title: Anti-cyclic citrullinated peptide antibodies: a comparison of different assays for the diagnosis of rheumatoid arthritis.
abstract: OBJECTIVE
  Anti-cyclic citrullinated peptide (anti-CCP) antibodies are highly specific markers of rheumatoid arthritis (RA). Considering the heterogeneity of the target antigens involved, and the test platforms and conjugates proposed in commercial anti-CCP assays, we assessed the diagnostic performances of four fully automated anti-CCP assays in a cohort of patients with RA compared to patients with other autoimmune and inflammatory disorders. We also evaluated the agreement between the qualitative results of these immunoassays.
  
  
  METHODS
  We evaluated three anti-CCP2 assays [Eurodiagnostica enzyme-linked immunosorbent assay (ELISA), Elecsys electrochemiluminescence immunoassay (ECLIA) on the Modular E170 Analyzer, and Zenit chemiluminescence immunoassay (CLIA) on the Zenit RA Analyzer] and one anti-CCP3 assay (Inova ELISA). ELISAs were performed on an automated workstation. Samples from 112 patients with RA and a disease control group of 136 patients (53 with autoimmune diseases, 65 non-autoimmune disorders, and 18 infectious diseases) were studied (included 161 samples submitted consecutively to the laboratory).
  
  
  RESULTS
  At a fixed specificity of 92%, the anti-CCP3 assay presented the highest sensitivity (75%) compared to the anti-CCP2 assays evaluated (63-72%). The Zenit anti-CCP2 assay gave the most false-positive results (especially in patients with viral infections and connective tissue diseases). The agreement between assays ranged from 86.3% to 95.2% and Kappa coefficients ranged from 0.724 to 0.899.
  
  
  CONCLUSIONS
  Recently released automated workstations provide a valuable alternative to ELISA to diagnose RA. However, differences in diagnostic performances are highlighted in our experience, especially for the Zenit assay. In our cohort, the anti-CCP3 assay gave slightly better performances than the anti-CCP2 assays (with the exception of the Zenit assay).
authors.affiliation: Laboratory of Immunology, Brugmann University Hospital, the Free University of Brussels, Brussels, Belgium. fdebaugn@ulb.ac.be
authors.forename: F
authors.initials: F
authors.lastname: Debaugnies
authors.forename: G
authors.initials: G
authors.lastname: Servais
authors.forename: V
authors.initials: V
authors.lastname: Badot
authors.forename: D
authors.initials: D
authors.lastname: Noubouossie
authors.forename: D
authors.initials: D
authors.lastname: Willems
authors.forename: F
authors.initials: F
authors.lastname: Corazza
mesh_terms: D000328:Adult; D000368:Aged; D001172:Arthritis, Rheumatoid / Q000175:diagnosis* / Q000276:immunology; D001323:Autoantibodies / Q000097:blood*; D001681:Biological Assay / Q000379:methods; D016022:Case-Control Studies; D015331:Cohort Studies; D004797:Enzyme-Linked Immunosorbent Assay / Q000379:methods*; D005189:False Positive Reactions; D005260:Female; D006801:Humans; D008163:Luminescent Measurements / Q000379:methods*; D008297:Male; D008875:Middle Aged; D010456:Peptides, Cyclic / Q000276:immunology*; D012680:Sensitivity and Specificity
chemical_list: D001323:Autoantibodies; D010456:Peptides, Cyclic; C487763:cyclic citrullinated peptide