Anti-CCP antibodies
The most specific blood test for rheumatoid arthritis. Unlike rheumatoid factor, a positive anti-CCP rarely appears without RA — and it can turn positive years before the joints, marking people at high risk and predicting more aggressive disease.
What it measures
Anti-CCP (antibodies to cyclic citrullinated peptides, also called ACPA) targets proteins that have been chemically modified by citrullination — a process amplified in rheumatoid joints. Its great strength is specificity: around 95% specific for rheumatoid arthritis, so a positive result strongly points to RA and rarely to anything else. Its sensitivity is similar to rheumatoid factor (~60–70%), so it can be negative in true RA. Crucially, anti-CCP can appear years before joint symptoms, identifying people at high risk, and a positive result predicts more erosive, aggressive disease that benefits from earlier, more intensive treatment. It is now central to the classification criteria for RA and is checked together with rheumatoid factor.
What a high value can mean
- Rheumatoid arthritis — a positive result is ~95% specific; strongly supports the diagnosis.
- High titres — predict more aggressive, erosive, joint-damaging disease.
- Pre-clinical RA — can be positive years before symptoms, flagging high risk.
- Occasionally — a small number of other autoimmune conditions or, rarely, chronic infection; far less often than rheumatoid factor.
What a low value can mean
- Negative / normal — does not exclude RA (seronegative RA exists), but makes it less likely.
- A negative anti-CCP with a positive RF — less specific; the picture is weighed clinically.
When to discuss with a doctor
Anti-CCP is the test to add when inflammatory arthritis is suspected — persistent symmetrical joint pain and swelling with morning stiffness — because a positive result both confirms RA more reliably than RF and flags the aggressive disease that needs early rheumatology care. A positive anti-CCP, even with few current symptoms, should prompt specialist review, as starting disease-modifying treatment early prevents irreversible joint damage. A negative result in someone with clear inflammatory joints does not rule RA out. Mediora.AI shows anti-CCP with rheumatoid factor, ESR and CRP so the combined pattern is read; the diagnosis and treatment belong with rheumatology.