Psychometric Performance Comparison of the Adapted versus Original Versions of the EQ-5D-Y-3L and -Y-5L in Proxy Respondents for 2- to 4-Year-Olds

Introduction Few preference-weighted instruments are available to measure health-related quality of life in young children (2–4 years of age). The EQ-5D-Y-3L and EQ-5D-Y-5L were recently modified for this purpose. Objective The aim of this study was to test the psychometric properties of these adapted versions for use with parent proxies of children aged 2–4 years and to compare their performance with the original versions. It was hypothesised that the adapted instrument wording would result in improved psychometric performance. Methods Survey data of children aged 2–4 years were obtained from the Australian Paediatric Multi-Instrument Comparison study. Distributional and psychometric properties tested included feasibility, convergence, distribution of level scores, ceiling effects, known-group validity (Cohen’s D effect sizes for prespecified groups defined by the presence/absence of special healthcare needs [SHCNs]), test-retest reliability (intraclass correlation coefficients [ICCs]), and responsiveness (standardised response mean [SRM] effect sizes for changes in health). Level sum scores were used to provide summary outcomes. Supplementary analysis using utility scores (from the Swedish EQ-5D-Y-3L value set) were conducted for the adapted and original EQ-5D-Y-3L, and no value sets were available for the EQ-5D-Y-5L. Results A total of 842 parents of children aged 2–4 years completed the survey. All instruments were easy to complete. There was strong convergence between the adapted and original EQ-5D-Y-3L and EQ-5D-Y-5L. The adapted EQ-5D-Y-3L and adapted EQ-5D-Y-5L showed more responses in the severe levels of the five EQ-5D-Y dimensions, particularly in the usual activity and mobility dimensions (EQ-5D-Y-5L: mobility level 1: adapted n = 478 [83%], original n = 253 [94%]; mobility level 4/5: adapted n = 17 [2.9%], original n = 4 [1.5%)]). The difference in the distribution of responses was more evident in children with SHCNs. Assessment of known-group validity showed a greater effect size for the adapted EQ-5D-Y-3L and adapted EQ-5D-Y-5L compared with the original instruments (EQ-5D-Y-5L: adapted Cohen’s D = 1.01, original Cohen’s D = 0.83) between children with and without SHCNs. The adapted EQ-5D-Y-3L and adapted EQ-5D-Y-5L showed improved reliability at 4-week follow-up, with improved ICCs (EQ-5D-Y-5L: adapted ICC = 0.83, original ICC = 0.44). The responsiveness of all instruments moved in the hypothesised direction for better or worse health at follow-up. Probability of superiority analysis showed little/no differences between the adapted and original EQ-5D-Y-3L and EQ-5D-Y-5L. Supplementary psychometric analysis of the adapted and original EQ-5D-Y-3L using utilities showed comparable findings with analyses using level sum scores. Conclusions The findings suggest improved psychometric performance of the adapted version of the EQ-5D-Y-3L and EQ-5D-Y-5L in children aged 2–4 years compared with the original versions.