title: A comparative study of tissue transglutaminase antibodies and endomysium antibody immunofluorescence in routine clinical laboratory practice.
abstract: BACKGROUND
  The demand for screening for coeliac disease has grown rapidly over the last few years. Laboratories depending on immunofluorescence assays are faced with an increasing workload using a labour-intensive test, and an alternative to this test has been sought. This study compares tissue transglutaminase (TTG) and endomysium antibodies (EMA) in a routine clinical laboratory situation.
  
  
  METHODS
  An immunofluorescence IgA EMA test was compared with a guinea pig TTG antibody ELISA for 816 unselected requests for gut antibody screening. Discrepant results were investigated more fully using a variety of human source TTG antigen kits.
  
  
  RESULTS
  Guinea pig TTG ELISA and EMA assays showed agreement for 93.6% of samples. Four samples were misclassified and 48 samples gave false positive TTG results. Study of 46 EMA samples (this group included 39 of the 'discrepant' negative EMA/positive guinea pig TTG group) using three different human purified and/or recombinant TTG sources showed that 42 patients had no TTG antibodies using human sources, three were misclassified and one patient had negative EMA and positive TTG results that could not be readily explained. Further study of 32 EMA positive samples showed almost complete agreement between the human source TTG kits.
  
  
  CONCLUSIONS
  We can recommend the replacement of EMA with ELISA for TTG antibodies for the routine screening for coeliac disease, but all positive TTG antibodies should still be followed up with IgA EMA and samples should be screened for IgA deficiency.
authors.affiliation: Department of Chemical Pathology, Queen Alexandra Hospital, Portsmouth PO6 3LY, UK. david.sinclair@porthosp.nhs.uk
authors.forename: David
authors.initials: D
authors.lastname: Sinclair
authors.forename: Callum B
authors.initials: CB
authors.lastname: Pearce
authors.forename: Michael S L
authors.initials: MS
authors.lastname: Saas
authors.forename: David
authors.initials: D
authors.lastname: Poller
mesh_terms: D000818:Animals; D002446:Celiac Disease / Q000175:diagnosis*; D004797:Enzyme-Linked Immunosorbent Assay; D005455:Fluorescent Antibody Technique; D019204:GTP-Binding Proteins / Q000032:analysis / Q000276:immunology*; D006801:Humans; D007070:Immunoglobulin A; D000091345:Protein Glutamine gamma Glutamyltransferase 2; D012680:Sensitivity and Specificity; D011503:Transglutaminases / Q000032:analysis / Q000276:immunology*
chemical_list: D007070:Immunoglobulin A; D000091345:Protein Glutamine gamma Glutamyltransferase 2; D011503:Transglutaminases; D019204:GTP-Binding Proteins