Evaluation of the Usefulness of Anti-Cyclic Citrullinated Peptide Antibodies Measured by an Automated Enzyme Immunoassay

Kim, Hye Ran; Shin, Jeong Whan; Lee, Jeong Nyeo

Abstract

BACKGROUND: Rheumatoid arthritis (RA) is the most common autoimmune rheumatic disease, but sensitive and specific test for its diagnosis is lack. This study evaluated the analytical performance and diagnostic role of a new automated ELISA anti-cyclic citrullinated peptide (anti-CCP) antibody test.
METHODS
Anti-CCP antibody test was done with the enzyme-linked immunosorbent assay (ELISA) in serum samples from 49 RA patients and 104 non-RA patients, and 51 healthy subjects. Serum pools were used to determine its precision and linearity. The optimal cut-off values were determined by the receiver-operator characteristics (ROC) curve. The rheumatoid factor (RF) by turbidimetry was also assayed in every samle and the results were compared to anti-CCP for sensitivity and specificity.
RESULTS
The total imprecision (CV%) was 4.8%, 7.6% for serum pools with low (mean concentration: 2.7 U/mL) and high (mean concentration :82.2 U/mL) concentration, respectively. Linearity data were acceptable (R2=0.9907). At each optimal cut-off value, the sensitivity of anti-CCP was higher than that of RF (81.6 % vs 69.4%), but statistical significance was not defined. Specificity of anti-CCP was higher than that of RF (95.5% vs 75.5%, p<0.001). A combination of anti-CCP and RF increased sensitivity and specificity to 87.7%, 98.0%, respectively. Nine of 15 (60.0%) sera from RF negative RA patients were positive for anti-CCP.
CONCLUSIONS
Anti-CCP ELISA antibody test, we examined on a fully automated enzyme immunoassay, is easy to assay in routine laboratory, and showed good analytical performance. And anti-CCP antibody test also showed higher diagnostic specificity than RF. So, anti-CCP antibody may be useful serologic marker for diagnosis and monitoring of RA, if performed concomitantly with RF assay.