Performance characteristic of anti-cyclic citrullinated peptide (CCP) assay on Korean rheumatoid arthritis (RA) patients and healthy controls.

The objective of this study was to evaluate the performance of the established anti-cyclic citrullinated peptide (anti-CCP) enzyme-linked immunosorbent assay (ELISA) compared to Rheumatoid Factor-Immunoglobulin M (RF-IgM) and C - reactive protein (CRP). Serum samples of 176 patients were analyzed with the anti-CCP ELISA assay method established in our laboratory. The results of rheumatoid arthritis (RA) patients, the other inflammatory patients, and healthy controls were compared using MedCalc (version 7.0). The anti-CCP assay results were compared with RF-IgM and CRP concentration analyzed in Catholic University. The specificity of ELISA test results of RA patients showed 91% and 87%, when healthy controls or osteoarthritis patients were considered as negative. Thus, the established ELISA method was RA specific, but its sensitivity was low. To see the low sensitivity may from aging effect, the concentration of anti-CCP was analyzed for different aging group. We tested 110 healthy controls' sera using the same method. The statistical results of young subjects (<45 years old) showed significantly lower anti-CCP concentrations than those of older subjects (>65 years old, p<0.0001). The citrullination might also be occurring during aging process in healthy populations. The validation results imply that the established method could be used as a clinical diagnostic for RA together with RF-IgM.