[Cyclic citrullinated peptide antibodies (anti-CCP) together with some other parameters used for serologic diagnosis...

Rheumatoid arthritis (RA) is one of the most common rheumatic disease, which is primarily diagnosed by clinical history, physical examination, and laboratory tests, including a large number of biochemical and biologic markers. Recently, it has been shown that the amino acid citrulline, which is a unit of filaggrin, is a substantial component of the antigenic epitope, and enzyme immunoassays which use synthetic citrullinated peptide are highly effective tests for the detection of autoantibodies against cyclic citrullinated peptide (CCP), which are a new a highly specific marker for RA. The aim of this study was to investigate the presence of anti-CCP antibodies in RA suspected patients and to evaluate the combination of these autoantibodies with some other serologic markers such as IgM-rheumatoid factor (IgM-RF), C-reactive protein (CRP) and antinuclear antibodies (ANAs). For this purpose, the concentrations of RF and CRP were determined by quantitative immunonephelometry, titres of ANAs by indirect immunofluorescence, and presence of anti-CCP by a commercial semiquantitative microELISA method, in 88 patients with clinically suspected RA, as well as 42 sex- and age-matched healthy blood donors. As a result, the high levels of IgM-RF and CRP were found in 48 (54.5%) and 49 (55.7%) of the patients, respectively, while 47 (53.4%) and 25(28.4%) patients were found positive for ANAs and anti-CCP, respectively. Of 48 RF positive patients, 25 were also positive for anti-CCP, and the distribution rates of the markers in 25 anti-CCP positive patients were as follows; 100% for RF, 84% for CRP and 52% for ANA. The sensitivity of anti-CCP ELISA was 52.1% and specificity was 100%, when evaluated according to RF positivity as a main serologic marker of RA. In conclusion, anti-CCP antibody testing may be useful in the serologic diagnosis of RA patients, especially in combination with RF, however more detailed follow-up clinical studies on the large number of patients with established RA, would be needed for our country.