Validation of minimal disease activity criteria for psoriatic arthritis using interventional trial data.

Objective: New criteria for minimal disease activity (MDA) in psoriatic arthritis (PsA) have been developed. The aim is to provide further validation of these criteria using data obtained in interventional trials with infliximab, a drug with proven efficacy in PsA.

Methods: The data were obtained from patients in phase II and III infliximab studies of PsA. In both studies, patients with active PsA were treated with infliximab (5 mg/kg) or placebo followed by a period of treatment with infliximab. Between-group comparisons in terms of those achieving MDA and the relationship of MDA to American College of Rheumatology outcomes, C-reactive protein levels, and radiologic progression were performed.

Results: In the Infliximab Multinational Psoriatic Arthritis Controlled Trial, 48% (15 of 31) of infliximab-treated patients achieved MDA at week 16, compared with 3% (1 of 32) taking placebo (P < 0.0001). At week 50, 96% of those patients who achieved MDA showed no progression of radiologic disease (increase in the modified Sharp/van der Heijde score of < or = 0), compared with 67% of those who did not achieve MDA (P = 0.012). In the Induction and Maintenance Psoriatic Arthritis Clinical Trial 2, 52% (40 of 77) of infliximab-treated patients achieved MDA at week 24, compared with 21% (17 of 80) receiving placebo (P < 0.001). At week 54, 78% of those patients who achieved MDA had no radiologic progression, compared with 57% of those who did not achieve MDA (P = 0.009).

Conclusion: Patients with active PsA achieving MDA with effective therapy have a significant reduction in radiographic progression. Aiming for low levels of disease activity can improve the outcome of patients with PsA even in a disease-modifying antirheumatic drug-resistant cohort. The new MDA criteria could provide an objective target for treatment in trials and clinical practice.