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 > or = 1 visit and 116 (34%) achieved minimal disease activity for > or = 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.