title: Measurement characteristics of a new rapid anti-CCP2 test compared to the anti-CCP2 ELISA.
abstract: OBJECTIVE
  Anti-cyclic citrullinated peptide (CCP)2 antibody status is an important diagnostic tool in the work-up of undifferentiated arthritis (UA)/early rheumatoid arthritis (RA) but the results of the enzyme-linked immunosorbent assay (ELISA) are only available a few days after the test. The aim of this study was to assess the measurement characteristics of a rapid anti-CCP2 test compared to the usual anti-CCP2 ELISA test.
  
  
  METHODS
  In the first phase, rapid anti-CCP2 (CCPoint) tests were performed in capillary blood obtained by finger puncture (CAP), in venous blood from a clot tube (CLOT) and in serum (SERUM) in consenting RA patients. Anti-CCP2 measured in serum using the anti-CCP2 ELISA (ELISA) was set as the gold standard (reference). In the second phase of the study, specificity versus RA was confirmed in consenting non-RA patients and healthy controls. The anti-CCP2 results were negative (no visible line or anti-CCP2<25 U/mL) or positive (visible line or anti-CCP2> or =25 U/mL).
  
  
  RESULTS
  A total of 880 subjects (109 RA patients, 351 non-RA patients and 420 healthy controls) were enrolled in this study. For the RA patients, 5%, 15%, and 1% of CAP, CLOT and SERUM tests, respectively, were inconclusive. The sensitivity and specificity of CAP compared with ELISA were 95% (95% CI 90-100) and 95% (95% CI 89-100), respectively, and the corresponding values for SERUM were 97% (95% CI 93-100) and 98 (95% CI 94-100). The specificity for RA versus non-RA and healthy controls was 99% (95% CI 97-100) and 99% (95% CI 98-100), respectively.
  
  
  CONCLUSIONS
  The CCPoint test is a fast, valid and reliable anti-CCP2 test in both capillary blood and serum but not directly in venous blood.
authors.affiliation: Department of Rheumatology, Sint Maartenskliniek, Nijmegen, The Netherlands. g.snijders@maartenskliniek.nl
authors.forename: G F
authors.initials: GF
authors.lastname: Snijders
authors.forename: A A den
authors.initials: AA
authors.lastname: Broeder
authors.forename: K
authors.initials: K
authors.lastname: Bevers
authors.forename: M E
authors.initials: ME
authors.lastname: Jeurissen
authors.forename: J E
authors.initials: JE
authors.lastname: van Eerd
authors.forename: F H J
authors.initials: FH
authors.lastname: van den Hoogen
mesh_terms: D000328:Adult; D000368:Aged; D000888:Antibodies, Anti-Idiotypic / Q000097:blood*; D001172:Arthritis, Rheumatoid / Q000097:blood / Q000276:immunology; D016022:Case-Control Studies; D003955:Diagnostic Tests, Routine / Q000379:methods*; D018450:Disease Progression; D004797:Enzyme-Linked Immunosorbent Assay / Q000379:methods*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D010456:Peptides, Cyclic / Q000276:immunology*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity
chemical_list: D000888:Antibodies, Anti-Idiotypic; D010456:Peptides, Cyclic; C487763:cyclic citrullinated peptide