Validity and reliability of EQ-5D-5L among patients with axial spondyloarthritis in Singapore

Abstract

Objective: This study aims to evaluate the reliability and validity of EuroQOL-5 Dimensions-5 Levels(EQ-5D-5L) among patients with axial spondyloarthritis (SpA) in Singapore.Methods: A cross-sectional study was conducted involving patients with axial SpA in an Asian ter-tiary hospital from 2017 to 2018. This study followed the COnsensus-based Standards for selectionof health Measurement Instruments framework. Construct validity was evaluated by testing 22 apriori hypotheses with other patient-reported outcomes measures. Cronbach's alpha was usedto estimate the internal consistency of the EQ-5D-5L, while its test-retest reliability was assessedusing weighted kappa and the intraclass correlation coefficient (ICC). The measurement error wasassessed by analyzing minimal detectable change (MDC).Results: The median age of included patients (n=118) was 35 years (interquartile range: 28, 49).Ninety-six (81.4%) patients were male, while 112 (94.9%) patients were of Chinese ethnicity. TheEQ-5D-5L demonstrated good internal consistency with a Cronbach’s alpha of 0.79. The test-retestreliability of the EQ-5D-5L was good with a weighted kappa of ≥0.61 for mobility, self-care, usualactivities, and anxiety/depression; the ICC was 0.92 and 0.99 for the EQ-5D-5L index and visualanalog scale (VAS) scores, respectively. The weighted kappa for the EQ-5D-5L pain/discomfort wasmoderate [0.53, 95% confidence interval: 0.41-0.60]. The MDC for EQ-5D-5L index and VAS scoreswas 0.06 and 4.5, respectively. Convergent validity was supported as all hypotheses were confirmedin the results.Conclusion: This study supports EQ-5D-5L as a valid and reliable instrument for assessing health-re-lated quality of life among patients with axial SpA in Singapore.