The responsiveness of EQ-5D utility scores in patients with depression: A comparison with instruments measuring quality of life, psychopathology and social functioning

Introduction: The EQ-5D provides preference weights (utilities) for health-related quality of life to be used for calculating quality-adjusted life years (QALYs) in cost-utility analysis. The aim of this study was to compare differences in EQ-5D utility scores with differences in quality of life, psychopathology, and social functioning scores. Methods: In an observational longitudinal cohort study, EQ-5D utilities (EQ visual analogue scale (EQ VAS), EQ-5D indices of the United Kingdom (EQ-5D index-UK) and Germany (EQ-5D index-D)) were compared with scores of the WHOQOL-BREF, CGI, and GAF at baseline and at 18 months (N = 104). The patients' health status at follow-up was categorized as worse, stable, or better using the EQ-5D transition question (patient-based anchor) and the Bech-Rafaelsen melancholy scale (clinician-based anchor). Effect sizes (ES) were used to compare differences in scores within each group over time; regression analysis was used to derive meaningful difference scores in health status associated with a shift from stable to better health status. Results: The most responsive instrument was the CGI (patient-based anchor: ES=vertical bar 0.98 vertical bar; clinician-based anchor: ES=vertical bar 1.35 vertical bar); responsiveness was large in EQ VAS (patient-based anchor: ES=vertical bar 0.84 vertical bar; clinician-based anchor: ES=vertical bar 1.19 vertical bar), but rather small to mediumforEQ-5D index-UK(patient-based anchor: ES=vertical bar 0.55 vertical bar; clinician-based anchor: ES=vertical bar 0.65 vertical bar)and EQ-5D index-D (patient-based anchor: ES=10.411; clinician-based anchor: ES=vertical bar 0.45 vertical bar). Compared with the other instruments, the shift to a better health status was smaller if elicited by the EQ-5D indices. Discussion: Both EQ-5D indices were less responsive and need larger patient samples to detect meaningful differences compared with EQ VAS and the other instruments. (C) 2007 Elsevier B.V. All rights reserved.