Measurement of Minimal Disease Activity in Psoriatic Arthritis Using the Patient-Reported Outcomes Measurement Information System–Physical Function or the Health Assessment Questionnaire Disability Index

Objective: 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). Methods: Comprehensive PsA disease activity was collected concomitantly with the HAQ DI and the PROMIS-PF measures in a PsA cohort. The PROMIS-PF–based MDA definitions were built using the existing cross-walk between the scores: HAQ DI ≤0.5 equivalent to a PROMIS-PF T score of ≥41.3. We assessed agreement between MDA (MDA HAQ DI) and the PROMIS-PF MDA definitions (MDA PROMIS-PF short form 4a and MDA PROMIS-PF bank) at each visit and longitudinally (MDA state changes between consecutive visits) through the kappa statistic. The predictive value of the MDA PROMIS-PF for the MDA HAQ DI was assessed using receiver operator characteristic (ROC) curve analysis. Results: A total of 100 participants contributed 352 observations with up to 5 visits. The mean ± SD age was 52 ± 12 years, 60% were female, and 43% were in MDA at baseline. The kappa statistic for the PROMIS-PF–based MDA reflected excellent agreement with the HAQ DI MDA: κ = 0.94 (95% confidence interval [95% CI] 0.90–0.97) for MDA PROMIS-PF bank, and κ = 0.90 (95% CI 0.80–0.95) for MDA PROMIS-PF4a. Higher longitudinal agreement was seen between the MDA HAQ DI and the MDA PROMIS-PF bank versus the MDA PROMIS-PF4a between consecutive visits: κ values ranged between 0.81 and 0.94 versus a range between 0.72 and 0.84, respectively. The area under the ROC curve for predicting the MDA HAQ DI was 0.97 for the MDA PROMIS-PF bank and 0.95 for the MDA PROMIS-PF4a. Conclusion: Excellent agreement was seen between the HAQ DI and the PROMIS-based MDA definitions both cross-sectionally and longitudinally. The PROMIS-PF bank and PROMIS-PF4a are accurate replacements for the HAQ DI in calculating MDA state in PsA.