Diagnostic utility of the Elecsys anti-CCP assay in patients with rheumatoid arthritis

Abstract

Objective. The automatic anti-cyclic citrullinated peptide (anti-CCP) antibodies assay offered great advantages over traditional methods in terms of improved precision, reliability, technical simplicity, short turnaround time and high-speed throughput. In this study, we evaluated the main technical performance and diagnostic accuracy of the first automatic anti-CCP assay approved in China.

Methods. The study comprised 106 rheumatoid arthritis (RA) patients, 203 non-RA rheumatic disease controls and 46 healthy persons. Anti-CCP, rheumatoid factor (RF), α₁-acid glycoprotein, C-reactive protein and erythrocyte sedimentation rate were measured and compared. The precision, reference intervals for Chinese population and cut-off value for RA diagnosis, as well as the suitable diluent for anti-CCP were assessed. The positive rate and score of anti-CCP were compared with RF and acute-phase reactants, according to the new RA criteria.

Results. Within- and between-run imprecision, expressed as the coefficient of variation, were 0.47–1.36% and 1.15–2.63%, respectively. Upper 95% reference limit of anti-CCP in healthy Chinese was 8.8 U/mL. The area under curve of the receiver operating characteristic(ROC) for anti-CCP and RF were 0.882 (95% CI 0.833–0.930) and 0.844 (95% CI 0.792–0.897), respectively. Based on the cut-off value set by ROC, compared to RF, anti-CCP had higher sensitivity (96.8% vs. 78.3%) and specificity (90.9% vs. 70.7%). With 17 U/mL set as the optimal cut-off for anti-CCP, the total positivity of anti-CCP was comparable to that of RF (76.4% vs. 75.5%), but the high-positivity rate of anti-CCP was significantly higher (74.5% vs. 62.3%, p < 0.005).

Conclusions. Our results confirm anti-CCP as a more sensitive and specific marker than RF for the diagnosis of RA. The diagnostic performance of the Elecsys anti-CCP assay makes it a useful adjunct to clinical practice in the Chinese population.

Keywords:

• Anti-cyclic citrullinated peptide antibodies
• Diagnostic marker
• Electrochemiluminescence immunoassay
• Rheumatoid arthritis
• Rheumatoid factor

Acknowledgements

The authors thank professor Chi-Meng Tzeng in Translational Medicine Research Center, School of Pharmaceutical Sciences, Xiamen University for providing innovative suggestion and for help with the manuscript.

Funding

This study was supported partly by National Natural Science Foundation of China (Grant No. 8110331).

Conflict of interest None.