Psychometric comparison of the standard EQ-5D to a 5 level version in cancer patients

OBJECTIVE: The objectives of this study were: 1) to determine whether expanding the number of levels (ie, response categories) on the standard 3 level EQ-5D (EQ-5D-3L) to 5-levels (EQ-5D-5L) would improve the descriptive richness and ability of the measure to discriminate among different levels of health, and 2) to examine the psychometric properties of each EQ-5D version in patients with cancer. METHODS: U.S.-based cancer patients self-assessed their health using EQ-5D-3L and EQ-5D-5L. These versions were compared in terms of ceiling effects, convergent validity based on correlations with ECOG performance status and FACT-G, discriminative ability using Rasch analysis, and informational richness using Shannon's Evenness Index (J'). RESULTS: A ceiling effect was observed among a greater proportion of respondents to EQ-5D-3L, n = 74/424 (17%), compared with EQ-5D-5L, n = 47/424 (11%). Within the midlevel of EQ-5D-3L (some problems), substantial partitioning of the sample into the 3 nonextreme levels of the EQ-5D-5L was observed across dimensions. EQ-5D-5L demonstrated a trend towards slightly stronger correlations with ECOG performance status compared with EQ-5D-3L for all dimensions of health, ie, r_s (5L/3L): r_mobility = 0.38/0.31; r_self-care = 0.35/0.31; r _{usual activities} = 0.55/0.47; r_{pain/discomfort} = 0.43/0.37; r_{anxiety/depression} = 0.23/0.16; r _{crude summary score} = 0.56/0.49. EQ-5D-5L demonstrated a greater relative efficiency and ability to discriminate different levels of health. Informational richness and evenness of EQ-5D-5L was slightly higher (J'5L = 0.75) than EQ-5D-3L (J'3L = 0.69). CONCLUSION: Evidence supported the validity of both EQ-5D-3L and EQ-5D-5L in cancer. However, results suggest a 5-level classifier system has less ceiling effect and greater discriminative ability with potentially more power to detect differences between groups compared with EQ-5D-3L.