Validation and comparison of the psychometric properties of the EQ-5D-3L and EQ-5D-5L instruments in Greece

To validate and compare the psychometric properties of the EQ-5D-3L with the EQ-5D-5L classification systems in Greece. Participants (n = 2279) over 40 years old, sampled from the greater area of Athens using a multistage stratified quota sampling method, completed both EQ-5D versions, while information was also collected on socio-demographics and health-related characteristics. The EQ-5D-5L and EQ-5D-3L were evaluated in terms of agreement, ceiling effects, redistribution and inconsistency, informativity, and convergent and known-groups validity. The agreement between the EQ-5D-3L and EQ-5D-5L was high (ICC = 0.85). Ceiling effects decreased significantly in the EQ-5D-5L in all domains (P < 0.001), with "usual activities" (-21.4 %) and "self-care" (-20.1 %) showing the highest absolute and "anxiety/depression" the highest relative reduction (-32.46 %). Inconsistency was low (5.7 %). The increase in prevalence of problems was larger than the decrease in their severity, resulting in a lower mean health utility for the EQ-5D-5L. Overall absolute and relative informativity improved by 70.5 % and 16.4 %, respectively, in the EQ-5D-5L. Both instruments exhibited good convergent and known-groups validity, with evidence of a considerably better convergent performance and discriminatory ability of the EQ-5D-5L. Both EQ-5D versions demonstrated good construct validity and had consistent redistribution. The EQ-5D-5L system may be preferable to the EQ-5D-3L, as it exhibited superior performance in terms of lower ceiling effects, higher absolute and relative informativity, and improved convergent and known-groups validity efficiency.