Measurement properties of the EQ-5D-5L compared to the EQ-5D-3L in psoriasis patients.

Abstract

A cross-sectional survey was carried out at an academic dermatology clinic in Hungary. Psoriasis patients completed the EQ-5D-3L, EQ-5D-5L and Dermatology Life Quality Index (DLQI) questionnaires, and Psoriasis Area and Severity Index (PASI) was assessed. The UK value sets were used to calculate the 3L and 5L index scores. We tested the feasibility, ceiling effect, redistribution properties, the level of inconsistency and informativity (Shannon and Shannon Evenness indices). Spearman's rank-order correlations were performed between EQ-5D, EQ VAS, DLQI and PASI scores. Known-groups validity was evaluated by comparing age groups, clinical subtypes and treatment groups. Mean age of the 238 patients was 47years, and 36.6% of them received biological therapy. Mean EQ-5D index score was 0.77 (SD: 0.26) with the 3L and 0.84 (SD: 0.19) with the 5L. The overall ceiling effect decreased from 37.1 (3L) to 32.9% (5L). Shannon index improved significantly for most dimensions, but Shannon Evenness index improved only in three dimensions. Compared to the 3L, the 5L version confirmed a better convergent validity with PASI, but not with the DLQI. Known-groups validity was equally demonstrated both for the 5L and 3L. The EQ-5D-5L seems to improve measurement properties by reducing ceiling effects, strengthening correlations with PASI and improving informativity. Follow-up studies are needed to test responsiveness and reliability in psoriasis.