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Blood Test Tracker

Anti-CCP (Cyclic Citrullinated Peptide) Antibody

Measures antibodies against citrullinated proteins. A positive result is closely linked to rheumatoid arthritis and can appear years before joint symptoms.

AI-verified against cited sources. Awaiting expert reviewAlso called CCP, anti-CCP, ACPALOINC 33935-8

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What it is

Citrulline is a change that proteins can undergo in the body, especially during inflammation. In some people the immune system treats these changed proteins as foreign and makes anti-CCP antibodies, also called ACPA. This blood test measures them. It is usually ordered together with rheumatoid factor when someone has joint pain, swelling or stiffness. Most labs report a number in units and label the result negative, weak positive, moderate positive or strong positive.

Why it matters

Anti-CCP is one of the most useful blood tests for rheumatoid arthritis (RA). Across many studies, about 67 in 100 people with RA were positive, and about 95 in 100 people without RA were negative. A positive result together with joint symptoms makes RA more likely, and higher levels carry more weight in the criteria used to classify RA. It can also be positive before any symptoms: in one Swedish study, about a third of people who later developed RA already had it in blood given a median of 2.5 years earlier. A negative result does not rule RA out.

If it’s high

A higher number means more antibody. Positive results are strongly linked to rheumatoid arthritis, and a weak positive is less specific than a strong one. Positive results also occur in some other conditions and, rarely, in people who have none of them. Your clinician reads the result with your joint symptoms, an exam, rheumatoid factor and inflammation tests.

Common causes

  • Rheumatoid arthritis, including early disease before it is clearly visible
  • The period before RA symptoms start, since anti-CCP can show up years earlier
  • Other autoimmune conditions such as Sjögren's syndrome or lupus
  • Active tuberculosis or chronic lung disease
  • No known disease: Quest reports that about 2 in 100 random blood donors and people with other diseases test positive

What can help

  • Ask how this result fits with your joint symptoms, rheumatoid factor and inflammation tests
  • Ask whether you should see a rheumatologist
  • If your result is a weak positive, ask whether it should be repeated

Usual ranges

What labs print as the reference range, by who was tested. Ranges differ a little between labs, so the range on your own report is the one your result is judged against.

For adults: 0–19.9 U/mL. Source: Mayo Clinic Laboratories, Quest Diagnostics, ARUP Laboratories.

Mayo, Quest and ARUP result categories (assay-specific)

  • Negativebelow 20 U/mL
  • Weak positive20 to under 40 U/mL
  • Moderate positive40 to under 60 U/mL
  • Strong positive60 and above U/mL

What can affect your result

  • Test method: units and cutoffs differ between manufacturers, so results are not interchangeable
  • IgG-only versus IgG plus IgA tests: adding IgA finds some people who are IgG-negative (ARUP)
  • Stage of disease: anti-CCP can be positive before symptoms start
  • Other conditions, such as Sjögren's syndrome, lupus, tuberculosis or chronic lung disease
  • Results from different assays are not interchangeable. The same sample can land in different categories on different assays, because cutoffs and units differ and no common international standard exists.
  • Quest does not accept plasma, and samples that are grossly hemolyzed or lipemic may be rejected. ARUP also rejects contaminated, heat-inactivated and grossly icteric samples.
  • Some medicines, vitamins and supplements can affect lab results, so tell your clinician what you take (MedlinePlus), and follow the instructions you were given for the blood draw.

Anti-CCP can be positive years before joint symptoms start.

When to talk to a clinician

A positive result is not an emergency. Talk with a clinician soon if you have joint pain, swelling or stiffness, especially in the morning, that does not settle, or if you have fatigue or a low fever along with it. If a clinician has told you the result is a weak positive, ask whether and when it should be repeated.

Questions you could ask

  • Which test and cutoff did my lab use, so I can compare future results?
  • What other tests, such as rheumatoid factor, inflammation markers or joint imaging, would help?
  • How does this result fit with my joint symptoms and my other blood tests?
  • Should I see a rheumatologist?
  • If my result is a weak positive, should we repeat it?

Questions people ask

Does a positive anti-CCP mean I have rheumatoid arthritis?

Not by itself. Anti-CCP is a strong clue, and it is more specific than rheumatoid factor. But it is read together with joint symptoms, an exam, other blood tests and sometimes imaging. A weak positive is less specific than a strong positive, and a few people without RA test positive.

Can I have rheumatoid arthritis with a negative anti-CCP?

Yes. Across many studies, about 1 in 3 people with RA tested negative. Your clinician may use rheumatoid factor, inflammation tests, an exam and imaging as well.

Why do the units and cutoffs differ between labs?

There is no common international standard for anti-CCP tests, so each manufacturer sets its own scale and cutoff. Mayo, Quest and ARUP all use 20 units as the start of the positive range. Other tests use different numbers, so use the cutoff and flag on your own report.

Show the science and sources

For clinicians and researchers

Anti-CCP assays are immunoassays (ELISA or automated platforms) using second- or third-generation synthetic cyclic citrullinated peptides. Pooled sensitivity and specificity were 67% (95% CI 62 to 72) and 95% (94 to 97) in a meta-analysis of 37 studies, with a positive likelihood ratio of 12.46 and a negative likelihood ratio of 0.36, versus 69% and 85% for IgM rheumatoid factor (Nishimura 2007). Quest states that about 70% of people with RA are positive and about 2% of random blood donors and disease controls (Quest 11173). ARUP's IgG/IgA assay finds antibodies in about 66 to 74% of people with RA with a specificity of 96 to 99%. Six ACPA assays compared in one study had a sensitivity of 69.6 to 77.5% and a specificity of 87.8 to 96.4%, and for 12 commercial methods the ratio of the manufacturer cutoff to the IUIS/ASC ACPA standard varied between 5.6 and 28.5 (Rönnelid 2021). The 2010 ACR/EULAR RA classification criteria score serology as negative (0 points), low positive (2 points, above the lab's upper limit of normal up to about 3 times that limit) or high positive (3 points, above about 3 times that limit), so the same sample can score differently on different assays (Aletaha 2010, Rönnelid 2021). Mayo, Quest and ARUP all label below 20 units as negative, 20 to 39 as weak positive, 40 to 59 as positive (Quest and ARUP: moderate positive) and 60 or more as strong positive. Mayo uses an ELISA on IgG, Quest an IgG immunoassay and ARUP a semi-quantitative IgG/IgA ELISA. Anti-CCP positivity predated RA by years in a nested case-control study of blood donors (Rantapää-Dahlqvist 2003) and was associated with greater radiographic progression than IgM rheumatoid factor in three of four studies (Nishimura 2007).

LOINC 33935-8 (primary), 57093-7, 94874-5, 53027-9. Specimen: serum.

Sources

  1. Rheumatoid Arthritis Panel, Serum (test RAPAN, including CCP), Mayo Clinic Laboratories
  2. Cyclic Citrullinated Peptide (CCP) Antibody (IgG) (test code 11173), Quest Diagnostics
  3. Cyclic Citrullinated Peptide Antibody, IgG and IgA (test 3016632), ARUP Laboratories
  4. Meta-analysis: diagnostic accuracy of anti-cyclic citrullinated peptide antibody and rheumatoid factor for rheumatoid arthritis, Annals of Internal Medicine (2007)
  5. Antibodies against cyclic citrullinated peptide and IgA rheumatoid factor predict the development of rheumatoid arthritis, Arthritis & Rheumatism (2003)
  6. 2010 Rheumatoid arthritis classification criteria: an American College of Rheumatology/European League Against Rheumatism collaborative initiative, Arthritis & Rheumatism (2010)
  7. Autoantibodies in Rheumatoid Arthritis - Laboratory and Clinical Perspectives, Frontiers in Immunology (2021)
  8. CCP Antibody Test, MedlinePlus, National Library of Medicine
  9. LOINC codes verified with the NLM Clinical Tables LOINC search (e.g. 33935-8), U.S. National Library of Medicine

AI-verified against cited sources. Awaiting expert review. Last reviewed 2026-10-03. How we build and check these pages.

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