title: IgG antibodies against deamidated gliadin peptides for diagnosis of celiac disease in patients with IgA deficiency.
abstract: BACKGROUND
  Assays for IgG antibodies against deamidated gliadin (IgG-anti-dGli) are comparable in performance with tests detecting IgA antibodies against tissue transglutaminase (IgA-anti-tTG) in diagnosing celiac disease (CD). IgA-anti-tTG are absent in IgA deficiency, a condition often associated with CD. In IgA deficiency, IgG-anti-tTG, which have a lower overall diagnostic accuracy, are routinely measured. We examined whether IgG-anti-dGli would be useful for diagnosing CD in patients with IgA deficiency.
  
  
  METHODS
  We studied 34 IgA-deficient CD patients, 185 IgA-competent newly diagnosed children with CD, 316 children without CD, 400 adult blood donors, and 6 control IgA-deficient individuals without CD. Anti-dGli and anti-tTG were measured by ELISA, and endomysium antibodies (EmA) were measured by immunofluorescence on monkey esophagus (IgA as well as IgG class for all antibodies). We calculated diagnostic sensitivity (percentage of patients above cutoff with 95% CIs) according to age-specific cutoffs for 95% diagnostic specificity and according to cutoffs proposed by the manufacturer of the assays.
  
  
  RESULTS
  No IgA-deficient CD patients were positive for any IgA-based antibody assay. Diagnostic sensitivity of IgG-anti-tTG was 91.2% (95% CI 76.3%-97.7%) according to age-specific cutoffs and 82.4% (66.1%-92.0%) according to manufacturer cutoffs. The diagnostic sensitivity of IgG-EmA was 75.8% (58.8%-87.4%) and the sensitivity of IgG-anti-dGli was 88.2% (72.8%-95.9%) according to both cutoffs.
  
  
  CONCLUSIONS
  IgG-anti-dGli and IgG-anti-tTG have comparable diagnostic sensitivities for IgA-deficient celiac patients. IgG-anti-dGli may be useful for diagnosing CD in IgA-deficient patients.
authors.affiliation: Allergy and Immunology Unit, Azienda Ospedaliera San Maria degli Angeli, Pordenone, Italy.
authors.forename: Danilo
authors.initials: D
authors.lastname: Villalta
authors.forename: Elio
authors.initials: E
authors.lastname: Tonutti
authors.forename: Christian
authors.initials: C
authors.lastname: Prause
authors.forename: Sibylle
authors.initials: S
authors.lastname: Koletzko
authors.forename: H Holm
authors.initials: HH
authors.lastname: Uhlig
authors.forename: Pieter
authors.initials: P
authors.lastname: Vermeersch
authors.forename: Xavier
authors.initials: X
authors.lastname: Bossuyt
authors.forename: Martin
authors.initials: M
authors.lastname: Stern
authors.forename: Martin W
authors.initials: MW
authors.lastname: Laass
authors.forename: Julia H
authors.initials: JH
authors.lastname: Ellis
authors.forename: Paul J
authors.initials: PJ
authors.lastname: Ciclitira
authors.forename: Thomas
authors.initials: T
authors.lastname: Richter
authors.forename: Cornelia
authors.initials: C
authors.lastname: Daehnrich
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Schlumberger
authors.forename: Thomas
authors.initials: T
authors.lastname: Mothes
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D002446:Celiac Disease / Q000150:complications / Q000175:diagnosis* / Q000276:immunology; D002648:Child; D002675:Child, Preschool; D005260:Female; D005903:Gliadin / Q000097:blood / Q000276:immunology*; D006801:Humans; D017098:IgA Deficiency / Q000150:complications*; D007074:Immunoglobulin G / Q000097:blood / Q000276:immunology*; D008297:Male; D008875:Middle Aged; D010455:Peptides / Q000097:blood / Q000276:immunology; D012680:Sensitivity and Specificity
chemical_list: D007074:Immunoglobulin G; D010455:Peptides; D005903:Gliadin