Measures of relative importance for health-related quality of life
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In health-related quality of life (HRQOL) studies, data are often collected on multiple domains for two or more groups of study participants. Quantitative measures of relative importance, which are used to rank order the domains based on their ability to discriminate between groups, are an alternative to multiple tests of significance on the group differences. This study describes relative importance measures based on logistic regression (LR) and multivariate analysis of variance (MANOVA) models.
Relative importance measures are illustrated using data from the Manitoba Inflammatory Bowel Disease (IBD) Cohort Study. Study participants with self-reported active (n = 244) and inactive (n = 105) disease were compared on 12 HRQOL domains from the Inflammatory Bowel Disease Questionnaire (IBDQ) and Medical Outcomes Study 36-item Short-Form (SF-36) Questionnaire.
All but two relative importance measures ranked the IBDQ bowel symptoms and emotional health domains as most important.
MANOVA-based importance measures are recommended for multivariate normal data and when group covariances are equal, while LR measures are recommended for non-normal data and when the correlations among the domains are small. Relative importance measures can be used in exploratory studies to identify a small set of domains for further research.
KeywordsDiscriminant analysis Health-related quality of life Inflammatory bowel disease Logistic model Multivariate analysis Relative importance
Adjusted discriminant ratio coefficient
Adjusted Pratt’s Index
Descriptive discriminant analysis
Discriminant ratio coefficient
Health-related quality of life
Inflammatory bowel disease
Inflammatory Bowel Disease Questionnaire
Multivariate analysis of variance
Ordinary least squares
Rescaled relative weight
Standardized discriminant function coefficient
36-Item Short Form Questionnaire
Standardized logistic regression coefficient
This research was supported by a Canadian Institutes of Health Research (CIHR) Vanier Graduate Scholarship to the first author, funding from the Manitoba Health Research Council and a CIHR New Investigator Award to the second author, funding from a Crohn’s and Colitis Foundation of Canada Research Investigator Award and the Bingham Chair in Gastroenterology to the last author and funding from a CIHR Operating Grant to the research team.
Conflict of interest
Dr. Lix has received funding from Amgen in the form of an unrestricted research grant. In the past year, Dr. Bernstein has received consulting fees from Abbott Canada and an unrestricted educational grant from Axcan Pharma.
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