Frequency, Predictors, and Prognosis of Sustained Minimal Disease Activity in an Observational Psoriatic Arthritis Cohort

Objective. To establish the frequency and predictors of minimal disease activity in psoriatic arthritis (PsA) and to investigate the prognostic ability of minimal disease activity criteria to predict future joint damage. Methods. The study was conducted using an observational PsA cohort. Patients were classified as being in minimal disease activity if they fulfilled the criteria on consecutive visits for >12 months. Predictive factors for minimal disease activity and joint damage were investigated using regression models. Joint damage progression was based on clinically damaged joint counts. Results. Of the 344 patients, 208 (60%) achieved minimal disease activity at >= 1 visit and 116 (34%) achieved minimal disease activity for > 12 months (sustained minimal disease activity). The average duration of minimal disease activity was 28 months (range 12-48 months). Twelve patients (10%) experienced a flare of disease after 34 months in minimal disease activity. Low erythrocyte sedimentation rate (ESR) and oligoarthritis were predictors of achieving sustained minimal disease activity (P < 0.03). The mean change in damaged joint counts was 0.931 (range 0-12) in the sustained minimal disease activity group and 2.245 (range 0-17) in the controls (P < 0.001). Of the sustained minimal disease activity group, 69% showed no progression of joint damage, compared with 51% in the control group. Elevated ESR, baseline joint damage, and use of biologic therapies increased the likelihood of damage progression (P < 0.05). Conclusion. Minimal disease activity was achieved by a significant proportion of patients and was sustained in one-third of the population studied. Patients achieving sustained minimal disease activity had a significant reduction in joint damage progression. Other factors, representing disease activity and disease severity, impact on the likelihood of achieving sustained minimal disease activity and on damage progression.