Anti-citrullinated protein antibodies as biomarkers in rheumatoid arthritis.

ACPAs have high diagnostic sensitivity and specificity for RA and recognize citrullinated epitopes from several proteins. The best-performing single epitope is from Epstein-Barr Virus nuclear antigen 2 and a major proportion of the antibodies recognize a central citrulline residue commonly associated with a Cit-Gly motif located in a flexible peptide structure. In addition, ACPAs may also have prognostic value, especially in relation to early treatment, although ACPAs main function is to aid in the diagnosis of RA.