Associations Between Scores from Various WHOQOL- 1 BREF Taiwan Version Domains and EQ-5D-5L Utility Score in Rheumatology Outpatients

Background The World Health Organization Quality of Life-BREF (WHOQOL-BREF) and the EuroQol five-dimensional questionnaire (EQ-5D-5L) are widely used patient-reported outcome measures for assessing health-related quality of life. Although the EQ-5D-5L provides preference-based utility for health economic evaluation, the WHOQOL-BREF captures broader multidimensional aspects of quality of life. Evidence regarding their convergent validity in patients with rheumatic diseases remains limited. This study evaluated the associations between the WHOQOL-BREF Taiwan version and EQ-5D-5L utility among rheumatology outpatients. Methods In this cross-sectional study, rheumatology outpatients at a tertiary medical center in Taiwan completed the WHOQOL-BREF Taiwan version and EQ-5D-5L questionnaires. Associations between WHOQOL-BREF domains and EQ-5D-5L utility were evaluated using Spearman's rank correlation and multivariable linear regression analyses adjusted for age, sex, fracture history, stroke, interstitial lung disease, and disease category. Results A total of 141 participants were included (mean age, 55.5 ± 14.5 years; 61.0% female). All WHOQOL-BREF domains were significantly associated with EQ-5D-5L utility (all P<0.001), with the physical health domain demonstrating the strongest correlation. In separate multivariable models, all four domains remained independently associated with higher EQ-5D-5L utility after adjustment. In an exploratory model including all domains simultaneously, only the physical health domain remained significant, reflecting substantial shared variance rather than excessive multicollinearity. Conclusions The WHOQOL-BREF Taiwan version demonstrated good convergent validity with EQ- 5D-5L utility in rheumatology outpatients. While the physical health domain showed the strongest association with preference-based health utility, the remaining domains provided complementary information beyond physical functioning, supporting the complementary use of both instruments in rheumatology research and clinical practice.