Background: Cyclic-Citrullinated Peptide Antibody Test
The cyclic-citrullinated peptide (CCP) antibody test detects the presence of autoantibodies to citrullinated peptides in serum. Abnormal citrullination of various peptides is present in a variety of human diseases, including rheumatoid arthritis, psoriasis, and multiple sclerosis. However, the formation of antibodies to citrullinated peptides seems to be specific for adult patients with rheumatoid arthritis. The second-generation anti-CCP2 assay is currently the most widely used anti-CCP assay. Anti-CCP antibodies and anti-citrullinated filaggrin antibodies are locally produced in inflamed joints, and citrullinated fibrin is found in the synovia of patients with rheumatoid arthritis. In adults, a CCP test is usually ordered along with a rheumatoid factor test when evaluating a patient with inflammatory arthritis and when rheumatoid arthritis is considered in the differential diagnosis. The prevalence and utility of a positive CCP test result in children with juvenile idiopathic arthritis or with associated rheumatic conditions is not clear.