Estimation of minimal clinically important difference in EQ-5D visual analog scale score after pulmonary rehabilitation in subjects with COPD

Abstract

Background: The effect of pulmonary rehabilitation (PR) on the EuroQol Group's 5-dimension questionnaire (EQ-5D) in COPD has been poorly investigated. In addition, conflicting results were reported about the visual analog scale component of EQ-5D (EQ-VAS). The purpose of this study was to evaluate the responsiveness of EQ-VAS to PR and its relationship with clinical and functional parameters in subjects with COPD, as well as to define the minimal clinically important difference (MCID) estimate for the EQ-VAS after PR.

Methods: A total of 468 in-patients with stable moderate-to-severe COPD, allocated to a 3-wk PR program, were retrospectively evaluated. EQ-VAS was assessed before and after PR, and its relationship with baseline pulmonary function, changes in 6-min walk test, and baseline, and transitional dyspnea index (BDI/TDI) after PR were evaluated. Using an anchor-based approach and receiver operating characteristic curves, the EQ-VAS change cutoff that identified subjects achieving the known MCID for TDI after PR was identified.

Results: Four hundred and thirty-nine subjects (94%, mean FEV1 55.3% predicted) completed pre- and post-PR EQ-VAS scores. After PR, EQ-VAS increased from 58 ± 17 to 72 ± 15 (ΔEQ-VAS 14 ± 12, P < .001). ΔEQ-VAS was negatively related to baseline FEV1 (r = -0.32, P < .001) and positively to TDI (r = 0.50, P < .001) and 6-min walk distance (r = 0.46, P < .001) changes. Receiver operating characteristic curves identified an EQ-VAS change cutoff of 8 as the best discriminating value to identify the MCID for TDI (0.78 sensitivity and 0.81 specificity; area under curve: 0.845, P < .001).

Conclusions: Our study shows that, in in-patients with stable moderate-to-severe COPD, EQ-VAS is a valid and reliable tool to assess the responsiveness to PR, with an estimated MCID of 8 points. The EQ-VAS can be a practical alternative to more time-consuming measures of health-related quality of life.

Keywords: COPD; EuroQol; VAS; pulmonary rehabilitation.