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

Abstract

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. A cross-sectional study was conducted involving patients with axial SpA in an Asian tertiary hospital from 2017 to 2018. This study followed the COnsensus-based Standards for selection of health Measurement Instruments framework. Construct validity was evaluated by testing 22 a priori hypotheses with other patient-reported outcomes measures. Cronbach's alpha was used to estimate the internal consistency of the EQ-5D-5L, while its test-retest reliability was assessed using weighted kappa and the intraclass correlation coefficient (ICC). The measurement error was assessed by analyzing minimal detectable change (MDC). 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. The EQ-5D-5L demonstrated good internal consistency with a Cronbach's alpha of 0.79. The test-retest reliability of the EQ-5D-5L was good with a weighted kappa of ≥0.61 for mobility, self-care, usual activities, and anxiety/depression; the ICC was 0.92 and 0.99 for the EQ-5D-5L index and visual analog scale (VAS) scores, respectively. The weighted kappa for the EQ-5D-5L pain/discomfort was moderate [0.53, 95% confidence interval: 0.41-0.60]. The MDC for EQ-5D-5L index and VAS scores was 0.06 and 4.5, respectively. Convergent validity was supported as all hypotheses were confirmed in the results. This study supports EQ-5D-5L as a valid and reliable instrument for assessing health-related quality of life among patients with axial SpA in Singapore.