Test-retest reliability for HAQ-DI and SF-36 PF for the measurement of physical function in psoriatic arthritis

Objective. Due to no existing data, we aimed to derive evidence to support test-retest reliability for the Health Assessment Questionnaire–Disability Index (HAQ-DI) and 36-item Short Form Health Survey physical functioning domain (SF-36 PF) in psoriatic arthritis (PsA). Methods. We identified datasets that collected relevant data for test-retest reliability for HAQ-DI and SF-36 PF, and evaluated them using Outcome Measures in Rheumatology (OMERACT) Filter 2.1 methodology. We calculated intraclass correlation coefficients (ICC) as a measure of test-retest reliability. We then conducted a quality assessment and evaluated the adequacy of test-retest reliability performance. Results. Two datasets were identified for HAQ-DI and 1 for SF-36 PF in PsA. The quality of the datasets was good. The ICCs for HAQ-DI were good and excellent in study 1 (0.90, 95% CI 0.79–0.95) and study 2 (0.94, 95% CI 0.89–0.97). The ICC for SF-36 PF was excellent (0.96, 95% CI 0.92–0.98). The performance of test-retest reliability for both instruments was judged to be adequate. Conclusion. The new data derived support good and reasonable test-retest reliability for HAQ-DI and SF-36 PF in PsA.