Effect of External Variables on the Performance of the Geriatric Comorbidity Score Derived from Prescription Claims in t
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ORIGINAL RESEARCH ARTICLE
Effect of External Variables on the Performance of the Geriatric Comorbidity Score Derived from Prescription Claims in the Community-Dwelling Elderly Sarah-Gabrielle Be´land • Cara Tannenbaum • Thierry Ducruet • Michel Pre´ville • Djamal Berbiche Yola Moride
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Published online: 30 October 2012 Ó Springer International Publishing Switzerland 2012
Abstract Background Comorbidity scores based on medical or prescription claims data are frequently used to control for confounding in pharmacoepidemiological studies. Performance of such scores in predicting the risk of death in community-dwelling elderly adults may be compromised by the absence of mental health and socioeconomic characteristics not captured in claims data. Objective The aim of the study was to assess the impact of adding mental health status and sociodemographic characteristics to the Geriatric Comorbidity Score (GCS), a score derived from prescription claims data in the Quebec community-dwelling elderly population. Methods We used the cohort study from the longitudinal Quebec Seniors’ Health Survey (n = 1,494) conducted between 2005 and 2006. For each participant, we obtained mental health and socioeconomic characteristics through validated questionnaires, which we linked with the medical and prescription claims databases of the Quebec Health Insurance Agency [Re´gie de l’assurance maladie du
S.-G. Be´land C. Tannenbaum T. Ducruet Y. Moride (&) Faculty of Pharmacy, University of Montreal, P.O. Box 6128, succ. Centre-ville, Montreal, QC H3C 3J7, Canada e-mail: [email protected] S.-G. Be´land T. Ducruet Y. Moride Pharmacoepidemiology Unit, Research Centre of the University of Montreal Hospital Centre (CRCHUM), Montreal, QC, Canada C. Tannenbaum Research Centre, University of Montreal Geriatrics Institute, Montreal, QC, Canada M. Pre´ville D. Berbiche Charles LeMoyne Hospital Research Centre, University of Sherbrooke, Longueuil, QC, Canada
Que´bec (RAMQ)]. The main study outcome was death within 1 year, ascertained using the Quebec death registry. The GCS was calculated from prescription claims data, with the c statistic as a measure of performance. Using backward stepwise selection, external variables (marital status, region, family income, social support, daily hassles, perceived physical and mental health status, presence of mental health disorders) were added to the logistic regression model and the marginal effect assessed by comparing the c statistic with and without each covariate. Results Over 1 year, 77 deaths (5.15 %) were reported. The c statistic for the GCS was calculated as 0.67 (95 % confidence interval 0.64, 0.70). Addition of sex and age to the score yielded a 2.4 % increase. The variable with the greatest impact on the c statistic was marital status (6.1 % increase). Though important contributors, social support and perceived mental health status did not significantly improve performance of the score. Conclusions While sex, age and marital status significantly improved performance of a predic
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