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Biomedical subjects

J A Kopec

Publications and source records attributed to J A Kopec.

14 recordsLinked to original sources
PubMed2002

Measuring the health burden of chronic disease and injury using health adjusted life expectancy and the Health Utilities Index.

OBJECTIVES: To estimate the burden of illness from chronic disease and injury using a population based health survey, which contains both measures of chronic disease and a utility based health related quality of life (HRQOL) measure. DESIGN: An adapted Sullivan method was used to calculate cause deleted health adjusted life expectancies for chronic conditions. SETTING: Ontario, Canada, 1996/97. SUBJECTS: The 1996/97 Ontario Health Survey (n=35 527) was used to estimate the prevalence of chronic conditions. A cause deleted approach was used to estimate the impact of these conditions on the Health Utilities Index (HUI). Cause deleted probabilities of dying were derived with the cause eliminated life table technique and death data from vital statistics for Ontario 1996/97 (n=156 610). RESULTS: Eliminating cardiovascular disease and cancer will cause an "expansion of morbidity", while eliminating mental conditions and musculosketal disorders will result in a "contraction of morbidity". The HUI score varies depending on chronic condition, age, and sex-most of which were assumed not to vary in previous summary measures of population health. CONCLUSIONS: Health adjusted life expectancy estimated for chronic conditions using a utility based measure of health related quality of life from population health surveys addresses several limitations of previous studies that estimate the burden of disease using either a categorical measure of disability or expert opinion and related epidemiological evidence.

Adolescent↗
PubMed2001

Cross-cultural comparisons of health status in Canada using the Health Utilities Index.

OBJECTIVE: The purpose of this study was to examine the differences in health status, as measured by the Health Utilities Index (HUI), among seven cultural groups in Canada defined by place of birth and language. DESIGN: The study analysed cross-sectional data from the National Population Health Survey conducted by Statistics Canada in 1994-95. RESULTS: Age-standardized prevalence of dysfunction, defined as HUI < 0.83, varied from 12.7% in English-speaking immigrants to 17.8% in French-speaking Canadians. Considerable differences between the groups were found in the reporting of pain, emotional function, and cognitive function. The variation in HUI scores across the cultural groups could not be explained by differences in socioeconomic status and self-reported chronic conditions. CONCLUSIONS: Although the healthy immigrant effect is probably responsible for some of the variation in health status among cultural groups in Canada, considerable differences exist within the immigrant and Canadian-born populations. Cultural factors may have a substantial effect on the reporting of pain and mental health problems. Further studies are needed to determine the cross-cultural validity of the HUI.

Canada↗
PubMed2001

Can the health utilities index measure change?

BACKGROUND: The Health Utilities Index (HUI) is a multidimensional, preference-weighted measure of health status. It comprises eight health attributes, aggregated into a single utility score. OBJECTIVES: The purpose of the study was to investigate the ability of the HUI to detect changes in health status in a general population cohort. RESEARCH DESIGN: Health status changes were analyzed in the full cohort and in persons who were diagnosed with chronic conditions, hospitalized, or became restricted in daily activities. SUBJECTS: To assess responsiveness, longitudinal data was used from the National Population Health Survey conducted in Canada in 1994 - 1995 and 1996 - 1997. We used cross-sectional data from the 1996 sample to classify chronic conditions into mild, moderate, and severe. MEASURES: Two measures of responsiveness were calculated: Standardized Response Mean (SRM) and Sensitivity Coefficient (SC). The HUI was compared with a global health index-the Self-Rated Health (SRH) scale. RESULTS: HUI scores improved between the two NPHS cycles in all age-sex groups, except men 65 years of age and older. Among the respondents who remained free of chronic conditions, improvements were seen primarily in the cognitive and emotional domains. The HUI deteriorated among persons who were diagnosed between the two cycles with a severe chronic condition, were hospitalized, or became restricted in activity, but not in those diagnosed with a moderate condition. The SRMs were generally smaller for the HUI compared with the SRH. CONCLUSIONS: The HUI responds to changes in health status associated with serious chronic illnesses. However, changes in the HUI do not always coincide with changes in self-reported health. Properties of the HUI scales require further study.

Adolescent↗
PubMed2000

The use of the Tobit model for analyzing measures of health status.

Self-reported health status is often measured using psychometric or utility indices that provide a score intended to summarize an individual's health. Measurements of health status can be subject to a ceiling effect. Frequently, researchers want to examine relationships between determinants of health and measures of health status. Regression methods that ignore the presence of a ceiling effect, or of censoring in the health status measurements can produce biased coefficient estimates. The Tobit regression model is a frequently used tool for modeling censored variables in econometrics research. The authors carried out a Monte-Carlo simulation study to contrast the performance of the Tobit model for censored data with that of ordinary least squares (OLS) regression. It was demonstrated that in the presence of a ceiling effect, if the conditional distribution of the measure of health status had uniform variance, then the coefficient estimates from the Tobit model have superior performance compared with estimates from OLS regression. However, if the conditional distribution had non-uniform variance, then the Tobit model performed at least as poorly as the OLS model.

Adult↗
PubMed1998

Occupational role performance in persons with back pain.

PURPOSE: Back pain is a major cause of work disability but there is little data on the impact of back pain among persons who are working. The purpose of this study was to develop a measure of occupational role performance for individuals with back pain and to examine its relationship with sociodemographic and work-related factors. METHOD: Item analysis and reduction resulted in a short, eight-item Occupational Role Questionnaire (ORQ) consisting of two scales, a productivity scale and a satisfaction with work scale. The scales had good internal consistency and correlated as expected with the Roland and Morris Disability Scale. RESULTS: In a multivariate logistic model, significant negative effects on work satisfaction were observed for age 30-39 years relative to age 50+, having a job that required lifting, and the level of disability. CONCLUSION: The ORQ may have applications in studying the consequences of back pain and other chronic conditions in the workplace.

Adult↗
PubMed1996

The Quebec Back Pain Disability Scale: conceptualization and development.

The Quebec Back Pain Disability Scale is a new measure of functional disability for patients with back pain. Functional disability was operationalized in terms of perceived difficulty associated with simple physical activities. The content of the scale was developed in several stages, including a literature review, two studies seeking the opinions of patients and experts, pilot testing, and a large, longitudinal study of back pain patients. Forty-eight disability items were extensively studied using standard methods such as test-retest reliability, item-total correlations, and factor analysis, as well as modern techniques based on item response theory. Items that were highly effective in discriminating between different levels of disability were selected for the final, reduced scale. The scale has 20 items, representing six empirically derived categories of activities affected by back pain. Measurement properties of this instrument have been previously discussed.

Activities of Daily Living↗
PubMed1995

Functional disability scales for back pain.

Functional disability scales for back pain are reviewed for content and measurement properties, concentrating on five widely used questionnaires. Current methodological issues in functional assessment also are discussed.

Disability Evaluation↗
PubMed1995

The Quebec Back Pain Disability Scale. Measurement properties.

STUDY DESIGN: The Quebec Back Pain Disability Scale is a 20-item self-administered instrument designed to assess the level of functional disability in individuals with back pain. The scale was administered as part of a larger questionnaire to a group of 242 back pain patients. Follow-up data were obtained after several days and after 2 to 6 months. OBJECTIVES: The goal of this study was to determine whether the Quebec scale is a reliable, valid, and responsive measure of disability in back pain, and to compare it with other disability scales. SUMMARY OF BACKGROUND DATA: A number of functional disability scales for back pain are being used, but their conceptual validity is uncertain. Unlike most published instruments, the Quebec scale was constructed using a conceptual approach to disability assessment and empirical methods of item development, analysis, and selection. METHODS: The authors calculated test-retest and internal consistency coefficients, evaluated construct validity of the scale, and tested its responsiveness against a global index of change. Direct comparisons with the Roland, Oswestry, and SF-36 scales were carried out. RESULTS: Test-retest reliability was 0.92, and Cronbach's alpha coefficient was 0.96. The scale correlated as expected with other measures of disability, pain, medical history, and utilization variables, work-related variables, and socio-demographic characteristics. Significant changes in disability over time, and differences in change scores between patients that were expected to differ in the direction of change, were found. CONCLUSIONS: The Quebec scale can be recommended as an outcome measure in clinical trials, and for monitoring the progress of individual patients participating in treatment or rehabilitation programs.

Adolescent↗
PubMed1995

Concepts of disability: the Activity Space Model.

This paper describes a new conceptual framework for functional assessment, the Activity Space Model (ASM). According to this model, functional impairments may lead to restrictions in an individual's activity space, a multidimensional space that represents human potential for activity. For each elementary ability, restrictions in the corresponding dimension of the activity space can be evaluated by deriving a difficulty curve that depicts the relationship between the level of performance and the psychophysical cost of activity. The effect of disease on daily functioning is explained in terms of a tradeoff between the psychophysical cost and the value of each act of behavior to the disabled individual. These two constructs are measured on the same scale and expressed in units of difficulty. The location of each task within the activity space in relation to the difficulty curve determines whether it will be performed or avoided at a given point in time. The ASM has both theoretical and practical implications. It offers a new, integrated perspective on disability and suggests new strategies for developing and evaluating functional assessment measures.

Disability Evaluation↗
PubMed1993

Randomized discontinuation trials: utility and efficiency.

The randomized discontinuation trial (RDT) is a two-phase trial. In phase I all patients are openly treated with the medication being evaluated. In phase II, those who have responded are randomly assigned to continue the same treatment or switch to placebo. Usually, non-compliers and "adverse reactors" identified in phase I are excluded from phase II. To investigate the value of this design, we reviewed the advantages and limitations of discontinuation studies, and compared the RDT design to the classic randomized clinical trial design in terms of clinical utility and efficiency (sample size). A computer model was used to study the efficiency of the two designs under a broad range of assumptions. The RDT design is particularly useful in studying the effect of long-term, non-curative therapies, especially when the clinically important effect is relatively small, and the use of placebo should be minimized for ethical or feasibility reasons. However, its use is limited if the objective of an investigation is to estimate the magnitude of absolute treatment effects and toxic effects in the source population, or to evaluate a potentially curative treatment. Our results indicate that selecting responders prior to randomization has a very strong effect on the relative efficiency of the trial. Further improvement may be achieved by excluding non-compliers and adverse reactors. Under the assumptions tested in our model, the sample size required in phase II of an RDT was only 20-50% of that in a classic trial.

Computer Simulation↗
PubMedDate not supplied

Measuring population health: correlates of the Health Utilities Index among English and French Canadians.

This study used cross-sectional data from the 1994/95 National Population Health Survey (NPHS) in Canada. The objective of the study was to examine the relationship between several established correlates of health status in the general population and the Health Utilities Index (HUI), a multi-dimensional, preference-based measure of health status. Analyses were carried out separately for the English-speaking (n = 9,853) and French-speaking (n = 1,519) respondents. The index correlated strongly with self-ratings of health status and functional disability and varied as expected according to age, sex, and income. Subjects classified to different categories of chronic conditions reported different levels of health, as predicted. The HUI was also associated with the use of drugs and recent history of hospitalization. No major differences in the findings were observed between the two cultural groups. The results should be treated with caution due to the cross-sectional design and other methodological limitations of the study.

Activities of Daily Living↗