title: Tissue transglutaminase antibodies in celiac disease: assessment of a commercial kit.
abstract: OBJECTIVE
  Tissue transglutaminase was identified as the autoantigen eliciting endomysial antibody. A homemade enzyme-linked immunosorbent assay (ELISA)-based test was recently developed to determine quantitative titers of IgA antitissue transglutaminase antibody. Our objective in this study was to assess the suitability of a newly developed commercial kit for quantitative determination of antibody in patients with untreated celiac disease.
  
  
  METHODS
  We tested serum samples from 79 untreated celiac patients, 42 healthy blood donors, and 18 patients with nonceliac intestinal disorders evaluated in two different centers. Samples were tested for antitissue transglutaminase, and antiendomysial and antigliadin antibodies in the center where diagnosis was performed. To assess interlaboratory variability of methods, 24 samples randomly selected were blindly tested in both centers. Antitissue transglutaminase antibodies were determined using a commercial kit (INOVA Diagnostics, Inc., San Diego, CA).
  
  
  RESULTS
  Untreated celiac patients had significantly higher titers of antitissue transglutaminase than healthy and disease controls (p < 0.00001). According to the cut-off provided by the manufacturers (20 AU/mL), overall sensitivity was 92% (85% for one center and 100% for the other) and specificity was 98% (100% and 95%, respectively). Antiendomysial antibody was 86% sensitive and 100% specific. Discordance between antitissue transglutaminase and antiendomysial antibodies was detected in 13% of patients. Although two antitissue transglutaminase-negative cases had a positive antiendomysial antibody, the inverse situation was found in eight cases. A blind determination of antitissue transglutaminase on the same samples evidenced a good agreement (kappa statistic: 0.66) between both centers when assessment was qualitative (based on the decision of positive or negative). Although correlation of titers for both determinations was highly significant (r: 0.902, p < 0.00001), a very wide interlaboratory variability (median: 50%) was detected when absolute values were considered.
  
  
  CONCLUSIONS
  The quantitative determination of antitissue transglutaminase using a commercial kit was highly sensitive and specific for detection of celiac disease. We observed an incomplete overlapping with antiendomysial antibody. The very high variability of values between laboratories still remains to be solved so as to propose the commercial ELISA assay for the screening of celiac disease.
authors.affiliation: Clinical Department, Gastroenterology Hospital, Universidad del Salvador, Buenos Aires, Argentina.
authors.forename: E
authors.initials: E
authors.lastname: Sugai
authors.forename: G
authors.initials: G
authors.lastname: Selvaggio
authors.forename: H
authors.initials: H
authors.lastname: Vazquez
authors.forename: M
authors.initials: M
authors.lastname: Viola
authors.forename: R
authors.initials: R
authors.lastname: Mazure
authors.forename: B
authors.initials: B
authors.lastname: Pizarro
authors.forename: E
authors.initials: E
authors.lastname: Smecuol
authors.forename: D
authors.initials: D
authors.lastname: Flores
authors.forename: S
authors.initials: S
authors.lastname: Pedreira
authors.forename: E
authors.initials: E
authors.lastname: Mauriño
authors.forename: J C
authors.initials: JC
authors.lastname: Gomez
authors.forename: J C
authors.initials: JC
authors.lastname: Bai
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000888:Antibodies, Anti-Idiotypic / Q000032:analysis; D001323:Autoantibodies / Q000032:analysis*; D015415:Biomarkers / Q000097:blood; D001706:Biopsy; D002446:Celiac Disease / Q000097:blood / Q000201:enzymology* / Q000473:pathology; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D019204:GTP-Binding Proteins / Q000097:blood / Q000276:immunology*; D005903:Gliadin / Q000097:blood / Q000276:immunology; D006801:Humans; D007070:Immunoglobulin A / Q000276:immunology; D007074:Immunoglobulin G / Q000276:immunology; D008297:Male; D008875:Middle Aged; D000091345:Protein Glutamine gamma Glutamyltransferase 2; D011503:Transglutaminases / Q000276:immunology*
chemical_list: D000888:Antibodies, Anti-Idiotypic; D001323:Autoantibodies; D015415:Biomarkers; D007070:Immunoglobulin A; D007074:Immunoglobulin G; D005903:Gliadin; D000091345:Protein Glutamine gamma Glutamyltransferase 2; D011503:Transglutaminases; D019204:GTP-Binding Proteins