Anti-citrullinated protein/peptide antibodies (ACPAs) are autoantibodies frequently detected in rheumatoid arthritis patients. During inflammation, citrulline is incorporated enzymatically into proteins, what is called citrullination. Recently, these ACPAs have turned up as powerful biomarkers, which are accepted as a major diagnostic tool in diagnosing rheumatoid arthritis (RA) already in a very early stage of disease.

Anti-CCP antibodies are member of ACPA family,"Cyclic citrullinated peptide" is also known as "CCP". It is a cyclic peptide incorporating the amino acid citrulline.citrulline is incorporated enzymatically into proteins, what is called citrullination. Recently, these ACPAs have turned up as powerful biomarkers, which are accepted as a major diagnostic tool in diagnosing rheumatoid arthritis (RA) already in a very early stage of disease.