The relationship between peripheral arthritis and anti-cyclic citrullinated peptide antibodies in ankylosing spondylitis

Abstract

Objectives: Although ankylosing spondylitis (AS) primarily affects the axial skeleton, peripheral arthritis occurs in up to 35% of cases. Anti-cyclic citrullinated peptide (anti-CCP) antibodies are highly specific for rheumatoid arthritis, whereas their role in AS remains unclear. In this study we aimed to assess the prevalence of anti-CCP antibodies in AS patients with peripheral arthritis and their clinical association with peripheral arthritis. Methods: We retrospectively selected for this study 625 AS patients who fulfilled the modified New York criteria. The patients were divided into those with and those without peripheral arthritis on smoking history, the basis of symptoms, physical examination and medical records. The presence of anti-CCP antibodies was investigated in all the patients. Results: Anti-CCP antibodies were found in 4% (25/625) of the patients, and peripheral arthritis was diagnosed in 37.4% (234/625) of the patients. In multiple logistic regression, peripheral arthritis was significantly associated with female gender (P = 0.001) and the presence of anti-CCP antibodies (P = 0.001), especially with the presence of titers of anti-CCP antibodies over three times the normal upper limit of the laboratory and assay. Conclusions: Anti-CCP antibodies are occasionally present in AS, and their presence may be helpful as a serum marker for predicting peripheral arthritis.