Developing and testing culturally relevant bolt-on items for EQ-5D-5L in Chinese populations: a mixed-methods study protocol

Introduction EQ-5D is one of the most frequently used health-related quality of life (HRQoL) measures but has been found to be insensitive in detecting differences in health status in some general populations and disease groups. For example, the appropriateness of applying EQ-5D in the Chinese cultural setting has been widely discussed. Adding additional HRQoL dimensions (bolt-on items) can be a solution to both retain the original descriptive system of EQ-5D, while enhancing its sensitivity to the local context. To date, no studies have proposed culturally relevant bolt-ons for China or examined the psychometric properties of such bolt-on items. This protocol documents the identification, development, selection and psychometric testing of culturally relevant bolt-on items for EQ-5D-5L in China.Methods and analysis We will identify and develop candidate bolt-on items that are most relevant in the Chinese culture, through former literature reviews on health concepts important for the Chinese population, conducting expert consultations and qualitative interviews. We will quantitatively test the acceptability and measurement properties (including distributional characteristics and construct validity) of the candidate items in both general and disease populations in a cross-sectional setting. The patient group will be followed up to collect two-time-point data to assess test-retest reliability of the candidate items. Bolt-on item selection will consider both the qualitative and quantitative evidence gathered. This protocol outlines a comprehensive mixed-methods process for identifying, developing, selecting and testing bolt-on items that are relevant and culturally appropriate in China. This study may serve as a guide for similar initiatives in other cultural contexts.Ethics and dissemination This study received ethics approval from the Institutional Review Board of School of Public Health, Fudan University (IRB number: 2022-TYSQ-03-154). Study findings will be disseminated through international peer-reviewed journal articles as well as public, academic presentations at national and international conferences.