title: 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.
authors.affiliation: Translational Medicine Research Center, School of Pharmaceutical Sciences, Xiamen University , Xiamen, Fujian , P. R. China.
authors.forename: Huiming
authors.initials: H
authors.lastname: Ye
authors.forename: Falin
authors.initials: F
authors.lastname: Chen
authors.forename: Shuidi
authors.initials: S
authors.lastname: Yan
authors.forename: Yan
authors.initials: Y
authors.lastname: Zhang
authors.forename: Zanxi
authors.initials: Z
authors.lastname: Fang
authors.forename: Xiaosong
authors.initials: X
authors.lastname: Su
authors.forename: Weicheng
authors.initials: W
authors.lastname: Cai
authors.forename: Zhongying
authors.initials: Z
authors.lastname: Zhang
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001172:Arthritis, Rheumatoid / Q000097:blood / Q000175:diagnosis* / Q000276:immunology; D001323:Autoantibodies / Q000097:blood*; D002097:C-Reactive Protein / Q000378:metabolism; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D010456:Peptides, Cyclic / Q000276:immunology*; D012217:Rheumatoid Factor / Q000097:blood; D012680:Sensitivity and Specificity; D055815:Young Adult
chemical_list: D001323:Autoantibodies; D010456:Peptides, Cyclic; C487763:cyclic citrullinated peptide; D002097:C-Reactive Protein; D012217:Rheumatoid Factor
keywords: Anti-cyclic citrullinated peptide antibodies; Diagnostic marker; Electrochemiluminescence immunoassay; Rheumatoid arthritis; Rheumatoid factor