title: Performance evaluation of a novel chemiluminescence assay for detection of anti-GBM antibodies: an international multicenter study.
abstract: BACKGROUND
  Autoantibodies to the non-collagen region (NC1) of the alpha-3 subunit of collagen IV represent a serological hallmark in the diagnosis of Goodpasture's syndrome (GPS). The objective of our study was to carefully analyze the performance characteristics of a novel anti-glomerular basement membrane (GBM) chemiluminescence immunoassay (CIA).
  
  
  METHODS
  Sera from patients with GPS (n = 90) were collected from four clinical centers. Samples from different disease groups (n = 397) and healthy individuals (n = 400) were used as controls. All samples were tested for anti-GBM antibodies by a rapid, random access CIA (QUANTA Flash™ GBM). Most of the samples were also tested using other methods including different commercial anti-GBM IgG assays and research assays for anti-GBM IgA and IgM.
  
  
  RESULTS
  The sensitivity and specificity of the novel CIA was 95.6% [95% confidence interval (CI) 89.0-98.8%] and 99.6% (95% CI 98.9-99.9%), respectively. Receiver operating characteristic analysis showed good discrimination between GPS patients and controls. The area under the curve was 0.98 (CI 0.96-1.0). The three anti-GBM antibody-positive samples from the control group were from two healthy individuals and one human immunodeficiency virus (HIV)-infected patient. All three individuals had low levels of anti-GBM antibodies [20, 24 and 25 chemiluminescent unit (CU), cutoff 20 CU]. When the results of the new CIA were compared to other methods, good agreement was observed: 95.8% (kappa = 0.92) versus EliA™ GBM, 97.4% (kappa = 0.95) versus both BINDAZYME™ Anti-GBM and QUANTA Lite® GBM. Anti-GBM IgA was detectable in low concentrations in patients with GPS and was associated with anti-GBM IgG but was less useful in discriminating GPS patients and controls. No discrimination was found for anti-GBM IgM.
  
  
  CONCLUSIONS
  The novel QUANTA Flash™ GBM CIA demonstrated good sensitivity and specificity and had good agreement with other methods. Our data confirm that ∼5% of patients with GPS do not have detectable levels of anti-GBM antibodies.
authors.affiliation: INOVA Diagnostics, INC. San Diego, CA, USA. mmahler@inovadx.com
authors.forename: Michael
authors.initials: M
authors.lastname: Mahler
authors.forename: Antonella
authors.initials: A
authors.lastname: Radice
authors.forename: Renato A
authors.initials: RA
authors.lastname: Sinico
authors.forename: Jan
authors.initials: J
authors.lastname: Damoiseaux
authors.forename: Andrea
authors.initials: A
authors.lastname: Seaman
authors.forename: Kristen
authors.initials: K
authors.lastname: Buckmelter
authors.forename: Alenka
authors.initials: A
authors.lastname: Vizjak
authors.forename: Carol
authors.initials: C
authors.lastname: Buchner
authors.forename: Walter L
authors.initials: WL
authors.lastname: Binder
authors.forename: Marvin J
authors.initials: MJ
authors.lastname: Fritzler
authors.forename: Zhao
authors.initials: Z
authors.lastname: Cui
mesh_terms: D019867:Anti-Glomerular Basement Membrane Disease / Q000175:diagnosis* / Q000276:immunology; D001323:Autoantibodies / Q000097:blood* / Q000276:immunology; D016022:Case-Control Studies; D024141:Collagen Type IV / Q000276:immunology; D050533:Glomerular Basement Membrane / Q000276:immunology*; D006801:Humans; D007118:Immunoassay / Q000379:methods*; D007390:International Agencies; D008163:Luminescent Measurements / Q000379:methods*; D011379:Prognosis; D012680:Sensitivity and Specificity
chemical_list: D001323:Autoantibodies; D024141:Collagen Type IV; C051951:antiglomerular basement membrane antibody