title: Is immunoglobulin A anti-tissue transglutaminase antibody a reliable serological marker of coeliac disease?
abstract: BACKGROUND
  Anti-tissue transglutaminase (tTG) antibody is being used increasingly as a diagnostic tool in the serological investigation of coeliac disease. However, positive predictive values of immunoglobulin A (IgA) anti-tTG for coeliac disease in prospective studies have been disappointing and false-positive results are reported.
  
  
  OBJECTIVE
  To assess the clinical utility of cascade testing for anti-tTG and anti-endomysium antibody (AEA).
  
  
  METHODS
  Two unselected retrospective cohorts from routine diagnostic investigation for possible gluten sensitive enteropathy: group 1 comprised 57 cases seropositive for anti-tTG and group 2 comprised 52 cases seronegative for anti-tTG. In both groups, all cases had also undergone small-intestinal biopsy.
  
  
  METHODS
  Patients were assessed for the presence of IgA anti-tTG by enzyme-linked immunosorbent assay and for IgA AEA by immunofluorescence.
  
  
  RESULTS
  The positive predictive value of IgA anti-tTG for biopsy-confirmed coeliac disease was 54%. The positive predictive value of dual positivity for anti-tTG and AEA was 97%. The negative predictive value of IgA anti-tTG was 100%.
  
  
  CONCLUSIONS
  The data presented here support the use of IgA anti-tTG as an initial screen for coeliac disease. Coeliac disease is unlikely when IgA anti-tTG is absent. However, many false-positive results are seen, and clinical utility and diagnostic efficiency are improved markedly if positive results are confirmed with the more accurate, but labour-intensive, AEA assay.
authors.affiliation: Immunology and Immunogenetics, North Bristol NHS Trust, Southmead Hospital, Bristol, UK.
authors.forename: Robert J
authors.initials: RJ
authors.lastname: Lock
authors.forename: Susan
authors.initials: S
authors.lastname: Stevens
authors.forename: Maxton C L
authors.initials: MC
authors.lastname: Pitcher
authors.forename: David J
authors.initials: DJ
authors.lastname: Unsworth
mesh_terms: D000906:Antibodies / Q000097:blood*; D001323:Autoantibodies / Q000097:blood; D015415:Biomarkers / Q000097:blood; D002446:Celiac Disease / Q000175:diagnosis*; D004797:Enzyme-Linked Immunosorbent Assay / Q000379:methods; D005455:Fluorescent Antibody Technique / Q000379:methods; D019204:GTP-Binding Proteins / Q000276:immunology*; D006801:Humans; D007070:Immunoglobulin A / Q000276:immunology*; D011237:Predictive Value of Tests; D000091345:Protein Glutamine gamma Glutamyltransferase 2; D012189:Retrospective Studies; D012698:Serologic Tests; D011503:Transglutaminases / Q000276:immunology*
chemical_list: D000906:Antibodies; D001323:Autoantibodies; D015415:Biomarkers; D007070:Immunoglobulin A; D000091345:Protein Glutamine gamma Glutamyltransferase 2; D011503:Transglutaminases; D019204:GTP-Binding Proteins