A significant percentage of patients who have the diarrhea problems of celiac sprue have IgA (most specific &  sensitive Ab test for celiac sprue, at least 90% for each) anti-endomysial (anti-EMA) antibodies circulating in their blood. Endomysial antibodies (EMA) are directed toward the morphological sheath around the smooth and striated muscle bundles of the middle third of the esophagus and were discovered in 1978. This is an IFA-type test. When the clinical suspicion for celiac disease is not very high, the presence of this antibody (or the anti-gliadin IFA-type antibody) may serve as an indication for capsule or endoscopic duodenal/small bowel biopsy to help make or refute the diagnosis of celiac disease [about the disease, GSE]. Monkey esophagus (good for EMA, ASMA, and anti-skin) is the classical substrate (honeycomb pattern is positive), but the EMA antigens are found in human, rat, and others and in such as stomach, jejunum, and umbilical cord.

Anti-reticulin antibody was an original GSE-associated antibody, followed by anti-gliadin and then anti-EMA. There is also a newer test in an EIA/ELISA format called the tTG test which detects anti-endomysial  IgA Ab because that Ab (same as the IFA Ab)  has affinity for the tTG (tissue transglutaminase) cross-linking enzyme (the specific antigen in the EMA-positive perimuscular sheath), especially when it is complexed to gliadin as a test substrate (antibodies to gliadin-tTG complex).

In the USA, the prevalence of these antibodies among Caucasian blood donors is 0.3-0.4% (whereas the prevalence of GSE cases among USA Caucasians is 0.3-1.0%...that is, every person with GSE may not yet be anti-tTG positive). False negative serology in cases with H&E-normal villi is about 20% for anti-EMA and 50% for anti-gliadin; false positive rate for cases ultimately proven to be GSE negative is 5% for anti-EMA and 20% for anti-gliadin³.

We started offering this test in our lab in early 2008: results of 0-20 are "negative"; 21-30 are "weakly reactive"; and, greater than 30 are "moderately to strongly reactive". In early May of 2010 (following a test result of 25 that that failed to positively correlate with the prior normal CD3-amplified villous tip score on the patient's duodenal biopsies[CP10-11], we adjusted our reporting so that less than 20 units is "negative"; 20-30 units are "indeterminate"; and cases with greater than 30 units are "positive"⁵.

As with other tests on IFA substrates, one might stumble upon some other unsuspected antibody such as ASMA [CN09-87].

Situations having undetectable antibodies:

• earliest stage of disease (may not even be diagnosable disease by biopsy)
• small intestinal lymphoma
• refractory sprue (previous biopsy-proven celiac sprue but with failure to become well on a gluten-free diet)
• IgA-deficient individuals (one in 500 persons in USA) won't have the appropriate IgA Ab positivity and yet have celiac disease
• about 20% of early GSE cases (see false negative rates, above³.

Situations having detectible antibodies:

• celiac sprue cases, active and untreated
• 5% false positive anti-EMA rate in cases clinically suspect for celiac disease (GSE) but subsequently proven not GSE³.
• this antibody decreases/disappears with treatment and is very good for checking on dietary compliance and treatment success

Synonyms: tTG test, anti-EMA

References:

1. Sleisinger and Fordtran's: Gastrointestinal and Liver Diseases, 6th Ed., vol. 2, 1998.
2. James Goeken, MD, CAP Today, August 2000, page 66
3. Goldstein, NS and Underhill, J, Morphologic Features Suggestive of Gluten Sensitivity in Architecturally Normal Duodenal Biopsy Specimens,  AJCP 116(1):63-71, July 2001.
4. Carter JB, NewsPath, March 2008 (celiac serology review).
5. Carter JB, 5 May 2010 LML lab director's memo.