Best Tests March 2007
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Choose either EMA or TTG for coeliac disease testing
Coeliac disease (gluten-sensitive enteropathy) is an autoimmune disease of the small intestine which makes people sensitive to dietary gluten. The gluten causes an inflammatory reaction on the lining of the small intestines that interferes with intestinal absorption. It has a prevalence of approximately 1%. The classic symptoms of coeliac disease are steatorrhoea and marked weight loss, but nowadays it is being recognised in people who may present with recurrent diarrhoea, or other vague and non-specific symptoms.
Anti-endomysial (EMA) antibody or anti-tissue transglutaminase (TTG) are the best initial tests for detecting coeliac disease, but small bowel biopsy remains the gold standard for diagnosis. If just one test is offered it will almost certainly be TTG because of the practicalities involved. EMA should however be retained for situations where there is good reason for clinical suspicion (such as deciding whether to proceed to biopsy), in patients who may be on-again/off-again with a gluten free diet (it is less likely to be falsely negative), and for situations where false positive TTGs are suspected.
Although testing for IgA antibodies to tissue transglutaminase or endomysial antibodies has shown excellent sensitivity and specificity for the diagnosis of coeliac disease, there are several provisos for interpreting results:
- People having either EMA and TTG tests must have had adequate gluten (4 slices of bread daily) for six weeks prior to the test. Negative results do not exclude coeliac disease if the patient has a significantly reduced gluten intake.
- IgA deficiency is more common in patients with coeliac disease and the diagnosis may therefore be missed if IgA-based serological tests (EMA or TTG) are used. As a result there should be a lower threshold for performing duodenal biopsy in people with IgA deficiency.
- Hill PG, McMillan SA. Anti-tissue transglutaminase antibodies and their role in the investigation of coeliac disease. Ann Clin Biochem 2006;43:105-117.