Comparison of nine second-and third-generation anti-cyclic citrullinated peptide antibody assays for the diagnosis of rheumatoid arthritis

The aim of this study was to compare the diagnostic and analytical performances of nine anti-cyclic citrullinated peptide (CCP) antibody assays. Anti-CCP antibody titers were measured in sera from 89 patients with rheumatoid arthritis (RA), 121 with rheumatic diseases other than RA (non-RA), 47 with osteoarthritis (OA), 142 with chronic inflammatory diseases (CID) and 168 healthy subjects. Reproducibility, sensitivity, specificity, correlation and concordance rate of the nine assays were compared. Coeficients of variations of within-run and between-run reproducibility at two different concentrations for each assay ranged from 0.7 to 8.5% and from 0.6 to 8.3%, respectively. With our proposed optimal cut-oFF value for the third-generation assay, concordance rates were 96.8~99.6%. The range of sensitivity was 75.3~78.7% and the ranges of specificity for non-RA, OA, CID, and healthy subjects were 93.4~97.5%, 97.9%, 96.5~98.6% and 98.8~100%, respectively. However, several discrepant samples were detected and their titer levels were about 3 times higher than the normal upper limit in the 2010 RA classification criteria. Good positive correlations were observed for parts of the second-generation assay. Our study showed that each of the nine assays has good reproducibility and high diagnostic accuracy, and is thus equally useful for the diagnosis of RA.