The anti-CCP antibody test measures your body’s level of antibodies that commonly target specific proteins found in the joints. These antibodies are commonly found in rheumatoid arthritis patients. Let’s look at how doctors use this test as an auto-immune marker.
What Are Anti-cyclic Citrullinated Peptide Antibodies and why are they elevated in RA?
Anti-cyclic citrullinated peptide (anti-CCP) antibodies are commonly found in patients with rheumatoid arthritis (RA), an autoimmune disorder that destroys the joints throughout the body . These antibodies are made as a direct attack of specific proteins found naturally in the body.
Anti-CCP antibodies target proteins in which the amino acid arginine has been converted (citrullinated) into another amino acid called citrulline. Citrullinated proteins increase their levels substantially when an inflammatory cascade is activated such as in RA [1, 2].
Normally, the immune system is tolerant of these proteins, but in patients with RA, the body mounts an immune response and creates antibodies to target and destroy these citrullinated proteins .
This immune activation destroys healthy tissue in the joints and worsens RA symptoms .
Anti-CCP antibodies may also be detected in other inflammatory diseases and conditions involving the joints and connective tissue, including [4, 5, 6, 7]:
- Psoriatic arthritis, a form of arthritis that occurs in people with the skin disease psoriasis
- Sjogren’s syndrome
- Systemic lupus erythematosus
- Hepatitis C infection
Anti-CCP antibodies belong to a family of similar antibodies known as anti-citrullinated protein antibodies (ACPAs) .
Some tests can detect the presence of other types of ACPAs that the anti-CCP antibody test can’t detect. However, the anti-CCP antibody test is the most widely-used ACPA test in clinical practice due to its accuracy .
The anti-CCP antibody test may also be referred to as an ACPA antibody test.
How is the Test Used?
Anti-CCP antibodies can be detected in the early stages of RA, even before symptoms are present. They are more often found in severe forms of the disease and increase the risk of more rapid destruction of the joints [3, 8, 4].
Until recently, rheumatoid factor (another antibody involved in RA) was the only antibody used to help diagnose the disease. However, in 2010, the American College of Rheumatology changed their criteria for diagnosing RA to include the presence of anti-CCP antibodies .
Testing for anti-CCP antibodies helps doctors to diagnose RA patients and determine how severe the disease is, as well as predict the likely outcome of the disease. Early detection of anti-CCP antibodies is crucial to properly treat the disease and stop its progression .
Anti-CCP antibody testing is not used to monitor RA because changes in antibody levels are not linked to changes in disease activity and patients tend to remain positive even with the reduction or disappearance of the symptoms of RA [11, 12, 13].
The test is also not used to screen for RA patients because it can frequently miss individuals who have the disease .
Anti-CCP Antibody Testing
Anti-CCP antibody testing usually requires that you have your blood drawn and sent to a lab.
The test is ordered when a person displays signs and/or symptoms of rheumatoid arthritis. These include :
- Painful or swollen joints (especially the fingers and wrists), usually occurring on both sides of the body
- Stiffness in the joints that gradually decreases throughout the day
- Muscle weakness and fatigue
- Rheumatoid nodules, small hard lumps that develop under the skin
A rheumatoid factor (RF) test is commonly ordered alongside an anti-CCP test to help make a diagnosis. Your doctor will also order ESR and CRP tests that measure inflammation.
Anti-CCP antibodies are the most specific test for diagnosing RA [16, 17].
This means that false positives are rare and therefore a positive result means you are much more likely to have RA.
However, it isn’t a very sensitive marker, which means that a negative result does not necessarily rule out rheumatoid arthritis .
There is a newer version of the test that has improved sensitivity, which reduces the chance of a false negative. However, most labs do not offer this test yet [1, 18].
Anti-CCP antibodies can be detected in RA patients years before they show any symptoms [19, 20].
There are also tests that you can take at your doctor’s office which only require a blood sample from a finger prick. Fingerstick tests give you results within 10 minutes, allowing your doctor to give you immediate feedback .
These tests are slightly less accurate than tests that require blood draws that are then sent away to a lab for analysis. Currently, they are not widely used in clinical practice .
What Do Your Results Mean?
The normal level of anti-CCP antibodies is less than 20 units/mL. Anything over this level means that you test positive for the antibodies and anything below means you test negative .
About 70% of RA patients test positive for anti-CCP antibodies [4, 23].
A positive result by itself does not automatically lead to a diagnosis.
If you test positive for anti-CCP antibodies but not rheumatoid factor (RF) and are experiencing any symptoms of the disease, you may have RA.
Around 20% of RA patients who test negative for RF will test positive for anti-CCP antibodies .
If you also test positive for RF, you likely have the disease .
To make a conclusive diagnosis, your doctor will take into account both of your antibody results in combination with CRP and ESR tests and any symptoms you have .
Patients who test positive for anti-CCP antibodies at the time of diagnosis are likely to progress more rapidly and develop more destructive forms of RA [13, 26, 11].
If you test positive for anti-CCP antibodies, yet you’re healthy and aren’t showing symptoms of RA, you have a much greater risk of developing the disease .
Even if you test negative for both anti-CCP and RF antibodies this also doesn’t rule out RA when you are experiencing symptoms. Around 30% of RA patients test negative for both antibodies .
In these cases, your doctor will need to factor in the severity of your symptoms, CRP and ESR, and imaging tests .
Treating RA early on (within 6 after symptoms begin) is crucial in preventing the disease from progressing and reducing joint damage and disability .
If you test positive for anti-CCP and are diagnosed with RA, your doctor will likely pursue a more aggressive treatment regimen. This includes a combination of medications called disease-modifying antirheumatic drugs (DMARDs) that includes methotrexate (Trexall) and biologics (drugs made from living organisms) such as infliximab (Remicade) and etanercept (Enbrel) [29, 4].
In addition to improving symptoms and preventing and reducing joint damage, these medications can reduce anti-CCP levels substantially [30, 31, 4].
While RA is a lifelong disease, diagnosing it early and treating it properly will give the best chance at controlling its progression and allowing you to live a healthy and active lifestyle.
Anti-CCP antibodies are commonly found in rheumatoid arthritis patients and are thought to play a key role in the disease process. Doctors use the anti-CCP antibody test in combination with other tests and symptoms to diagnose rheumatoid arthritis and determine the likely course of the disease. Testing positive for anti-CCP antibodies increases the risk of developing a more aggressive form of rheumatoid arthritis. You might be able to help lower your inflammatory joint symptoms by maintaining adequate vitamin D levels, addressing any gum disease you may have, and quitting smoking.