title: Comparative performance analysis of 4 different anti-citrullinated protein assays in the diagnosis of rheumatoid arthritis.
abstract: OBJECTIVE
  To evaluate the diagnostic performances of 2 recently developed assays, third-generation anti-cyclic citrullinated peptide (anti-CCP3) and anti-mutated citrullinated vimentin (anti-MCV), in comparison to conventional second-generation anti-cyclic citrullinated peptide (anti-CCP2) assay; and to assess a novel fully automated, random-access AxSYM anti-CCP assay for early diagnosis of rheumatoid arthritis (RA).
  
  
  METHODS
  A cohort of 176 patients was enrolled in our study; 93 were diagnosed as having RA. The non-RA group consisted of 83 patients including 38 with systemic lupus erythematosus, 17 with primary Sjögren's syndrome, 11 with osteoarthritis, and 17 healthy controls. All were tested for presence of anti-CCP2, anti-CCP3, AxSYM anti-CCP, anti-MCV, and rheumatoid factor (RF)-IgM according to the manufacturers' instructions.
  
  
  RESULTS
  Diagnostic performance of the assays revealed the highest area under the curve for the novel AxSYM anti-CCP [89.1; 95% confidence interval (CI) 84.3-93.8], followed by anti-CCP3 (86.7; 95% CI 81.6-91.9), anti-CCP2 (82; 95% CI 75.8-88.3), and anti-MCV (71.9; 95% CI 64.4-79.5). The sensitivities and specificities were 60.2% and 98.8% for anti-CCP2, 61.3% and 97.6% for anti-CCP3, 80.6% and 84.3% for AxSYM anti-CCP, 49.8% and 91.6% for anti-MCV, and 67.8% and 91.6% for RF-IgM, respectively.
  
  
  CONCLUSIONS
  At cutoff of 5 U/ml, AxSYM anti-CCP emerged as a highly sensitive first-line early diagnostic tool for RA, with the greatest discrimination power, above 16 U/ml, in case of positive result. Using a single easily performed automated assay at 2 determined decision limits we were able to diagnose 81% of cases of RA and missing only 1.2%.
authors.affiliation: Department of Biochemistry, Yeditepe University Hospital, Devlet Yolu Ankara, Caddesi, 34752 Istanbul, Turkey. nilgunm@yeditepe.edu.tr
authors.forename: Nilgun
authors.initials: N
authors.lastname: Mutlu
authors.forename: Muge
authors.initials: M
authors.lastname: Bicakcigil
authors.forename: Demet A
authors.initials: DA
authors.lastname: Tasan
authors.forename: Ayhan
authors.initials: A
authors.lastname: Kaya
authors.forename: Sule
authors.initials: S
authors.lastname: Yavuz
authors.forename: A Inci
authors.initials: AI
authors.lastname: Ozden
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001172:Arthritis, Rheumatoid / Q000175:diagnosis* / Q000276:immunology; D001323:Autoantibodies / Q000032:analysis*; D016022:Case-Control Studies; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D010456:Peptides, Cyclic / Q000276:immunology*; D012680:Sensitivity and Specificity; D055815:Young Adult
chemical_list: D001323:Autoantibodies; D010456:Peptides, Cyclic; C487763:cyclic citrullinated peptide