What Age is Appropriate for Self-Reporting EQ-5D-Y-3L? Chinese Insights from a Sample of Children Aged 6-11 years.

OBJECTIVE: This study aims to explore the minimum age threshold for children to self-complete the EQ-5D-Y-3L in China through mixed-methods, providing evidence on the self-report validity from the perspective of respondents. METHODS: A consecutive sample of children aged 6-11 years was recruited from four schools in Ningxia province, China. Participants completed EQ-5D-Y-3L and were invited to participated in cognitive interview. Mixed-methods, including both qualitative and quantitative methods we used. Qualitative data were systematically derived from coding analysis of cognitive interview outcomes and subsequently transformed into quantitative data based on Tourangeau's four-stage response model. Quantitative analyses included chi-square test for age-response problem associations, Cochran-Armitage trend test, and logistic regression for trend analysis. RESULTS: A total of 906 children completed the survey (mean age 8.5 years, 52.1% male), with 650 completing cognitive interviews. Systematic health conceptualization mapping with EQ-5D-Y-3L constructs emerged at children aged 9 years or older, with higher consensus in item-health relevance judgment attribution. A significant association was observed between age and response issues (P<0.001), with the prevalence of response problems demonstrating a statistically significant decreasing trend as age increased (Z=-5.37, P<0.001). Each year of age reduced response problem risk by 26% (OR=0.740, 95% CI [0.662, 0.828], P<0.001). CONCLUSION: Children under 9 years demonstrated an underdeveloped health framework and complex cognitive deviations in item-health relevance assessment, necessitating cautious interpretation of self-reported EQ-5D-Y-3L. While self-report validity becomes generally acceptable from 9 years old, age-specific response variations persist, requiring context-specific applicability evaluation.