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K C Carriere

Publications and source records attributed to K C Carriere.

At least 19 recordsLinked to original sources
PubMed2001

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.

Bone Marrow Transplantation↗
PubMed2001

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.

Adult↗
PubMed2000

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.

Adult↗
PubMed2000

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.

Animals↗
PubMed2000

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.

Adolescent↗
PubMed1999

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.

Adolescent↗
PubMed1999

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.

Community Health Planning↗
PubMed1999

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.

Acute Disease↗
PubMed1999

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.

Adult↗
PubMed1999

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.

Adolescent↗
PubMed1998

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.

Animals↗
PubMed1998

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.

Canada↗
PubMed1997

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.

Adult↗
PubMed1997

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.

Coronary Angiography↗
PubMed1997

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.

Adolescent↗
PubMed1995

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.

Canada↗
PubMed1995

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.

Adolescent↗