Psychometric Performance of a New Condition-Specific Preference-Weighted Measure, Vision Impairment in Low Luminance-Utility Index, and EQ-5D-5L in Patients With Age-Related Macular Degeneration: A MACUSTAR Study Report

Objectives The Vision Impairment in Low Luminance-Utility Index (VILL-UI) is a novel preference-weighted measure for use in patients with age-related macular degeneration (AMD). No evidence exists on its psychometric performance nor its performance in comparison with the generic preference-weighted measure, EQ-5D-5L, commonly used in economic evaluation. This study compares the psychometric performance of VILL-UI with EQ-5D-5L in patients with AMD. Methods Assessments of feasibility, convergent/divergent validity, and known-group validity of VILL-UI and EQ-5D-5L are undertaken using MACUSTAR data at baseline, 12, 24, and 36 months. Analyses are undertaken separately using UK and German preference weights for both measures. Results The sample with complete responses (n = 586) had mean age 71.9 years (standard deviation 6.9), 65.2% women, with predominantly intermediate AMD (87.2%). VILL-UI and EQ-5D-5L are feasible for completion, although VILL-UI has fewer usable responses due to its response options (baseline 89% vs 100%). EQ-5D-5L has high ceiling effects, with around one-third of participants reporting the best health state compared with under 8% for VILL-UI. Convergent validity between EQ-5D-5L and VILL-UI utilities and dimensions in which a relationship is expected is low, with divergent validity demonstrated where expected. VILL-UI detected statistically significant differences in known groups for visual acuity, visual function, and AMD stage across most time points, with little evidence of known-group validity for EQ-5D-5L. Conclusions VILL-UI is appropriate for use in future AMD studies to inform economic evaluation. VILL-UI has superior performance to EQ-5D-5L for known-group validity and has fewer ceiling effects but has fewer usable responses.