Assessing the construct validity and responsiveness of Preference-Based Measures (PBMs) in cataract surgery patients

Purpose The validity and responsiveness of the EQ-5D-3L in visual conditions has been questioned, inspiring development of a vision 'bolt-on' domain (EQ-5D-3L + VIS). Developments in preference-based measures (PBM) also includes the EQ-5D-5L and the ICECAP-O capability wellbeing measure. This study aimed to examine the construct validity and responsiveness of the EQ-5D-3L, EQ-5D-5L, EQ-5D-3L + VIS and ICECAP-O in cataract surgery patients for the first time, to inform choice of PBM for economic evaluation in this population. Methods The analyses used data from the UK Predict-CAT cataract surgery cohort study. PBMs and the Cat-PROM5 [a validated measure of cataract quality of life (QOL)] were completed before surgery and 4-8 weeks after. Construct validity was assessed using correlations and known-group differences evaluated using regression. Responsiveness was evaluated using effect sizes and analysis of variance to compare change scores between groups, defined by patient-reported and clinical outcomes. Results The sample comprised 1315 patients at baseline. No PBMs were associated with visual acuity and only the ICECAP-O (Spearman's rs = - 0.35), EQ-5D-3L + VIS (rs = - 0.42) and EQ-5D-5L (Value Set for England rs = - 0.31) correlated at least moderately with the Cat-PROM5. Effect sizes of change were consistently largest for the EQ-5D-3L + VIS (range 0.34-0.41), followed by the ICECAP-O (range 0.20-0.34). Results indicated no improvement in responsiveness using the EQ-5D-5L (range 0.13-0.16) compared to the EQ-5D-3L (range 0.17-0.20). Conclusions Whilst no PBMs comprehensively demonstrated evidence of construct validity and responsiveness in cataract surgery patients, the ICECAP-O was the most responsive generic PBM to improvements in QOL. Surprisingly the EQ-5D-5L was not more responsive than the EQ-5D-3L in this setting.