ABSTRACT
The determination of anti-cyclic citrullinated peptide antibodies (anti-CCP) is an extremely useful laboratory test in the differential diagnosis of patients in which Rheumatoid Arthritis (RA) is suspected. Citrullination is an unspecific protein modification associated to inflammation. The production of antibodies directed against citrullinated antigens in the synovial membrane is, on the contrary, specific for RA, for which important associations between these and the pathogen of the disease have been described. This review focuses on the different characteristics that make this test routinely asked for in clinical practice: high specificity; high positive predictive value in undifferentiated arthritis; early manifestation, development prior to clinical disease, and its association with a more aggressive course of the disease.