Anti-citrullinated protein antibody

Anti-citrullinated protein antibodies (ACPA) or anti-cyclic citrullinated protein antibodies (anti-CCP) are autoantibodies (antibodies against human tissues) frequently detected in rheumatoid arthritis. The main epitope for these antibodies is filaggrin, and there is cross-reactivity between ACPA and anti-keratin and anti-perinuclear factor. In a comparative study, various detection kits had a sensitivity between 69.6% and 77.5% and a specificity between 87.8% and 96.4%. Given that ACPA is more specific than rheumatoid factor, it is used to distinguish various causes of arthritis.