Residual disease activity in psoriatic arthritis: discordance between the rheumatologist's opinion and minimal disease activity measurement.

Objective: To assess how many PsA patients with an acceptable disease state according to the treating rheumatologist have quiescent disease defined as minimal disease activity (MDA).

Methods: This cross-sectional study included 250 PsA patients. To assess current clinical practice as closely as possible, acceptable disease state was not determined by predefined activity measures, but instead was defined by asking rheumatologists to refer those patients whom they considered sufficiently treated. Patients were evaluated for current disease activity including clinical assessments and patient reported outcomes (PROs).

Results: One-third (88/250) of the patients with acceptable disease state according to the rheumatologist did not fulfil MDA (MDA-). The presence of tender joints and patient pain and global disease activity scores most frequently contributed to not fulfilling MDA (not achieved in 83, 82 and 80%, respectively). However, also objective signs of disease activity were higher in the MDA- than MDA+ patient group: a swollen joint count >1 occurred in 35% vs 7% (P < 0.001), enthesitis >1 in 14% vs 3% (P = 0.002) and Psoriasis Area and Severity Index >1 in 43% vs 26% (P = 0.002). Residual disease was more frequent in females, elder patients and those with a raised BMI, independent of the treatment schedule, and negatively influenced PROs of function and quality of life.

Conclusion: One-third of the PsA patients with acceptable disease state according to the treating rheumatologist did not fulfil the MDA criteria and had residual disease activity on both subjective and objective disease activity measurements. As residual disease activity was associated with worse PROs, future strategy trials should evaluate if treatment adjustments are beneficial for this patient group.