Sensitivity of the classification of psoriatic arthritis criteria in early psoriatic arthritis.

Objective: To determine the sensitivity of the CASPAR criteria in patients with early psoriatic arthritis (PsA).
Methods: Consecutive patients with a clinical diagnosis of PsA and a disease duration < 12 months were enrolled for study. The proportion of patients meeting the criteria (i.e., the sensitivity) was determined.
Results: Forty-four patients with early PsA (23 women, 21 men; mean age 51 yrs, range 16-90) were enrolled. Mean disease duration (+/- SD) was 15.8 +/- 14.3 weeks (range 0.1-50.9 wks). Thirty-four patients satisfied the criteria at the first visit (sensitivity 77.3%). Most patients met the skin and laboratory criterion, i.e., they were rheumatoid factor-negative, while only 2 satisfied the radiologic criterion.
Conclusion: Our findings suggest a less satisfactory performance of the CASPAR criteria when applied in early PsA. Lower sensitivity could mainly depend on the small proportion of patients fulfilling the radiologic criterion.