To assess the interchangeability of the Health Assessment Questionnaire-Disability Index (HAQ-DI) with the Patient-Reported Outcomes Measurement Information System-Physical Function (PROMIS-PF) in the calculation of minimal disease activity (MDA) in psoriatic arthritis (PsA).
Comprehensive PsA disease activity was collected concomitantly with HAQ-DI and PROMIS-PF measures in a PsA cohort. PROMIS-based MDA definitions were built using the existing cross-walk between the scores: HAQ-DI≤0.5 equivalent to a PROMIS-PF Tscore≥41.3. We assessed agreement between MDA (MDA HAQ-DI) and PROMIS-PF MDA definitions (MDA PROMIS-PF4a, MDA PROMIS-PF Bank) at each visit and longitudinally (MDA state changes between consecutive visits) through the kappa statistic. The predictive value of MDA PROMIS-PF for MDA HAQ-DI was assessed using ROC curve analysis.
One hundred participants contributed 352 observations with up to five visits. Mean (SD) age was 52 (12) years, 60% were female, and 43% were in MDA at baseline. Kappa statistic for PROMIS-PF based MDA reflected excellent agreement with HAQ-DI MDA: kappa=0.94 (95% CI 0.90-0.97) for MDA PROMIS-PF Bank, and kappa=0.90 (95% CI 0.80-0.95) for MDAPROMIS-PF4a. Higher longitudinal agreement was seen between MDA HAQ-DI and MDA PROMIS-PF Bank versus MDA PROMIS-PF4a between consecutive visits: kappa ranged between 0.81-0.94 versus 0.72-0.84, respectively. Area under ROC curve for predicting MDA HAQ-DI was 0.97 for MDA PROMIS-PF Bank and 0.95 for MDA PROMIS-PF4a.
Excellent agreement was seen between HAQ-DI and PROMIS-based MDA definitions statically and longitudinally. The PROMIS-PF Bank and PROMIS-PF4a are accurate replacements for the HAQ-DI in calculating MDA state in PsA.

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