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 Medical Outcome Survey Short-Form-36 item 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 OMERACT Filter 2.1 methodology. We calculated intra-class 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 one for SF-36 PF in PsA. The quality of the datasets was good. The ICCs for HAQ-DI were excellent in both datasets: 0.94 (95% CI: 0.88 to 0.97) and 0.94 (95% CI: 0.89 to 0.97). The ICC of SF-36 PF was good (0.89, 95% CI: 0.76 to 0.95). 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.