title: Diabetes antibody standardization program: first proficiency evaluation of assays for autoantibodies to zinc transporter 8.
abstract: BACKGROUND
  Zinc transporter 8 (ZnT8) is a recently identified major autoantigen in type 1 diabetes, and autoantibodies to ZnT8 (ZnT8A) are new markers for disease prediction and diagnosis. Here we report the results of the first international proficiency evaluation of ZnT8A assays by the Diabetes Antibody Standardization Program (DASP).
  
  
  METHODS
  After a pilot workshop in 2007, an expanded ZnT8A workshop was held in 2009, with 26 participating laboratories from 13 countries submitting results of 63 different assays. ZnT8A levels were measured in coded sera from 50 patients with newly diagnosed type 1 diabetes and 100 blood donor controls. Results were analyzed comparing area under the ROC curve (ROC-AUC), sensitivity adjusted to 95% specificity (AS95), concordance of sample ZnT8A positive or negative designation, and autoantibody levels.
  
  
  RESULTS
  ZnT8A radio binding assays (RBAs) based on combined immunoprecipitation of the 2 most frequent ZnT8 COOH-terminal domain polymorphic variants showed a median ROC-AUC of 0.848 [interquartile range (IQR) 0.796-0.878] and a median AS95 of 70% (IQR 60%-72%). These RBAs were more sensitive than assays using as antigen either 1 ZnT8 variant only or chimeric constructs joining NH(2)- and COOH-terminal domains, assays based on immunoprecipitation and bioluminescent detection, or assays based on immunofluorescent staining of cells transfected with full-length antigen.
  
  
  CONCLUSIONS
  The DASP workshop identified immunoprecipitation-based ZnT8A assays and antigen constructs that achieved both a high degree of sensitivity and specificity and were suitable for more widespread clinical application.
authors: Genomic Unit for the Diagnosis of Human Pathologies, Center for Translational Genomics and Bioinformatics, San Raffaele Scientific Institute, Milan, Italy. lampasona.vito@hsr.it
authors: Vito
authors: V
authors: Lampasona
authors: Michael
authors: M
authors: Schlosser
authors: Patricia W
authors: PW
authors: Mueller
authors: Alistair J K
authors: AJ
authors: Williams
authors: Janet M
authors: JM
authors: Wenzlau
authors: John C
authors: JC
authors: Hutton
authors: Peter
authors: P
authors: Achenbach
mesh_terms: D000293:Adolescent; D000328:Adult; D001323:Autoantibodies / Q000097:blood*; D027682:Cation Transport Proteins / Q000276:immunology*; D002648:Child; D003922:Diabetes Mellitus, Type 1 / Q000175:diagnosis* / Q000276:immunology; D005260:Female; D006801:Humans; D007118:Immunoassay / Q000592:standards*; D007391:International Cooperation; D059021:Laboratory Proficiency Testing; D008297:Male; D012372:ROC Curve; D012680:Sensitivity and Specificity; D055815:Young Adult; D000075703:Zinc Transporter 8
chemical_list: D001323:Autoantibodies; D027682:Cation Transport Proteins; C492522:SLC30A8 protein, human; D000075703:Zinc Transporter 8