Rheumatoid arthritis (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. There are a variety of treatments available to minimize the complications of RA, but they depend on making an accurate diagnosis and on beginning treatment before the development of significant joint damage. Rheumatoid factor (RF) has been the primary blood test used to detect RA and distinguish it from other types of arthritis and other inflammatory processes. However, the sensitivity and specificity of RF are not ideal; it can be negative in patients who have clinical signs of RA and positive in patients who do not.

CCP can be useful in diagnosing early RA. An elevated CCP can be found in a significant number of patients who have a negative RF, the classic test for RA, and therefore can help to make a diagnosis. According to the American College of Rheumatology, CCP antibodies may be detected in about 50-60% of patients with early RA (as early as 3-6 months after the beginning of symptoms). Early detection and diagnosis of RA allows doctors to begin aggressive treatment of the condition, minimizing the associated complications and tissue damage.

CCP may also be ordered to help evaluate the likely development of RA in patients with undifferentiated arthritis (those whose symptoms suggest but do not yet meet the criteria of RA). The reason it is useful in confounding clinical presentations is that CCP is a more specific test for RA then the traditional RF. According to American College of Rheumatology, approximately 95% of patients with a positive CCP will develop RA in the future.

CCP is primarily ordered along with an RF test when a patient has previously undiagnosed inflammatory arthritis or has been diagnosed with undifferentiated arthritis. It may be ordered as a follow-up test to a negative RF test when clinical signs, such as symmetrical joint pain and inflammation, lead the doctor to suspect RA.

As a rule, test results outside the context of clinical symptoms and signs cannot be judged. Nonetheless, if a patient is positive for both CCP and RF, it is very likely that they have RA and it is likely that they may develop a more severe form of the disease. If a patient is positive for CCP but not RF and clinical signs suggest RA, then it is likely that they have early RA or that they will develop RA in the future.

If a patient is negative for CCP but has a positive RF, then the clinical symptoms and signs are more vital in determining whether a patient has RA versus some other inflammatory condition. If a patient is negative for both CCP and RF, then it is less likely that they have RA. It must be emphasized, however, that RA is a clinical diagnosis and may be made in the absence of positive autoantibodies.

The CCP test is promising but not yet widely used. Its ultimate clinical usefulness and the ways in which it will be used have yet to be determined.