title: A novel high sensitivity ELISA for detection of antineutrophil cytoplasm antibodies against proteinase-3.
abstract: OBJECTIVE
  Conventional direct enzyme-linked immunosorbent assays (ELISA) for the detection of anti-neutrophil cytoplasm antibodies (ANCA) often lack sensitivity because epitopes of the target antigen are hidden by binding to the ELISA plate. This study was designed to evaluate a novel ELISA method for detection of ANCA against proteinase-3 (PR3) for the diagnosis of Wegener's granulomatosis (WG) using PR3 presented in its native form.
  
  
  METHODS
  Sera from four subgroups of patients with a diagnosis of WG (n=86), 80 healthy controls and 450 disease controls were tested for the presence of C-ANCA/PR3-ANCA by anchor ELISA, direct ELISA, capture ELISA, indirect immunofluorescence (IFT) and immunoblotting.
  
  
  RESULTS
  In prospectively analysed consecutive patients, anchor ELISA showed the highest sensitivity for a diagnosis of WG of 96.0% (95% CI: 79.6-99.3), followed by IFT 92.0% (73.9-98.8), capture ELISA 72.0 (50.6-87.9) and direct ELISA 60.0 (38.7-78.8). Specificity was high for all methods and ranged from 98.5 (97.0-99.4) to 95.5% (97.9-99.8). Receiver operating characteristics curve analysis revealed that the overall diagnostic performance of the anchor ELISA was significantly superior compared to the direct ELISA and the capture ELISA in patients with generalized WG, and also compared to IFT and immunoblotting in patients with localised WG.
  
  
  CONCLUSIONS
  Anchor ELISA is a novel highly sensitive and specific method for the detection of PR3-ANCA in patients with WG, which may replace the need for a combined analysis with IFT and ELISA in the future.
authors.affiliation: Poliklinik fur Rheumatologie, Universitätsklinikum Schleswig-Holstein, Campus Lübeck & Rheumaklinik Bad Bramstedt, Rheumaklinik Bad Bramstedt, Germany. hellmich@rheuma-zentrum.de
authors.forename: B
authors.initials: B
authors.lastname: Hellmich
authors.forename: E
authors.initials: E
authors.lastname: Csernok
authors.forename: G
authors.initials: G
authors.lastname: Fredenhagen
authors.forename: W L
authors.initials: WL
authors.lastname: Gross
mesh_terms: D019268:Antibodies, Antineutrophil Cytoplasmic / Q000097:blood*; D001324:Autoantigens / Q000276:immunology; D015415:Biomarkers / Q000097:blood; D004797:Enzyme-Linked Immunosorbent Assay / Q000379:methods*; D005260:Female; D019084:Fluorescent Antibody Technique, Indirect; D014890:Granulomatosis with Polyangiitis / Q000175:diagnosis / Q000276:immunology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D053146:Myeloblastin / Q000276:immunology*; D011446:Prospective Studies; D012372:ROC Curve; D012680:Sensitivity and Specificity
chemical_list: D019268:Antibodies, Antineutrophil Cytoplasmic; D001324:Autoantigens; D015415:Biomarkers; D053146:Myeloblastin