MACE (22.9% vs. 17.6%, hazard ratio [HR] 1.32, 95% confidence interval [CI] 1.01-1.73, p=0.043) than the non-nitrate group. After propensity score matching, the nitrate group had greater risks of MACE (HR 1.32, 95%CI 1.01-1.73, p=0.049). Patients who received the immediate-release formula of ISMN (HR 1.80, 95%CI 1.35-2.39, p<0.001) or were administered any forms of ISMN other than at bedtime (HR 1.90, 95%CI 1.41-2.57, p<0.001) had a significantly higher risk of MACE compared with the non-nitrate group. Nicorandil was shown to have a neutral effect on VSA patients (HR 1.11, 95%CI 0.73-1.69, p=0.62).

CONCLUSIONS

The long-term use of nitrate therapy was associated with increased risk of adverse cardiac events in VSA patients. The use of immediate-release ISMN or the administration of ISMN other than at bedtime was related with poor outcomes of VSA patients.

Off-Pump Coronary Artery Bypass Graft Versus Drug-Eluting Stent Implantation in Patients with Multivessel Disease Involving the Right Coronary Artery

BACKGROUND

 Whether percutaneous coronary intervention (PCI) is superior to coronary artery bypass grafting (CABG) for the right coronary territory is unknown. The aim of this study was to compare the outcomes and patency in the right coronary territory after CABG or PCI.

METHODS

 We studied 2,467 multivessel coronary artery disease patients from January 2001 to December 2011; 1,672 were off-pump CABG patients and 795 were PCI. The graft patency and the presence of major adverse cardiac and cerebrovascular events (MACCEs) including death, myocardial infarction, target vessel revascularization, and stroke were analyzed.

RESULTS

 After propensity score matching, cardiac-related survival was found to be significantly higher in the CABG group than in the PCI group (hazard ratio (HR) for the PCI group: 2.445, p = 0.006). The PCI group showed higher rates of myocardial infarction (HR: 2.571, p = 0.011) and target vessel revascularization (HR: 3.337, p < 0.001). In the right coronary territory, the right internal thoracic artery patency was not different in the PCI group compared with the CABG group (p = 0.248). In CABG group, low right coronary artery graft patency was associated with cardiac-related death (HR: 0.17, p = 0.003) and the occurrence of MACCEs (HR: 0.22, p < 0.001).

CONCLUSION

 CABG was superior to PCI in patients with multivessel disease. Low graft patency in the right coronary territory was associated with cardiac-related death and the occurrence of MACCEs.

Detecting and correcting for publication bias in meta-analysis – A truncated normal distribution approach

Publication bias can significantly limit the validity of meta-analysis when trying to draw conclusion about a research question from independent studies. Most research on detection and correction for publication bias in meta-analysis focus mainly on funnel plot-based methodologies or selection models. In this paper, we formulate publication bias as a truncated distribution problem, and propose new parametric solutions. We develop methodologies of estimating the underlying overall effect size and the severity of publication bias. We distinguish the two major situations, in which publication bias may be induced by: (1) small effect size or (2) large p-value. We consider both fixed and random effects models, and derive estimators for the overall mean and the truncation proportion. These estimators will be obtained using maximum likelihood estimation and method of moments under fixed- and random-effects models, respectively. We carried out extensive simulation studies to evaluate the performance of our methodology, and to compare with the non-parametric Trim and Fill method based on funnel plot. We find that our methods based on truncated normal distribution perform consistently well, both in detecting and correcting publication bias under various situations.

Clopidogrel Versus Aspirin as an Antiplatelet Monotherapy After 12-Month Dual-Antiplatelet Therapy in the Era of Drug-Eluting Stents

BACKGROUND

The use of dual-antiplatelet therapy (DAPT) exceeding 12 months may increase a bleeding risk despite a lower risk of ischemic events. There is no study to compare clinical outcomes in patients treated with a single-antiplatelet drug after DAPT in the era of drug-eluting stents (DES). We sought to investigate the efficacy and safety of clopidogrel versus aspirin monotherapy after 12-month DAPT after DES implantation using an institutional registry.

METHODS AND RESULTS

This observational study was conducted on consecutive patients receiving DES between January 2003 and December 2010. A total of 3243 patients receiving 12-month DAPT after DES implantation without adverse clinical outcomes were divided into 2 groups based on prescribed antiplatelet status: aspirin (n=2472) and clopidogrel (n=771). Clinical, angiographic, and procedural characteristics revealed more comorbidities and more complex lesions in the clopidogrel group than in the aspirin group. At 36 months after initiation of antiplatelet monotherapy, clopidogrel was associated with a reduction in risk for a composite of cardiac death, myocardial infarction, or stroke (aspirin versus clopidogrel; 3.8% versus 2.6%; hazard ratio, 0.54; 95% confidence interval, 0.32-0.92; P=0.02). The risk of cardiac death was lower with clopidogrel monotherapy than with aspirin monotherapy (1.4% versus 0.5%; hazard ratio, 0.31; 95% confidence interval, 0.11-0.93; P=0.04). Thrombolysis in myocardial infarction major bleeding occurred similarly between both groups (0.9% versus 1.3%; hazard ratio, 1.03; 95% confidence interval, 0.46-2.32; P=0.95).

CONCLUSIONS

After 12-month DAPT, clopidogrel monotherapy, when compared with aspirin monotherapy, might be associated with a reduced risk of recurrent ischemic events in patients receiving DES.

Comorbidity as a contributor to frequent severe acute exacerbation in COPD patients

Background

Comorbidities have a serious impact on the frequent severe acute exacerbations (AEs) in patients with COPD. Previous studies have used the Charlson comorbidity index to represent a conglomerate of comorbidities; however, the respective contribution of each coexisting disease to the frequent severe AEs remains unclear.

Methods

A retrospective, observational study was performed in 77 COPD patients who experienced severe AE between January 2012 and December 2014 and had at least 1-year follow-up period from the date of admission for severe AE. We explored the incidence of frequent severe AEs (≥2 severe AEs during 1-year period) in these patients and investigated COPD-related factors and comorbidities as potential risk factors of these exacerbations.

Results

Out of 77 patients, 61 patients (79.2%) had at least one comorbidity. During a 1-year follow-up period, 29 patients (37.7%) experienced frequent severe AEs, approximately two-thirds (n=19) of which occurred within the first 90 days after admission. Compared with patients not experiencing frequent severe AEs, these patients were more likely to have poor lung function and receive home oxygen therapy and long-term oral steroids. In multiple logistic regression analysis, coexisting asthma (adjusted odds ratio [OR] =4.02, 95% confidence interval [CI] =1.30–12.46, P=0.016), home oxygen therapy (adjusted OR =9.39, 95% CI =1.60–55.30, P=0.013), and C-reactive protein (adjusted OR =1.09, 95% CI =1.01–1.19, P=0.036) were associated with frequent severe AEs. In addition, poor lung function, as measured by forced expiratory volume in 1 second (adjusted OR =0.16, 95% CI =0.04–0.70, P=0.015), was inversely associated with early (ie, within 90 days of admission) frequent severe AEs.

Conclusion

Based on our study, among COPD-related comorbidities, coexisting asthma has a significant impact on the frequent severe AEs in COPD patients.

Clinical implications of low-dose aspirin on vasospastic angina patients without significant coronary artery stenosis; a propensity score-matched analysis

BACKGROUND

High-dose aspirin has been reported to exacerbate coronary artery spasm in patients with vasospastic angina. We investigated clinical implications of low-dose aspirin on vasospastic angina patients without significant coronary artery stenosis.

METHODS

We included patients without significant coronary artery stenosis on coronary angiography (CAG) and with positive results on intracoronary ergonovine provocation test between January 2003 and December 2014. A total of 777 patients were divided into two groups according to prescription of low-dose aspirin at discharge: aspirin group (n=321) and non-aspirin group (n=456). The major adverse cardiovascular events (MACE), defined as composite outcomes of cardiac death, acute myocardial infarction, revascularization, or rehospitalization requiring CAG or medication change due to recurrent angina were compared.

RESULTS

The aspirin group had significantly higher incidence of MACE (22.8% versus 12.1%; p=0.04) and had higher tendency for rehospitalization (20.6% versus 11.2%; p=0.08). All-cause mortality and cardiac death were similar between the two groups. After propensity score matching, the aspirin group had greater risk of MACE (hazard ratio [HR] 1.54; 95% confidence interval [CI], 1.04-2.28; p=0.037) and rehospitalization requiring CAG (HR, 1.33; 95% CI, 1.13-4.20; p=0.03), and a higher tendency for rehospitalization (HR, 1.40; 95% CI, 0.94-2.09; p=0.12).

CONCLUSION

In vasospastic angina without significant coronary artery stenosis, patients taking low-dose aspirin are at higher risk of MACE, driven primarily by tendency toward rehospitalization. Low-dose aspirin might be used with caution in vasospastic angina patients without significant coronary artery stenosis.

Aortic Valve Replacement With Carpentier-Edwards: Hemodynamic Outcomes for the 19-mm Valve

BACKGROUND

To compare hemodynamic performance and clinical outcomes after aortic valve replacement for aortic stenosis with the 19-mm Carpentier-Edwards pericardial bioprosthesis versus larger valves.

METHODS

Between January 1998 and December 2013, 447 consecutive patients underwent aortic valve replacement for aortic stenosis with the Carpentier-Edwards Perimount (n = 61) or Magna bioprostheses (n = 386). Based on the implanted valve size, the patients were classified into three groups: a 19-mm group (n = 54), a 21-mm group (n = 154), and a 23-mm to 27-mm group (n = 239). The in vivo effective orifice area index was measured by transthoracic echocardiography 12 months after operation (n = 331). The mean follow-up time was 4.9 ± 3.5 (maximum 15.4) years.

RESULTS

There were three early deaths (0.7%). At 10 years, overall survival (84.1%) was unaffected by patient-prosthesis mismatch (18.7%, 62 patients), and freedom from structural valve deterioration and endocarditis was 100% and 97.1%, respectively. Although the 19-mm group was significantly older and had a higher incidence of patient-prosthesis mismatch (n = 14, 30.4%), there were no significant differences in early outcomes, overall survival, cardiac-related mortality, or serial reduction of left ventricular mass index in comparison with patients with a larger bioprostheses. Independent risk factors for all-cause mortality were age, male gender, combined coronary artery bypass graft, and low hemoglobin level.

CONCLUSION

The Carpentier-Edwards pericardial bioprosthesis appears to be associated with acceptable clinical outcomes and hemodynamic profile.

Pure Bilateral Internal Thoracic Artery Grafting in Diabetic Patients With Triple-Vessel Disease

BACKGROUND

Despite the documented superior long-term patency of bilateral internal thoracic artery (BITA) grafting, use of BITAs remains low, especially in diabetic patients. We analyzed the results of pure BITA grafting to determine whether the potential survival advantage outweighs the risk of wound infection in diabetic patients.

METHODS

We performed a retrospective analysis of 791 consecutive patients (389 diabetic, 402 nondiabetic) with triple-vessel disease who underwent off-pump coronary artery bypass using only skeletonized BITAs from 2001 to 2010. We used propensity score matching to match 315 nondiabetic patients with diabetic patients.

RESULTS

The groups did not differ significantly regarding 10-year survival (diabetic, 84.2% ± 4.5%; nondiabetic, 80.8% ± 4.7%; p = 0.828) or freedom from major adverse cardiovascular events (diabetic, 73.5% ± 5.2%; nondiabetic, 71.8% ± 5.3%; p = 0.431). Diabetes was not predictive of deep sternal infection (odds ratio, 1.11; 95% confidence interval, 0.23 to 5.31; p = 0.895). Results of stratified competing risks regression analysis showed that the risk of target vessel revascularization in diabetic patients was similar to that of nondiabetic patients (subdistribution hazard ratio, 0.67; 95% confidence interval, 0.16 to 2.80; p = 0.585).

CONCLUSIONS

Off-pump coronary artery bypass grafting using pure BITAs produced excellent clinical outcomes in both diabetic and nondiabetic patients. This strategy did not increase the incidence of deep sternal infection in diabetic patients. We recommend BITA grafting, which has proven long-term patency, as a strategy of choice in diabetic patients.

Explaining Alberta's rising mesothelioma rates

Although mesothelioma rates have been rising worldwide, little is known about mesothelioma trends in Alberta. This population-based descriptive study used Alberta Cancer Board Registry data from 1980 to 2004 to develop an age-period-cohort model of male pleural mesothelioma incidence rates over time. Both age and cohort effects are associated with incidence rates. The highest-risk cohort comprised men born between 1930 and 1939, reflecting widespread asbestos use and exposure beginning in the 1940s in Canada. We predict that 1393 Albertan men 40 years and older will die of pleural mesothelioma between 1980 and 2024; 783 (56.2%) of these deaths will occur between 2010 and 2024. The total number of mesothelioma deaths in Alberta will be higher when all age groups, both sexes, and all disease sites are included, with numbers likely peaking sometime between 2015 and 2019. In addition to the ongoing efforts that focus on eliminating asbestos-related disease in Alberta, the challenge is to implement surveillance systems to prevent future epidemics of preventable occupational cancers in Alberta.

A general method for identifying excess revisit rates: the case of hypertension

OBJECTIVE

To provide a description and application of a novel methodology for comparing actual to expected visit rates at the physician level (controlling for patient characteristics) that could be employed in healthcare monitoring and management.

DATA SOURCES/STUDY SETTING

Two fiscal years (1997/1998 and 1998/1999) of health utilization data extracted from linked administrative data sets on a population-based cohort of 13,688 patients (aged 25+ with hypertension) involving 157 physicians.

STUDY DESIGN

We re-analyzed data from a previously published retrospective cohort study to develop and apply a new methodology for identifying higher or lower than expected physician visit rates for hypertension.

DATA COLLECTION/EXTRACTION METHODS

We matched each study physician's hypertensive patients on the basis of age, sex, income and co-morbidity to an equal number of control patients drawn from the cohort. We then compared visit rates between the actual practice and the matched control practice.

PRINCIPAL FINDINGS

Although the correlation between the visit rates of the two groups of practices was high (r=.87), there were notable differences in rates, suggesting substantial discretionary practice among physicians.

CONCLUSIONS

The methodology outlined in this paper provides a basis for identifying variations in visit levels related to discretionary practice patterns and patient preferences. Deviation from expected visit rates provides a potentially useful measure for performance feedback and quality improvement activities.

Increased continuity of care associated with decreased hospital care and emergency department visits for patients with asthma

The objective of this study was to determine the association between continuity of care and emergency room visits/hospital care for patients with asthma. A population-based study was conducted using administrative healthcare datasets obtained from Alberta Health and Wellness, Alberta, Canada. The 4-year study period extended from April 1, 1996 to March 31, 2000, and took place at the Palliser Health Region in Alberta, Canada, which has a population of 88,000 people. A population-based sample of 2774 patients, diagnosed with asthma between ages 5 and 45 with two or more office visits for asthma and who lived in the Palliser Health Region for 2 consecutive years during the study period, was studied. The main outcome measure was the association of continuity of care with hospitalizations and emergency room visits for patients with asthma. Continuity of care was the proportion of total physician visits made to the most frequently visited physician. High continuity of care was associated with a decreased risk of an emergency visit (OR = 0.24: 95% CI 0.19-0.29), number of emergency visits (RR = 0.37; 95% CI 0.32-0.42), decreased risk of number of hospitalizations (RR = 0.69; 95% CI 0.54-0.89), and total days in hospital (average difference = 0.77; 95% CI 0.63-0.95), but not with ever hospitalized. High continuity of care was associated with a 60%-75% reduction in emergency room visits and an approximate 25% reduction in number of hospitalizations in patients with asthma. Interventions to improve continuity of care could have the potential to improve care and reduce cost.

On group sequential procedures under variance heterogeneity

In this paper, we consider group sequential procedures for clinical trials under variance heterogeneity. Group sequential procedures typically involve small samples at each interim analysis. We advocate Welch's correction for variance heterogeneity, and present a natural application of the significance level method for such situations. Currently available procedures are based on a large sample method, with no allowance for corrections of heterogeneity. Unless the sample size is large, the results are not valid. On the basis of simulation studies, comparing their abilities to control Type I error rates, we recommend using Welch's correction for sequential trials involving small samples under variance heterogeneity.

Appropriate antibiotic utilization in seniors prior to hospitalization for community-acquired pneumonia is associated with decreased in-hospital mortality

BACKGROUND

We analysed the association of mortality and prescription of antibiotics prior to hospitalization for community-acquired pneumonia.

METHODS

We used administrative data (hospital abstracts, physician claims, prescriptions) for seniors (age 61 years and over) for Alberta, Canada from 1 April 1994 to 31 March 1999.

RESULTS

Hospitalization of 21 191 seniors occurred during the study period. In about 43% of hospitalizations (n = 9034), a physician was consulted prior to hospital admission. Antibiotics were dispensed to 31% of those with a prior physician visit and in about 72%, the antibiotic choice was deemed appropriate. The odds for mortality were significantly decreased in those with prior physician visits (OR = 0.87, P < 0.01), with any antibiotic prescription (OR = 0.66, P < 0.0001), and with an appropriate antibiotic (OR = 0.68, P = 0.03). The choice of an appropriate antibiotic as opposed to an inappropriate antibiotic resulted in a 2.6% absolute and 38% relative mortality reduction.

CONCLUSION

Choosing an appropriate outpatient antibiotic in accordance with published expert opinion guidelines compared with inappropriate antibiotic prescriptions decreased hospital mortality in patients subsequently hospitalized for community-acquired pneumonia.

Agreement between patient and proxy assessments of health-related quality of life after stroke using the EQ-5D and Health Utilities Index

BACKGROUND AND PURPOSE

Proxy informants can provide information on patients who are limited in ability to self-assess health-related quality of life (HRQL) after stroke. One alternative is to exclude assessments of such patients and attenuate generalizability. The purpose of this study was to examine patient-proxy agreement on the domains and summary scores of the EQ-5D and Health Utilities Index Mark 3 (HUI3) after stroke.

METHODS

An observational longitudinal cohort of 124 patients hospitalized after ischemic stroke and their family caregivers completed the HRQL measures at baseline and were followed up for 6 months. Patient and proxy agreement was assessed by use of weighted kappa or the intraclass correlation coefficient (ICC).

RESULTS

At baseline, the more observable domains of HRQL demonstrated greater agreement than the more subjective components. Cross-sectional point estimates of agreement were generally acceptable (ICC >0.70) for the EQ-5D Index and HUI3 summary scores when assessed >or=1 month after baseline. Agreement between change scores was generally poor to fair (ICC <0.60), but systematic bias was not observed for the indirect preference-based summary scores between baseline and 6 months.

CONCLUSIONS

Results suggest that proxy assessments obtained 6 months after stroke are more reliable than those obtained within 2 to 3 weeks after stroke. Although proxy-assessed change scores for indirect preference-based summary scores of the EQ-5D and HUI3 provided suboptimal agreement with patient assessment, limited systematic bias may support their consideration as alternatives to missing data or statistical imputation. Further research into the validity and reliability of proxy assessments is suggested.

Mortality during hospitalisation for pneumonia in Alberta, Canada, is associated with physician volume

The association of mortality with patient factors (severity of illness, comorbidity), physician factors (specialty training, prehospitalisation visit, in-hospital consultation, volume of patients seen per physician) and healthcare organisation factors (patient-travel distances, regional beds per capita, admitting hospital-bed occupancy, admitting hospital-bed turnover, hospital location, volume of pneumonia cases per hospital) after hospital admission with community-acquired pneumonia was investigated using administrative data from Alberta, Canada from April 1, 1994-March 31, 1999. During the 5-yr study period there were 43,642 pneumonia hospitalisations, with an 11% in-hospital and 26% 1-yr mortality. Patient severity of illness and comorbidity were the strongest predictors of increased mortality. Physicians with the highest in-hospital pneumonia patient volume (>27 patients x yr(-1)) cared for patients with greater severity/comorbidity, but with decreased odds of in-hospital mortality, compared with the lowest volume physicians (less than seven patients per year). The effects of internal medicine specialist or subspecialist care were mixed, with a reduction in deaths for the first 72 h and an increase in in-hospital deaths. Prehospitalisation visit by a physician was associated with decreased mortality. Healthcare organisation factors were the least strong predictor of mortality, demonstrating an effect only for 1-yr mortality in those discharged alive from hospital. Admissions to larger volume or metropolitan hospitals were associated with a decrease in mortality. Severity of illness and comorbidity had the strongest association with mortality. The first association of high-volume physician and pre-hospital care with decreased in-hospital mortality for community-acquired pneumonia is reported.

Embedding child health within a framework of regional health: population health status and sociodemographic indicators

OBJECTIVE

The description of regional variation in children's health requires regional population-based context. But what is the best way to measure the health of a region's population?

METHODS

The use of two indicators is described--one a health status measure and the other a measure of socioeconomic wellbeing. It is well known that the population's premature mortality rate (PMR), the age/sex-adjusted rate of death before age 75 years, is highly related to overall health status of an area's residents. Socioeconomic characteristics of an area's residents are also indicative (and likely causative) of health status differences.

RESULTS

The Socioeconomic Factor Index (SEFI) was developed at the Manitoba Centre for Health Policy, using a Principal Components Analysis of census data. PMR and SEFI are highly correlated (Spearman's correlation coefficient r = 0.85, p < 0.0001).

CONCLUSION

PMR can be used as a surrogate measure for both the health status and socioeconomic well-being of regional populations in Manitoba.

Variation in management of community-acquired pneumonia requiring admission to Alberta, Canada hospitals

Previous studies have shown small area variation in the rate of admission to hospital for patients with community-acquired pneumonia. We determined the rates of admission and length of stay for patients with community-acquired pneumonia in Alberta and the factors influencing admission rates and length of stay. Using hospital abstracts, hospital admissions for community-acquired pneumonia from 1 April 1994 to 31 March 1999 were compared. We classified Alberta hospitals according to geographical regions, by the number of beds, and by number of community-acquired pneumonia cases. There were 12,000 annual hospital discharges for community-acquired pneumonia costing over $40 million per year. The overall in-hospital mortality rate was 12% and the 1 year mortality rate was 26%. Compared with rural hospitals, regional and metropolitan hospitals admitted patients with greater severity of illness as demonstrated by greater in-hospital mortality, cost per case and comorbidity. Age-sex adjusted hospital discharge rates were significantly below the provincial average in both urban regions. Hospital discharge rates for residents in all rural regions and 4 of 5 regions with a regional hospital were significantly higher than the provincial average. After adjusting for comorbidity, the relative risk for a longer length of stay was 22% greater in regional hospitals and about 30% greater in urban hospitals compared to rural hospitals. Seasonal variation in the admission rate was evident, with higher rates in the winter of each year. We conclude that rural hospitals would be likely to benefit from a protocol to help with the admission decision and urban hospitals from a programme to reduce length of stay.

Embedding child health within a framework of regional health: population health status and sociodemographic indicators

OBJECTIVE

The description of regional variation in children's health requires regional population-based context. But what is the best way to measure the health of a region's population?

METHODS

The use of two indicators is described--one a health status measure and the other a measure of socioeconomic wellbeing. It is well known that the population's premature mortality rate (PMR), the age/sex-adjusted rate of death before age 75 years, is highly related to overall health status of an area's residents. Socioeconomic characteristics of an area's residents are also indicative (and likely causative) of health status differences.

RESULTS

The Socioeconomic Factor Index (SEFI) was developed at the Manitoba Centre for Health Policy, using a Principal Components Analysis of census data. PMR and SEFI are highly correlated (Spearman's correlation coefficient r = 0.85, p < 0.0001).

CONCLUSION

PMR can be used as a surrogate measure for both the health status and socioeconomic well-being of regional populations in Manitoba.

Continuity of care and health decline associated with a hip fracture

OBJECTIVES

Identify determinants of health decline associated with hip fracture with the goal of designing interventions.

METHOD

Prefracture and postfracture information was obtained from participants aged 65-plus years fracturing a hip between July 1996 and August 1997. Health utilization data were linked to the cohort data and to an age-gender matched cohort of nonfracture seniors.

RESULTS

Fracture patients were likely to have been hospitalized and have low continuity of care. Patients making frequent physician visits were at increased risk of both prefracture hospitalization and postfracture health decline. Prefracture hospitalization was less likely for patients with high physical function; patients of high mental status were less likely to experience postfracture health decline.

DISCUSSION

Health appears to be in decline prefracture. Patients may benefit from continuous physician care to prevent further health deterioration. Some hip fractures can be prevented by identifying high-risk seniors at an early stage and intervening to prevent falls.

Assessing socioeconomic effects on different sized populations: to weight or not to weight?

OBJECTIVE

Researchers in health care often use ecological data from population aggregates of different sizes. This paper deals with a fundamental methodological issue relating to the use of such data. This study investigates the question of whether, in doing analyses involving different areas, the estimating equations should be weighted by the populations of those areas. It is argued that the correct answer to that question turns on some deep epistemological issues that have been little considered in the public health literature.

DESIGN

To illustrate the issue, an example is presented that estimates entitlements to primary physician visits in Manitoba, Canada based on age/gender and socioeconomic status using both population weighted and unweighted regression analyses.

SETTING AND SUBJECTS

The entire population of the province furnish the data. Primary care visits to physicians based on administrative data, demographics and a measure of socioeconomic status (SERI), based on census data, constitute the measures.

RESULTS

Significant differences between weighted and unweighted analyses are shown to emerge, with the weighted analyses biasing entitlements towards the more populous and advantaged population.

CONCLUSIONS

The authors endorse the position that, in certain problems, data analyses involving population aggregates unweighted by population size are more appropriate and normatively justifiable than are analyses weighted by population. In particular, when the aggregated units make sense, theoretically, as units, it is more appropriate to carry out the analyses without weighting by the size of the units. Unweighted analyses yield more valid estimations.

Functional dependence after hip fracture

OBJECTIVES

To identify patients at high risk of functional dependence and examine the progression of disability after a hip fracture.

DESIGN

This was a population-based prospective inception cohort study of all patients aged 65+ yr who fractured a hip between July 1996 and August 1997. Demographic, socioeconomic, social support, and health status information was assessed in the hospital and 3 mo postfracture.

RESULTS

The analysis included 367 patients. Almost all patients with cognitive impairment were functionally dependent postfracture, with new disabilities frequently occurring in transferring. Among patients of high mental status, increased risk of functional dependence was associated with advanced age, more co-morbidities, hip pain, poor self-rated health, and previous employment in a prestigeous occupation. Bathing disability was most likely in those who functioned independently prefracture; a disability in dressing was most common otherwise.

CONCLUSION

Hip pain is amenable to treatment and may improve chances of functional recovery. Patients can be assisted in regaining prefracture function if they are targeted for rehabilitation on the basis of mental status. The focus should be on bathing and dressing among patients of high cognition and transferring among those patients with mental impairment.

Hypertensive patients and their general practitioners

This study examined the relative contribution of hypertensive patients and their physicians in selecting total annual physician visit frequencies and made regional comparisons between two Canadian cities. We found that the frequency of physician visits was primarily influenced by physician referrals and physician practice patterns, which accounted for about 80 percent of the total explainable variance in physician visits. The relative contribution of other available patient and physician characteristics in determining visit frequency was rather small.

Testing for the presence of cured patients: a simulation study

An important but difficult problem in clinical trials is to determine the presence of cured patients when long-term survivors are observed. The likelihood ratio test has been studied for this purpose in the gamma mixture model. However, its asymptotic null distribution is not readily available due to a violation of boundary conditions in the standard asymptotic theory. In this paper, a simulation study is employed to examine a proposed asymptotic null distribution of the likelihood ratio test. We find that the distribution can also be used to approximate the asymptotic null distribution of the likelihood ratio test in the Weibull and log-normal mixture models when the censoring rate is not too light. However, the simulation study also shows that null distribution of the likelihood ratio test deviates significantly from the suggested distribution under moderate sample sizes when the censoring rate is small or the hazard rate is large. Consequently caution is needed in this case to determine the presence of cured patients. Finally, the results are used to confirm the presence of cured patients in a leukaemia study.

Health care seeking behavior following a health survey: impact on prevalence estimates of chronic diseases

This article addresses the time sequence between a population health survey and subsequent health care use and how this changes the incidence estimates of selected chronic diseases. A cardiovascular survey of a representative sample of the adult population of Manitoba, Canada was linked with the health insurance claims database. Of the 2792 subjects in the survey, 98% were linked successfully, using an encrypted personal health insurance number. Five years of physician claims data for the survey participants were reviewed including 18 months prior to and 42 months following the survey. Survey participants started seeking confirmation of possible hypertension as soon as they received blood pressure information at the interview. Confirmation of diabetes and elevated cholesterol were not completed until 3-4 months after participants had received the laboratory test results. As many as 4.6 times more new cases of hypertension per month, 5.1 times more cases of elevated cholesterol, and 3.3 times more cases of diabetes were diagnosed following the survey. Surveys designed to determine the prevalence of specific chronic diseases generate new cases within a short time afterwards, thus affecting the original prevalence estimates. The process of assessing the burden of disease in a population is dynamic rather than static, and comparisons across populations need to take into account the frequency and recency of past surveys.

Across time and space: variations in hospital use during Canadian health reform

OBJECTIVES

To investigate change in hospital utilization in a population and to discuss analytical strategies using large administrative databases, focusing on variations in rates of different types of hospital utilization by income quintile neighborhoods.

DATA SOURCES

Hospital discharge abstracts from Manitoba Health, used to study the changes in utilization rates over eight fiscal years (1989-1996).

STUDY DESIGN

We test the hypotheses that health reform has changed utilization rates, that utilization rates differ significantly across income quintiles (defined by the relative affluence of neighborhood of residence), and that these variations have been maintained over time. Our approach uses generalized estimating equations to produce robust and consistent results for studying rates of recurrent and nonrecurrent events longitudinally.

DATA EXTRACTION METHODS

Rates of individuals hospitalized, hospital discharges, days of hospitalization, and hospitalization for different types of medical conditions and surgical procedures are generated for the period April 1, 1989 through March 31, 1997 for residents of Winnipeg, Manitoba. Data are grouped according to the individual's age, gender, and neighborhood of residence on April 1 of each of the eight fiscal years for the rate calculations. Neighborhood of residence and the 1991 Canadian Census public use database are used to assign individuals to income quintiles.

PRINCIPAL FINDINGS

The substitution of outpatient surgery for inhospital surgery accounted for much of the change in hospital utilization over the 1989-1996 period. Health care reform did not have a significant effect on the utilization gradient already observed across socioeconomic groups. Health reform markedly accelerated declines in in-hospital utilization.

CONCLUSIONS

Grouping the data with key characteristics intact facilitates the statistical analysis of utilization measures previously difficult to study. Such analyses of variations across time and space based on parametric models allows adjustment for continuous covariates and is more efficient than the traditional nonparametric approach using standardized rates.

Comparing sub-survival functions in a competing risks model

In the competing risks literature, one usually compares whether two risks are equal or whether one is "more serious." In this paper, we propose tests for the equality of two competing risks against an ordered alternative specified by their sub-survival functions. These tests are naturally developed as extensions of those based on hazard rates and cumulative incidence functions. We note that the interpretation of the new test results is more direct compared to the situation when the hypotheses are framed in terms of their cumulative incidence functions. The proposed tests are of the Kolmogrov-Smirnov type, based on maximum differences between sub-survival functions. Our simulation studies indicate that they are excellent competitors of the existing tests, that are based mainly on differences between cumulative incidence functions. A numerical example will demonstrate the advantages of the proposed tests.

Hepatitis C prevalence and risk factors in the northern Alberta dialysis population

Hepatitis C virus (HCV) is an emerging global public health issue with particular relevance in multiply transfused renal dialysis patients. This cross-sectional study evaluated the prevalence and risk factors for HCV infection among renal dialysis patients in northern Alberta, Canada. Ninety-two percent of eligible patients (n = 336) provided informed consent to participate. Participants were interviewed to gather risk factor information and, using multiple logistic regression analysis with exact inference, a predictive model for HCV infection in this population was developed. The prevalence of HCV infection in the population was 6.5%, and all positive patients had at least one identifiable risk factor. The multivariate analysis showed that the risk of HCV infection was greater for those in the 18-55 years age category (odds ratio (OR) = 4.9, 95% confidence interval (CI) 1.2-27.9), patients who had been on dialysis > 5 years (OR = 3.7, 95% CI 1.2-12.0), and patients who had > or = 2 high risk life-style behaviors (OR = 5.0, 95% CI 1.5-16.7). Transfusion prior to 1990 was marginally associated with HCV status (OR = 4.0, 95% CI 0.96-16.3). This study documented previously unreported life-style risk factors for HCV infection in patients with renal failure, confirmed the expected decline in transfusion-acquired HCV infection in this population, and provided evidence against nosocomial transmission of HCV.

Waiting times for surgical procedures

OBJECTIVES

Polls show that nearly two thirds of Canadians believe that waiting times prior to surgery have increased in recent years. A study was undertaken in Manitoba to determine whether public perceptions about long and increasing waits were valid.

RESEARCH DESIGN

Using administrative data, waiting times for 10 types of surgery-ranging from coronary artery bypass surgery and mastectomy to cataract surgery and hernia repairs-were studied over a 5-year period.

RESULTS

Using each patient's preoperative visit to the surgeon as the beginning of the waiting time, median waiting times for most of the procedures studied were found to have, in fact, remained stable or fallen slightly over the period studied.

CONCLUSIONS

Further, an examination of waiting times for cataract surgery demonstrated that allowing surgeons to practice in both public and private arenas seems to be counterproductive to providing good public service.

Assessing the extent to which hospitals are used for acute care purposes

OBJECTIVES

The degree to which Manitobans were appropriately hospitalized for medical conditions was assessed using a retrospective chart review of a sample of patients in 26 hospitals.

RESEARCH DESIGN

A standardized set of object-based, nondiagnostic criteria (Inter-Qual) was used by trained abstractors to assess the patient at admission and for each day of stay.

RESULTS

A high percentage of admissions and days of care were inappropriate. Overall, 49.5% of medical patients were acute at the time of admission, 1.6% required no health care services, and 48.9% could have received care through alternate methods or facilities. Only 33.4% of the subsequent days of stay were appropriate. For patients assessed as acute at the time of admission, by the 8th day of stay, only 47% were still acute and by day 30, only 27% were acute. Patients aged 75 years or older were just as likely to be acute at the time of admission as were younger patients; however, they accounted for 54% of the days in the study, and fewer than 30% of these days were acute. Our data suggest that despite their high use of hospitals, disadvantaged groups (the poor, aboriginal Manitobans), have the same levels of appropriateness as others.

CONCLUSIONS

We conclude that alternatives to hospital care must first be established and made known and available before a shift in health care resources can occur.

Managing health services: how the Population Health Information System (POPULIS) works for policymakers

OBJECTIVES

University-based researchers in Manitoba, Canada, have used administrative data routinely collected as part of the national health insurance plan to design an integrated database and population-based health information system. This information system is proving useful to policymakers for answering such questions as: Which populations need more physician services? Which need fewer? Are high-risk populations poorly served? or do they have poor health outcomes despite being well served? Does high utilization represent overuse? or is it related to high need? More specifically, this system provides decision makers with the capability to make critical comparisons across regions and subregions of residents' health status, socioeconomic risk characteristics and use of hospitals, nursing homes, and physicians. The system permits analyses of demographic changes, expenditure patterns, and hospital performance in relation to the population served. The integrated database has also facilitated outcomes research across hospitals and countries, utilization review within a single hospital, and longitudinal research on health reform. The discussion highlights the strengths of integrated population-based information in analyzing the health care system and raising important questions about the relationship between health care and health.

Needs-based planning for generalist physicians

OBJECTIVES

The Manitoba Centre for Health Policy and Evaluation (MCHPE) collaborated with a provincially-appointed Physician Resource Committee in an assessment of provincial physician resources.

RESEARCH DESIGN

Beginning with map-based analyses of physician supply and contacts across the province, compared with the health and socioeconomic characteristics of local populations, the study moved to a needs-based, regression-based approach to physician resource planning.

RESULTS

The results challenged the popular belief that Manitoba suffers from an increasing shortage of physicians. A handful of high-need, low-supply and low-use areas are identified, as is the expensive surplus of generalist physicians in Winnipeg. (Generalist physicians include general and family practitioners as well as general internists and pediatricians.) No relationship between physician supply and health characteristics of populations, or between high physician supply and low hospital use patterns were found. Given the Committee's interest in what drives high physician contact rates, analyses of visit patterns of hypertensive patients were undertaken. We found that patients who had more complex medical conditions made more contacts, but that after controlling for this and other key patient characteristics, the patient's primary care physician's patient recall rate was a strong influence on how frequently visits were made.

Regulatory affairs in biotechnology: optimal statistical designs for biomedical experiments

One of the major issues in all applications of biotechnology is how to regulate the process through which new technological information is produced. The end products of biotechnological applications are diverse (e.g., better drugs, better interventions, better fertilizers). Such applications should be properly regulated to obtain valid scientific findings in the most efficient way possible. Some statistically optimal designs are more popularly employed than others as regulatory tools in medical, pharmaceutical and clinical trials. The statistical and practical properties (strengths and weaknesses) are presented to better appreciate their optimality. Recent developments on some related issues are also reviewed.

Managing health services: how administrative data and population-based analyses can focus the agenda

University-based researchers in Manitoba, Canada, have used administrative data routinely collected as part of the national health insurance plan to design an integrated database and population-based health information system. This information system is proving useful to policymakers for providing answers to such questions as: which populations need more physician services? Which need fewer? Are high-risk populations poorly served or do they have poor health outcomes despite being well served? Does high utilization represent overuse or utilization related to high need? More specifically, this system provides decision-makers with the capability to make critical comparisons across regions and subregions of residents' health status, socioeconomic risk characteristics, and use of hospitals, nursing homes, and physicians. The system permits analyses of demographic changes, expenditure patterns, and hospital performance in relation to the population served. The integrated database has also facilitated outcomes research across hospitals and counties, utilization review within a single hospital, and longitudinal research on health reform. A particularly interesting application to planning physician supply and distribution is discussed. The discussion highlights the strengths of integrated population-based information in analyzing the health care system and raising important questions about the relationship between health care and health.

Information needs and decisional preferences in women with breast cancer

OBJECTIVE

To determine the degree of involvement women with breast cancer wanted in medical decision making, extent to which they believed they had achieved their preferred level of involvement, and types of information they judged to be most important.

DESIGN AND SETTING

Cross-sectional survey at 2 tertiary oncology referral clinics and 2 community hospital oncology clinics in Winnipeg, Manitoba.

PATIENTS

Consecutive sample of 1012 women with a confirmed diagnosis of breast cancer who were scheduled for a visit at 1 of 4 hospital oncology clinics.

MAIN OUTCOME MEASURES

The following measures were used: (1) Preferences about various levels of participation in treatment decision making; (2) the extent to which subjects believed they had achieved their preferred levels of involvement in decision making; and (3) priority needs for information and how these needs differed by selected sociodemographic, disease, and treatment variables.

RESULTS

A total of 22% of women wanted to select their own cancer treatment, 44% wanted to select their treatment collaboratively with their physicians, and 34% wanted to delegate this responsibility to their physicians. Only 42% of women believed they had achieved their preferred level of control in decision making. The 2 most highly ranked types of information were related to knowing about chances of cure and spread of disease. Women younger than 50 years rated information about physical and sexual attractiveness as more important than did older women (P<.001); women older than 70 years rated information about self-care as more important than did younger women (P=.002); and women who had a positive family history of breast cancer rated information about family risk as more important than did other women (P=.03).

CONCLUSIONS

The substantial discrepancy between women's preferred and attained levels of involvement in treatment decision making suggests that systematic approaches to assess and respond to women's desired level of participation in treatment decision making need to be evaluated. Priorities for information identified in this study provide an empirical basis to guide communication with women seeking care for breast cancer.

Income level and asthma prevalence and care patterns

Manitoba has a universally accessible health-care system that records physician contacts and hospitalizations in such a way that they can be ascribed to individuals. We examined the prevalence of physician-diagnosed asthma, bronchitis, and airways obstruction (total respiratory morbidity [TRM]) in Winnipeg in 1988 and 1992, using place of residence to divide people into quintiles according to average family income. Physician office visits, hospitalizations, and consultation referrals were each examined. Three age groups: 0 to 14 yr, 15 to 34 yr, and > or = 35 yr were studied. The prevalence of TRM was greater in low- than in high-income quintiles. Asthma prevalence was unrelated to income in the younger age groups; in the older group asthma was more common in low-income groups, but was less strongly related to income than was TRM. Asthma prevalence increased over the years studied, but the increase was not related to income level. There was some evidence of income-related diagnostic bias in that low-income patients were more likely to be labeled with a related diagnosis in addition to asthma than were high-income patients. Low-income patients had more physician contacts than did high-income patients. In terms of physician office visits, care continuity did not differ among income quintiles. Low-income quintiles had more hospitalizations than did high-income quintiles, and differences were larger than could be accounted for by diagnostic bias; asthma was probably more severe in low-income quintiles. High-income quintiles had more consultation referrals than did low-income quintiles.

A method of comparison for standardized rates of low-incidence events

The authors present an approximate but simple approach to comparing age-gender standardized rates of low-incidence events (mortality or morbidity) rates across several geographic areas. The presented method will be useful particularly when a person-level database, one that includes unique person identifiers, is not available. We specify conditions under which comparisons can be made without calculating empirical standard errors and worrying unduly about recurrent events. To compare indirectly standardized rates, only information on the size, the crude rate, and the standardized rate of the areas are needed. For comparing directly standardized rates, which requires stratum-specific rates, the method also requires stratum-specific total numbers of events and individuals but does not require person-level information. The proposed approach builds on previous work comparing rates using person-level data.

A population-based health information system

The authors introduce the Population Health Information System, its conceptual framework, and the data elements required to implement such a system in other jurisdictions. Among other innovations, the Population Health Information System distinguishes between indicators of health status (outcomes measures) and indicators of need for health care (socioeconomic measures of risk for poor health). The system also can be used to perform needs-based planning and challenge delivery patterns.

Stability and trends over 3 years of data

Because the health status of a population does not usually respond immediately to interventions, whether social or medical, the ability to analyze change over time is important. Therefore, patterns of change and stability in health status and health care use of Manitoba residents during a 3-year period from 1990 to 1992 were analyzed using the Population-based Health Information System. This article presents summary findings and discusses methodological and policy issues arising from the analyses. A small but significant decrease in premature mortality (the primary health status indicator) was observed in most regions of the province, but two remote, northern regions, those whose residents scored at high socioeconomic risk, remained distinguished for their poor health status. These "poor health" regions also had the highest contact rates with primary caregivers, raising questions about the role of the health care system in improving the health of the population. A persistent increase in surgery was observed in several regions, led by increases in outpatient surgery over and above increases in the elderly population and beyond substitution for inpatient procedures. This trend (not obvious before these analyses) is important as hospitals move to expand their outpatient facilities in response to restraints on inpatient care.

A population-based approach to monitoring adverse outcomes of medical care

A population-based approach to monitoring quality of care combining small-area analysis and outcomes assessment is proposed. While adverse outcomes due to poor surgical technique have long been targeted for quality-of-care review, in this study, giving similar attention to adverse outcomes produced by high rates of interventions is proposed. A population-based approach will strengthen traditional review efforts that currently begin and end at the hospital door. Excluded from these reviews have been questions such as the following: Should the procedure have been performed in the first place? Did the benefits outweigh the risks? Were there other patients not operated on who might have benefited more? Traditional approaches can identify less competent hospitals or practitioners: population-based approaches can identify the surgical enthusiasts who may pose equal risks to the populations of the areas they serve. Applying a population-based approach to review of coronary artery bypass graft surgery for Medicare patients in five cities in the United States demonstrates that at least as many deaths could have been prevented by decreasing surgical rates to the U.S. average as by improving the technical quality of care with which the procedure was performed. A similar population-based analysis of complications (as judged by re-admissions within 30 days of surgery) associated with hysterectomy across regions of Manitoba, Canada, is presented. In summary, negligent acts in the delivery of health care in institutions are rare and are difficult to detect because medicine is an inexact science and because adverse outcomes are more likely in high-risk patients, regardless of the quality of care. However, from a population perspective, adverse events are predictable, occur relatively frequently, and are directly related to the frequency of a population's exposure to surgical intervention. Efforts to improve quality of care could be made more effective by including the rates at which populations are exposed to treatments and the technical quality of care delivered.

Comparing standardized rates of events

This paper reviews issues associated with testing a null hypothesis of the equality of, and generating descriptive statistics for, standardized rates of events--recurrent or non-recurrent. The variance estimation for rates of surgical procedures, hospitalizations, and health care expenditures is discussed in the context of small area analysis. The proposed approach for estimating the variance of standardized rates is independent of assumptions about the underlying distribution of rates, is widely applicable, and seems preferable to approaches derived under special, but uncertain, parametric assumptions. A statistic is suggested based on person-level data, which allows comparing both rates of events and variation in rates between independent groups. The proposed statistic does not depend on the underlying unknown distribution of the events and does not require restrictive assumptions such as equal variances among the competing rates.

Crossover designs for clinical trials

I discuss three-period crossover designs for an efficient comparison of two test treatments with special application to clinical trials which often have many practical limitations. In this paper I specify a subset of three-period crossover designs so that the investigators are not left with the problematic two-period two-sequence design, should the trials be terminated after the second period. I show that there is a dramatic reduction in variability for estimating the direct and residual treatment effects in three-period designs compared to two-period designs. I also show that the universally optimal design with ABB and BAA sequences is unsuitable when a complex form of residual effects is suspected, such as the second-order residual effects or treatment by period interactions. The design with ABB, BAA, AAB, and BBA sequences is relatively robust to these uncertain model assumptions. I also discuss missing data problems and conclude that, even with a large proportion of missing values, the three-period design is far more efficient than the two-period design.

Differentiation of sugar assimilation characteristics and colony phenotypes in pathogenic and commensal oral candidal isolates

A comparison of sugar assimilation patterns has been made using 72 oral candidal isolates recovered from diseased and non-diseased patients. Significant differences were demonstrated between isolates recovered from diseased versus healthy mouths. In addition, significant changes in colony phenotype (switch frequency and morphologic predominance) were found to relate to predictive data generated from carbon source utilization data. These results suggest that biochemical properties and colony phenotypic characteristics may hold promise in predicting the behavior of oral candidal isolates in disease.