Gliadin (Deamidated) Antibodies, IgG and IgA

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Subject: Gliadin (Deamidated) Antibodies, IgG and IgA

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Definition

  • ELISA-based deamidated gliadin (DGP) antibody assay is a more useful test in the diagnosis of celiac disease than the native gliadin antibody assays. DGP assays seem to be equivalent to, but not better than, tissue transglutaminase–IgA (TTG-IgA); however, DGP assays may have additive benefits in celiac screening because the combination of the two tests can increase the sensitivity without actually lowering the specificity. The DGP test also may be beneficial in circumstances when the TTG results are indeterminate. In addition, among young children, it seems to appear before TTG and to resolve faster in the context of gluten withdrawal.

  • Other names: DGP, gliadin IgA, and IgG.

  • Normal range:

    • Negative: ≤19 U

    • Weak positive: 20–30 U

    • Positive: ≥31 U

Use

  • For initial evaluation for celiac disease in IgA-deficient population

  • Monitoring response to dietary therapy

  • When TTG-IgA is normal in patients with villous atrophy

  • Patients with a high pretest probability of celiac disease but a negative TTG-IgA: guiding a decision regarding the need for endoscopy and biopsy

Interpretation

Increased In

  • Celiac disease

  • Dermatitis herpetiformis

Limitations

  • Biopsy of the proximal small intestine is indicated to confirm the diagnosis of celiac disease in a patient with positive serologic test(s) for antibodies to TTG or deamidated gliadin. It is recommended that multiple tissue specimens be taken at biopsy to avoid false-negative histology in patients with focal disease.

  • The levels of antibodies to TTG and deamidated gliadin peptides decline slowly in patients treated with a gluten-free diet, and serologic testing may be repeated to assess the response to treatment. In a typical patient, it may take up to 1 year for results to normalize. Persistently elevated results suggest poor adherence to the gluten-free diet.

 
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