Antikörper gegen deamidierten Gliadinpeptid

This group of gliadin antibodies is characterized by a better significance than the older method for the determination of gliadin antibodies. The gluten ingested with food is physiologically only broken down in fragments in the intestine. The remaining gliadin fragments (peptide chains) can be absorbed through the mucosa.

They meet the enzyme transglutaminase. Transglutaminase triggers a structural change in the peptides. They are deamidated at certain protein building blocks (amino acids).

The newer test methods detect antibodies against these deamidated gliadin peptides. These test methods have a higher specificity than the "old" gliadin antibodies. However, they do not replace the previously mentioned autoantibody methods.

The following combinations of antibody test and biopsy (total IgA in the normal range) are conceivable:

• TTG-IgA or EmA-IgA antibodies elevated, biopsy with villous atrophy: celiac disease confirmed.
• TTG-IgA or EmA-IgA antibodies in the normal range, biopsy with villous atrophy: unclear situation, clarify other possibilities for villous atrophy, celiac disease possible
• TTG IgA or EmA IgA antibodies elevated, biopsy WITHOUT villous atrophy: potential celiac disease or error in sample examination or antibody determination. In consultation with the patient / depending on the symptoms, a gluten-free diet should not yet be started, if possible. Further monitoring necessary

In case of IgA deficiency:

TTG-IgA or EmA-IgA antibodies in the norm -> determination of IgG antibodies against tissue transglutaminase or deamidated gliadin peptides (DGP-IgG)

If IgG antibodies are elevated: biopsy. If villous atrophy: celiac disease confirmed, if no villous atrophy: consider other cause or continue gluten-containing diet and follow up.

If IgG antibodies are normal: celiac disease unlikely, consider other cause of symptoms.

In children and adolescents up to 18 years of age, the diagnosis can in many cases be made without performing a small intestine biopsy during a gastrointestinal endoscopy. To do so, all of the following criteria must be met:

• tTG-IgA at least 10 times above the normal limit (example: limit is 7 U/ml, laboratory result is 91 U/ml: the value is thus 13 times above the normal value).
• Collection of a second blood sample and determination of the autoantibodies endomysium (EMA-IgA)

If EMA-IgA is also positive: start of gluten-free diet, celiac disease confirmed.