The Anti-Cyclic Citrullinated Peptide (anti-CCP) test is a highly specific blood test that helps in the diagnosis of rheumatoid arthritis (RA), a chronic autoimmune disease where the immune system attacks the joints. The test detects the presence of anti-CCP antibodies, which are abnormal antibodies produced by the body that target citrullinated peptides in the joints. Citrullination is a natural process in the body, but in some individuals, it can trigger the immune system to mistakenly attack the joints, leading to inflammation, pain, and irreversible damage.

The presence of anti-CCP antibodies is a strong indicator of rheumatoid arthritis, often preceding clinical symptoms by years. It is one of the most specific markers for diagnosing RA, particularly in patients who exhibit symptoms like joint pain, swelling, and stiffness. High levels of anti-CCP antibodies may indicate a higher risk of developing a severe form of rheumatoid arthritis, with more aggressive joint damage.