Measuring disease activity in psoriatic arthritis: PASDAS implementation in a tightly monitored cohort reveals residual disease burden.

OBJECTIVES: We aimed to investigate the disease activity and overall disease burden of (subgroups of) patients with PsA using the Psoriatic Arthritis Disease Activity Score (PASDAS) in an already tightly monitored cohort. METHODS: This is a cross-sectional study evaluating data from the first visit of 855 PsA patients after implementation of the PASDAS in our tightly monitored cohort [e.g. DAS 28 (DAS28) was provided as an anchor]. Differences in clinical outcomes between subgroups of patients using established cut-offs for disease activity status [i.e. very low (VLDA), low (LDA), moderate (MDA), and high disease activity (HDA)] were examined. RESULTS: Based on the PASDAS, 53.1% of patients were in VLDA/LDA. 29.5% of patients had ≥1 swollen joint, 20.6% had ≥1 enthesitis index point and 3.0% had active dactylitis. Based on DAS28, 77.5% of the patients were in VLDA/LDA. Patients reaching both DAS28 VLDA/LDA status and PASDAS VLDA/LDA status [N = 445 (52.0%)] were compared with patients reaching only DAS28 VLDA/LDA status [N = 218 (25.5%)]. For these latter patients, significantly worse scores on separate parameters were found in measures used for PASDAS/DAS28 calculation (e.g. swollen and tender joint count and patient's visual analogue scale global disease activity) as well as other disease measures (e.g. function and inflammatory back pain). This result remained, even when the stricter VLDA cut-off was used for the DAS28. CONCLUSION: PASDAS implementation uncovered relevant residual disease activity in a quarter of patients previously assessed as being in DAS28 VLDA/LDA, underscoring the potential value of PASDAS measurements in PsA clinical care.