Comparing the standard EQ-5D three-level system with a five-level version

Objective: The aim of this study is a head-to-head comparison of the performance of the three-level EQ-5D (3L) and a newly developed five-level version (5L). Methods: Eighty-two respondents valued 15 standardized disease descriptions and their own health on three response scales (3L, 5L, and visual analog scale [VAS]) for all five EQ-5D dimensions. Performance was studied in terms of feasibility, face validity, redistribution properties, ordinality, convergent validity, discriminatory power, and test-retest and interobserver reliability. Results: The majority of participants judged 5L as the preferred system in terms of feasibility (76%) and face validity (75%). In total, 1.1% of responses were inconsistent. Ordinality of 5L was confirmed in all cases. Convergent validity of 3L-VAS (range: 0.88-0.99) and 5L-VAS (0.90-0.99) were high and about equal. Discriminatory power (informativity) improves considerably with 5L without loss of Evenness. Interobserver reliability (0.49 vs. 0.57) and test-retest reliability (0.52 vs. 0.69) were higher in 5L. Conclusions: The EQ-5D five-level version appears a valid and reliable extension of the three-level system. The new 5L system is particularly useful for describing mild health problems and monitoring population health.