Antibodies against cyclic citrullinated peptide (CCP) in psoriatic patients with or without joint inflammation

Objective: To compare the prevalence of anti-CCP antibodies in psoriatic patients with and without joint inflammation, patients with early RA, and controls. Methods: Anti-CCP antibodies ( cut off level 5 U/ml) were measured in 160 patients with psoriatic arthritis (PsA), 146 patients with psoriasis but no arthritic disease, 101 patients with early RA, and 102 healthy controls by ELISA. Results: 11 (7%) patients with PsA, 75 (74%) patients with early RA, 2 (2%) healthy controls (2%), and 1 (0.7%) patient with psoriasis without arthritis had anti-CCP antibodies above the cut off level. The presence of anti-CCP antibodies was not related to radiological changes and/ or deformity and functional impairment in PsA. 8/ 11 patients with PsA and anti- CCP antibodies had a polyarthritic disease, and all fulfilled the ACR criteria for RA at 4 year follow up. Five of these 8 patients also had manifestations such as dactylitis, DIP involvement, radiological changes associated with PsA, and/ or enthesitis. In multiple logistic regression analysis with polyarthritis as the dependent variable, anti-CCP antibodies and rheumatoid factor significantly distinguished RA from PsA. Conclusions: Anti-CCP antibodies were more prevalent in patients with PsA than in patients with psoriasis without arthritis, but less prevalent than in patients with early RA. Patients with PsA positive for anti-CCP antibodies more often had polyarthritic disease, but the presence of anti-CCP antibodies did not relate to radiological changes and/ or deformity and functional impairment.