Gewebstransglutaminase-Antiköper

Autoantibody of the IgA or IgA type directed against the body's own tissue transglutaminase. In principle, the tissue transglutaminase antibody test detects the same antibody as the endomysium antibody test, but with a different test procedure (ELISA test procedure). The antigen , the transglutaminases (more precisely: protein-glutamine-γ-glutamyltransferases) are enzymes that can produce cross-links within or between proteins, greatly altering the properties of the substrate. An example is the solidification of fibrin in blood clotting by factor XIII.

The test for tissue transglutaminase antibodies (tTG-IgA antibodies) is most frequently performed as the first test, also because it is an ELISA procedure. In contrast to the endomysium immunofluorescence test (immunofluorescence test on tissue sections), this is much less time-consuming. In the German celiac disease guideline of 2014, the test for tissue transglutaminase antibodies and the test for endomysium antibodies are considered equivalent.

All antibody tests distinguish between IgA and IgG antibodies. EmA IgA and tTG IgA antibodies are the most reliable in showing whether or not celiac disease is present. A negative antibody test can exclude the presence of celiac disease/sprue with a relatively high degree of certainty.

It is important to exclude IgA deficiency by simultaneously determining immunoglobulin A (total IgA ). Approximately 3-7% of all coeliac disease patients are unable to produce antibodies of this type. In the case of IgA deficiency, the IgA antibody tests against tissue transglutaminase or endomysium cannot be used, as they usually give a negative result even in the case of a full-blown celiac disease/sprue.

In this case, IgG antibodies against transglutaminase and against deamidated gliadin peptides should be determined.

It is important to bear in mind during the diagnostic process that antibodies which are elevated under a gluten-containing diet drop into the normal range as a result of the gluten-free diet and are therefore no longer detectable. Antibody tests carried out under a very low gluten to gluten-free diet therefore do not allow a statement to be made as to whether or not celiac disease is present. However, antibody tests can be used to monitor the course of the disease, as normalised titres in the absence of symptoms usually indicate good dietary compliance.

If celiac disease/sprue is suspected, the diagnosis should be confirmed by an endoscopic biopsy from the duodenum. The mucosal changes also regress under diet, so that a usable sample can only be obtained with sufficient gluten intake.