The CCP test (Cyclic Citrullinated Peptide Antibody) is a blood test used to detect anti-citrullinated peptide antibodies in the body. This test is primarily used for the diagnosis of rheumatoid arthritis in the early stages of the disease. CCP antibodies indicate an autoimmune response in which the immune system mistakenly attacks citrullinated proteins (a type of modified protein found in joint tissues). This test is more specific than the rheumatoid factor (RF) test and plays a key role in the early diagnosis and differentiation of rheumatoid arthritis from other inflammatory joint diseases. High levels of CCP antibodies are often associated with more severe disease progression and joint damage and help physicians predict the disease course and choose appropriate treatment. This test is usually used alongside other laboratory tests and clinical symptoms to confirm the diagnosis.