A head-to-head comparison of the EQ-5D-3L index scores derived from the two EQ-5D-3L value sets for China

OBJECTIVE: Two EQ-5D-3L (3L) value sets (developed in 2014 and 2018) co-exist in China. The study examined the level of agreement between index scores for all the 243 health states derived from them at both absolute and relative levels and compared the responsiveness of the two indices. METHODS: Intraclass correlations coefficient (ICC) and Bland–Altman plot were adopted to assess the degree of agreement between the two indices at the absolute level. Health gains for 29,403 possible transitions between pairs of 3L health states were calculated to assess the agreement at the relative level. Their responsiveness for the transitions was assessed using Cohen effect size. RESULTS: The mean (SD) value was 0.427 (0.206) and 0.649 (0.189) for the 3L(2014) and 3L(2018) index scores, respectively. Although the ICC value showed good agreement (i.e., 0.896), 88.9% (216/243) of the points were beyond the minimum important difference limit according to the Bland–Altman plot. The mean health gains for the 29,403 health transitions was 0.234 (3L(2014) index score) and 0.216 (3L(2018) index score). The two indices predicted consistent transitions in 23,720 (80.7%) of 29,403 pairs. For the consistent pairs, Cohen effective size value was 1.05 (3L(2014) index score) or 1.06 (3L(2018) index score); and the 3L(2014) index score only yielded 0.007 more utility gains. However, the results based on the two measures varied substantially according to the direction and magnitude of health change. CONCLUSION: The 3L(2014) and 3L(2018) index scores are not interchangeable. The choice between them is likely to influence QALYs estimations.