Reliability and validity of the EQ-5D-3L for Kashin–Beck disease in China

Background Kashin–Beck Disease (KBD) is an endemic osteoarthropathy in areas which extend from the North-East to the South-West of China. Most of the patients with KBD suffer multiple dysfunctions in major joints causing decreased health status. However because of their low education level and unique living habits, it is hard to find tools to measure the health-related quality of life (HRQOL). European quality of life (EQ-5D-3L) patient-reported instrument is widely used to measure HRQOL. This study aimed to establish the validity and reliability of the Chinese version of the EQ-5D-3L for evaluating HRQOL of KBD individuals in rural area. Methods 368 individuals who were suffering from KBD were recruited through stratified multistage random sampling from Shaanxi province, China. The EQ-5D-3L and the WHOQOL-BREF were administrated in each individual by face to face interview. Test–retest reliability was assessed at 10–14 days intervals. The test–retest reliability was measured by calculating the Kappa coefficients for EQ-5D-3L five dimensions. For the EQ VAS, the intraclass correlation coefficient (ICC) was computed. Convergent and divergent analysis, construct validity was established using Spearman’s rank correlation between the EQ-5D-3L and the WHOQOL-BREF. Known groups’ validity was examined by comparing groups with a priori expected differences in health-related quality of life (HRQOL). Results For 362 individuals (98%), comprehensive data of all the EQ-5D-3L dimensions were available. Kappa values of the EQ-5D-3L five items ranged from 0.324 to 0.554. ICC of the EQ VAS was 0.497. For convergent validity, the three items (self-care, usual activity, and mobility) of EQ-5D-3L, index scores, and VAS showed moderate correlations with the physical health domain of the WHOQOL-BREF (r absolute value ranged from 0.339 to 0.475). For divergent validity, the 5 items of EQ-5D-3L showed weak or no correlations with environment and social relationship domains of WHOQOL-BREF. The Chinese EQ-5D-3L clearly demarcated between groups which were reporting severe disease degree, poorer general health, more number of painful joints with worse HRQOL. Conclusions The EQ-5D-3L Chinese Version demonstrated fair to moderate levels of test–retest reliability and adequate construct validity in KBD individuals in China.