Determining the Content Validity of the EQ-5D-5L, EQ-5D-Y-3L, and CHU9D Instruments for Assessing Generic Child and Adolescent Health-Related Quality of Life: A Qualitative Study.

Background: Health technology assessment agencies typically recommend generic measures of health to generate quality-adjusted life-years. Most agencies provide recommendations on which measure to use for adults, whereas few make recommendations for children. Two widely used preference-weighted measures of child and adolescent health that have evidence of good psychometric performance are the EQ-5D-Y-3L and the Child Health Utility 9D Index (CHU9D). The EQ-5D-5L has also been used to assess adolescent health. However, evidence on their content validity-a core measurement property-is limited. The objective of this study was to explore the content validity of the EQ-5D-5L, EQ-5D-Y-3L, and CHU9D measures, including their relevance, comprehensiveness, and comprehensibility.

Methods: We assessed the content validity of the EQ-5D-5L, EQ-5D-Y-3L, and CHU9D using online semi-structured cognitive interviews in the UK. Participants were asked to comment on the relevance, comprehensibility, and comprehensiveness of the measures, including response options, recall period, and completion instructions. Interviews were informed by a topic guide. Purposive sampling allowed for appropriate breadth in the sample, with variation in gender, and presence of health conditions, disease, or disability. Interviews were recorded and transcribed verbatim before thematic content analysis.

Results: In total, we conducted 49 interviews between August 2022 and June 2023: 21 children/adolescents aged 8-17 years and 28 parents/guardians of children aged 4-17 years. The mean duration of the interviews was 45 min. Relevance was broadly supported, but issues were identified. Comprehensibility was inconsistent on some items, and participants expressed difficulty with grouped items (e.g., 'anxiety/depression'). Participants had difficulty distinguishing qualitatively between some response options (e.g., 'a little bit/a bit'). Some participants noted that instrument comprehensiveness was insufficient.

Conclusions: Although the content of the EQ-5D-5L, EQ-5D-Y-3L, and CHU9D was broadly supported, potential problems were identified in aspects of comprehensibility, relevance, and comprehensiveness. These present opportunities for future research and refinement to ultimately improve the content validity of these measures for assessing child and adolescent health.