Evaluation of three automated enzyme immunoassays for detection of anti-cyclic citrullinated peptide antibodies in qualitative and quantitative aspects

Objective: The anti-cyclic citrullinated peptide (anti-CCP) antibody has been increasingly used in the field of rheumatology, and various manufacturers have developed a variety of anti-CCP assays using mainly ELISA techniques. This study evaluated the performance of recently marketed automated chemiluminescence enzyme immunoassays for anti-CCP. Methods: We investigated four anti-CCP assays (Diastat anti-CCP ELISA assay, Axsym anti-CCP assay on the Axsym system, the Architect anti-CCP assay on the Architect i2000 system and the Elecsys anti-CCP assay on the Cobas e 411 analyzer). Samples from 64 patients with RA and 152 controls, including patients with various autoimmune diseases, were studied. We assessed the clinical sensitivities and specificities, and compared the qualitative and quantitative results of each anti-CCP assay. Results: Using the manufacturers' cut-off, diagnostic sensitivities ranged from 90.6 to 93.8% and the specificities ranged from 85.5 to 86.8%. The areas under the curve were comparable among the different assays, and qualitative agreements ranged from 97.2 to 99.1%. In the quantitative results, all anti-CCP assays were significantly correlated (P<0.001), but the correlation coefficient ranged from 0.615 to 0.861. Especially, the correlation coefficients between the automated anti-CCP assays were higher than those between the ELISA assay (Diastat) and the automated assays. Conclusions: The overall diagnostic performance of the automated anti-CCP assays was comparable, and it provides reliable information on antibody levels, making them useful in monitoring disease activity.