Anti-CCP (ACPA)

The anti-CCP test measures antibodies to cyclic citrullinated peptides in the blood. It is performed for painful and swollen joints when a doctor suspects rheumatoid arthritis, and a positive result with typical symptoms strongly supports this disease. It is most often measured together with rheumatoid factor (RF).

Who the test is for

• people with painful and swollen joints, particularly the small joints of the hands and feet on both sides of the body;
• people whose joints are stiff for more than half an hour in the morning;
• people whose joint symptoms last several weeks or recur;
• people with a negative rheumatoid factor in whom rheumatoid arthritis remains suspected, and people with a positive rheumatoid factor without a clear reason;
• people with undifferentiated arthritis, to help assess the risk of progression to rheumatoid arthritis.

What anti-CCP is and what it shows

Rheumatoid arthritis is a chronic autoimmune inflammatory disease: the immune system attacks the joint lining, and without treatment the inflammation gradually damages cartilage and bone. Many affected people have antibodies to citrullinated proteins (ACPA) in their blood, and the anti-CCP test is the most common way of measuring them.

Anti-CCP is highly specific: it is rarely positive in people without rheumatoid arthritis. Its sensitivity is moderate, so it is positive in approximately two-thirds of affected people. The antibodies are often present early in the disease and may appear years before the first symptoms. Positive anti-CCP is also associated with a more severe disease course and greater susceptibility to joint damage.

Anti-CCP and rheumatoid factor are part of the 2010 ACR/EULAR classification criteria, together with the number of affected joints, duration of symptoms and inflammatory markers such as CRP and erythrocyte sedimentation rate.

Anti-CCP is not a test for people without symptoms or for monitoring treatment. A doctor monitors disease activity through joint examination and inflammatory markers.

Preparation and sample

Blood is taken from a vein. You do not need to fast, and no special preparation is required. If you take biotin (for example, hair and nail supplements), mention this when your blood is drawn.

How to interpret the result

The result is expressed in units per millilitre (U/mL) and compared with a cut-off value that depends on the method and is printed on the report. A value below the cut-off means a negative result, and a value above it means a positive one. The ACR/EULAR criteria distinguish a low-positive result, up to three times the cut-off value, and a high-positive result, above three times the cut-off value.

The result alone does not establish a diagnosis; a doctor, usually a rheumatologist, does so based on examination, symptoms, laboratory results and, if needed, joint ultrasound or X-rays. Anti-CCP is less commonly positive in other diseases, such as psoriatic arthritis. How it is interpreted together with rheumatoid factor:

Anti-CCP	Rheumatoid factor	What it most often means
positive	positive	with typical symptoms, a high probability of rheumatoid arthritis
positive	negative	possible rheumatoid arthritis, particularly early in the disease
negative	positive	RF is less specific: it is also elevated in other autoimmune diseases, chronic infections and some healthy older people
negative	negative	rheumatoid arthritis is less likely, but not ruled out

How to arrange testing

You can have blood taken without an appointment or referral at one of our branches across Croatia (listed under Contact). Prices for all tests and panels, including rheumatoid factor and CRP, which are often measured alongside anti-CCP, are listed in the service price list.

Frequently asked questions

What are the anti-CCP reference values?

There is no single cut-off for all laboratories, because it depends on the method. The cut-off is printed alongside the result on the report: below it the result is negative, and above it positive. Results from different laboratories should therefore not be compared by numbers alone.

What does positive anti-CCP mean?

It means that antibodies typical of rheumatoid arthritis were found in the blood. Alongside painful and swollen joints, this is a strong indicator of the disease, and the result should be shown to a doctor as soon as possible, because early treatment slows joint damage. A positive result without symptoms does not mean you have rheumatoid arthritis, but your doctor may recommend follow-up.

Can anti-CCP be negative if I have rheumatoid arthritis?

Yes. Approximately one-third of affected people do not have these antibodies, so diagnosis is not based on the result alone. Joint examination, symptom duration, rheumatoid factor, inflammatory markers and imaging are decisive.

Does anti-CCP need repeating?

Usually not for monitoring disease, because antibody levels do not track disease activity or treatment success. Even with a negative result, repeating it rarely changes the conclusion, so your doctor decides according to symptoms.