The EQ-5D-5L health status questionnaire in COPD: validity, responsiveness and minimum important difference

Background The EQ-5D, a generic health status questionnaire that is widely used in health economic evaluation, was recently expanded to the EQ-5D-5L to address criticisms of unresponsiveness and ceiling effect. Aims To describe the validity, responsiveness and minimum important difference of the EQ-5D-5L in COPD. Methods Study 1: The validity of the EQ-5D-5L utility index and visual analogue scale (EQ-VAS) was compared with four established disease-specific health status questionnaires and other measures of disease severity in 616 stable outpatients with COPD. Study 2: The EQ-5D-5L utility index and EQ-VAS were measured in 324 patients with COPD before and after 8 weeks of pulmonary rehabilitation. Distribution and anchor-based approaches were used to estimate the minimum important difference. Results There were moderate-to-strong correlations between utility index and EQ-VAS with disease-specific questionnaires (Pearson's r=0.47-0.72). A ceiling effect was seen in 7% and 2.6% of utility index and EQ-VAS. Utility index decreased (worsening health status) with indices of worsening disease severity. With rehabilitation, mean (95% CI) changes in utility index and EQ-VAS were 0.065 (0.047 to 0.083) and 8.6 (6.5 to 10.7), respectively, with standardised response means of 0.39 and 0.44. The mean (range) anchor estimates of the minimum important difference for utility index and EQ-VAS were 0.051 (0.037 to 0.063) and 6.9 (6.5 to 8.0), respectively. Conclusions The EQ-5D-5L is a valid and responsive measure of health status in COPD and may provide useful additional cost-effectiveness data in clinical trials.