Remission criteria and activity indices in psoriatic arthritis

Remission criteria and activity indices used in rheumatoid arthritis (RA) are often applied in psoriatic arthritis (PsA). Some new indices have been specifically developed for PsA. Our objective was to evaluate the performance of different remission criteria and activity indices in PsA. This is a cross-sectional study that includes consecutive patients with PsA. Information necessary to complete the following indices was captured: Composite Psoriatic Disease Activity Index (CPDAI), Psoriatic Arthritis Screening and Evaluation (PASE), Disease Activity Index for Psoriatic Arthritis (DAPSA), Disease Activity Score in 28 Joints (DAS28), Simplified Disease Activity Index (SDAI), Clinical Disease Activity Index (CDAI), and American College of Rheumatology and European League Against Rheumatism (ACR/EULAR) Boolean RA remission criteria. Patients were classified according to activity categories (remission, low, medium, or high disease activity). Correlation between indices was established. Fifty-five patients were included. Mean age was 53 years (SD = 12), and 35 (63.6 %) were males. Mean PsA disease duration was 5.9 years (SD = 8.5), and mean psoriasis duration was 15.9 (SD = 12.6). We found important differences in the percentage of patients classified as in remission by applying different remission criteria: DAS28 = 33 % (95 % confidence interval (CI) 20-45) vs ACR/EULAR = 4 % (95 % CI 1-17). Particularly, DAS28 and minimal disease activity seemed to be less stringent in PsA than the other indices. Of the specific PsA indices evaluated, CPDAI showed the poorest correlation with all the other activity measurements, although differences were not statistically significant in most cases. Disease activity in PsA is measured by many different indices. In spite they all showed good correlations between them, they classified different patients in different disease status.