What does a positive anti-cyclic citrullinated peptide (anti-CCP) test mean?

From the Guidelines

A positive anti-cyclic citrullinated peptide (anti-CCP) test is a strong indicator of rheumatoid arthritis (RA), with high specificity and a positive likelihood ratio of 15.39, as reported in the most recent study 1. This test detects antibodies that target citrullinated proteins, which are modified proteins found in the body. The presence of anti-CCP antibodies is highly specific for RA, meaning they rarely appear in people without the disease, making this test more specific than the rheumatoid factor test. Some key points to consider include:

• A positive result often appears early in the disease process, sometimes even before symptoms develop, allowing for earlier diagnosis and treatment.
• The test is particularly valuable because higher levels of these antibodies may indicate more aggressive disease that could require more intensive treatment.
• However, not all RA patients test positive, with a sensitivity of about 66% as reported in 1, so a negative result doesn't rule out RA if other symptoms and signs are present.
• The test results should always be interpreted alongside clinical symptoms, physical examination findings, and other laboratory tests by a rheumatologist to establish a definitive diagnosis and appropriate treatment plan. It's also important to note that the management of early arthritis, including the use of anti-CCP testing, has been addressed in various guidelines, such as those from the European Standing Committee for International Clinical Studies Including Therapeutics (ESCISIT) 1 and the American College of Rheumatology 1, which emphasize the importance of early diagnosis and treatment to prevent further joint damage and disability. Additionally, the 3E Initiative provides recommendations on how to investigate and follow-up undifferentiated peripheral inflammatory arthritis, including the use of anti-CCP testing 1.

From the Research

What is a Positive Anti-CCP Test?

A positive anti-cyclic citrullinated peptide (anti-CCP) test means that the patient has antibodies against cyclic citrullinated peptides in their blood.

• This test is used to diagnose rheumatoid arthritis (RA), a common autoimmune disease that affects the joints 2, 3, 4.
• The anti-CCP test is more specific than the rheumatoid factor (RF) test, with a specificity of 95% compared to less than 90% for RF 4.
• The test has a comparable sensitivity to RF, with more than 70% of patients with RA testing positive for anti-CCP antibodies 4.

Diagnostic Value of Anti-CCP Test

The anti-CCP test is widely accepted as an indispensable tool for diagnosis and early treatment in the management of rheumatoid arthritis patients.

• A study found that the anti-CCP test had a sensitivity of 47.2% and a specificity of 92.9% for diagnosing RA in Iranian patients 5.
• Another study found that the test had a sensitivity of 76% and a specificity of 100% for diagnosing RA, with an overall diagnostic accuracy of 83.2% 6.
• The test can also be used to predict the development of erosive RA and to identify patients who are likely to have severe disease and irreversible damage 3, 4.

Clinical Implications

A positive anti-CCP test can have significant clinical implications for patients with RA.

• It can help diagnose RA early, which is critical for initiating effective treatment and preventing irreversible damage 3, 4.
• It can also help identify patients who are at risk of developing severe disease and irreversible damage, allowing for more aggressive treatment 3.
• The test can be used in combination with other tests, such as RF, to increase its diagnostic value 5.