Cyclic citrullinated peptide antibodies are autoantibodies produced by the immune system that are directed against cyclic citrullinated peptides (CCP). This test detects and measures anti-CCP antibodies in the blood.

Citrulline is naturally produced in the body as part of the metabolism of the amino acid arginine. However, in joints with rheumatoid arthritis (RA), this conversion may occur at a higher rate. Citrulline changes the protein structure and can trigger an immune response, producing autoantibodies against joint proteins. The CCP antibody test helps to diagnose RA and can be useful in identifying people with a more rapidly erosive form of the disease.

RA is a chronic, systemic autoimmune disease that causes inflammation, pain, stiffness, and destructive changes in the hands, feet, and other joints throughout the body. It can affect anyone at any age, but it usually develops between the ages of 40 and 60, and about 75% of those affected are women. The course of RA and its prognosis are variable. It may develop and progress slowly or rapidly. It may go into remission in some people and, in a few, it may go away. Left untreated, RA can shorten a person's lifespan and can, within a few years, leave many of those affected too disabled to work.