title: Diagnostic usefulness of a third-generation anti-cyclic citrulline antibody test in patients with recent-onset polyarthritis.
abstract: BACKGROUND
  The high specificity of anti-cyclic citrullinated peptide antibodies (anti-CCP) helps substantially in the diagnosis of rheumatoid arthritis (RA), combined with classical markers such as rheumatoid factor (RF). The recent introduction of third-generation methods (anti-CCP3) for anti-CCP detection could further improve diagnostic efficiency. The aim of this study was to determinate the diagnostic efficiency (sensitivity and specificity) of anti-CCP using a new anti-CCP3 method and to compare it with the previous second-generation method (anti-CCP2).
  
  
  METHODS
  Anti-CCP were studied in sera of 234 patients with recent-onset polyarthritis (ROP) (age > or =16 years; evolution time > or =4 weeks < or =1 year; 2 or more inflamed joints, without drug therapy). After 1 year, 124 patients were diagnosed with RA (American College of Rheumatology criteria). Two ELISAs, an anti-CCP2 and an anti-CCP3, were performed.
  
  
  RESULTS
  The best sensitivity according to receiver operating characteristic curves was 51.5% and 54.8% for anti-CCP3 and anti-CCP2, with a specificity of 96.2% and 98.1%, respectively (optimal cutoffs 14.2 and 18.7 U/mL). Significant correlations were obtained (p<0.001) when the methods were compared to each other and to RF.
  
  
  CONCLUSIONS
  Testing with both types of anti-CCP kit is highly specific for the presence of RA. In our ROP group, anti-CCP2 and anti-CCP3 exhibited similar diagnostic efficiency.
authors.affiliation: Department of Immunology, University Hospital Virgen del Rocío, Sevilla, Spain. joseluiscaro@hotmail.com
authors.forename: José
authors.initials: J
authors.lastname: Luis Caro-Oleas
authors.forename: Antonio
authors.initials: A
authors.lastname: Fernández-Suárez
authors.forename: Sonsoles
authors.initials: S
authors.lastname: Reneses Cesteros
authors.forename: Carmen
authors.initials: C
authors.lastname: Porrino
authors.forename: Antonio
authors.initials: A
authors.lastname: Núñez-Roldán
authors.forename: Ingeborg
authors.initials: I
authors.lastname: Wichmann Schlipf
mesh_terms: D000328:Adult; D001168:Arthritis / Q000175:diagnosis* / Q000276:immunology*; D001323:Autoantibodies / Q000097:blood*; D015415:Biomarkers / Q000097:blood; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D010456:Peptides, Cyclic / Q000276:immunology*; D012217:Rheumatoid Factor / Q000097:blood*; D012680:Sensitivity and Specificity
chemical_list: D001323:Autoantibodies; D015415:Biomarkers; D010456:Peptides, Cyclic; C487763:cyclic citrullinated peptide; D012217:Rheumatoid Factor