Anti-endomysial antibody (EMA)
A blood antibody test that is highly specific for coeliac disease. When positive, it strongly supports the diagnosis, so it is used mainly to confirm a positive anti-tTG result. Like anti-tTG, it is an IgA-based test, so total IgA is checked alongside it.
What it measures
The anti-endomysial antibody (EMA) is an autoantibody the immune system produces in coeliac disease — an autoimmune reaction to gluten that damages the lining of the small intestine. It targets a component of connective tissue and is detected by a specialised technique that gives a positive-or-negative (titre) result. EMA's defining feature is its very high specificity: a positive EMA is rarely seen in anyone who does not have coeliac disease, so it strongly supports the diagnosis. Because it is more labour-intensive and operator-dependent than the anti-tTG test, it is not usually the first screen. Instead, the typical pathway is to screen with anti-tTG (IgA) and, when that is positive, use EMA to confirm. Both are IgA antibodies, so a total IgA level is measured at the same time — a person who is IgA deficient can give a falsely negative result, in which case IgG-based tests are used. Crucially, all of these antibody tests only work while gluten is still being eaten; a gluten-free diet lowers the antibodies and can produce false negatives. EMA is a confirmatory piece of the coeliac diagnosis, interpreted with anti-tTG and, usually, a small-bowel biopsy.
What a high value can mean
- A positive EMA strongly supports coeliac disease — it is highly specific, so a positive result rarely occurs without the condition.
- Confirmation of a positive anti-tTG — the main way EMA is used.
- It must be interpreted on a gluten-containing diet — a gluten-free diet lowers the antibody.
- It is usually followed by, or read with, a small-bowel biopsy — to confirm the diagnosis.
What a low value can mean
- A negative EMA makes coeliac disease less likely — but does not fully exclude it, especially if gluten has been avoided.
- A false negative with IgA deficiency — why total IgA is checked and IgG-based tests are used if needed.
- A false negative on a gluten-free diet — the test needs gluten in the diet to be valid.
When to discuss with a doctor
Anti-endomysial antibody is a confirmatory test for coeliac disease rather than a first-line screen. It is typically used after a positive anti-tTG, because a positive EMA is highly specific and strongly supports the diagnosis. Two things are essential for a valid result: gluten must still be in the diet (a gluten-free diet lowers the antibodies and can cause false negatives, so testing should not be done after cutting gluten out), and total IgA is checked so that IgA deficiency does not hide a positive result. A positive EMA usually leads to confirming the diagnosis, often with a small-bowel biopsy, and starting a gluten-free diet under guidance, along with checking for nutritional deficiencies. Mediora.AI shows EMA alongside anti-tTG and total IgA so the coeliac serology is read together; the diagnosis and next steps belong with your doctor.