Anti-Endomysial Antibody (EMA)
|Description:||IgA anti-endomysial antibodies remain the most specific test for coeliac disease or dermatitis herpetiformis. IgA anti-tTg antibodies are the same as most IgA anti-endomysial antibodies. They are more sensitive but slightly less specific than anti-endomysial antibodies. Since anti-tTg can be readily automated, this test is used as a screening test.All sera positive for IgA anti-tTg antibodies are assayed for IgA anti-endomysial antibodies. Both assays are far more sensitive and specific than the anti-gliadin antibody tests that used to be used. The endomysium is the term given to the connective tissue surrounding the smooth muscle bundles of many tissues. Anti-endomysial antibodies (directed against non-collagenous extracellular matrix proteins made by fibroblasts) are detected using monkey oesophageal tissue. The antigens are generated by the effect of tissue transglutaminase which modifies glutamine residues in proteins to glutamic acid. The same process occurs in wheat gluten and explains the link between antibodies to gluten and autoantibodies to the gut.|
|Indication:||Confirmatory test for coeliac disease, dermatitis herpetiformis.
See also Coeliac Screen.
|Interpretation:||IgA anti-endomysial antibodies are found in 90% coeliac patients. They are a very specific & sensitive marker for coeliac disease and dermatitis herpetiformis. The anti-endomysial antibody test has been suggested to be 98% sensitive and 98% specific for clinical or subclinical coeliac disease. Since coeliac disease is commonly associated with IgA deficiency, care must be exercised in diagnosing these patients since clearly they do not express IgA antibodies. IgG anti-endomysial antibodies will be assayed.|
|Sample:||Serum Separator Tube (SST)|
|Assay details:||Indirect immunofluorescence using monkey oesophagus.|
|Restrictions:||In general, only performed where anti-tissue transglutaminase is positive.|
|Assay range notes:||Result reported as POSITIVE/NEGATIVE|
|Turnaround time:||5 – 7 days|
|Analysing laboratory:||Immunology JCUH|