Endomysial Antibody Screen, IgA (EMA)
Other marker
Endomysial Antibody IgA
Endomysial Antibody Screen, IgA (EMA)
A highly specific confirmatory test for coeliac disease, reported qualitatively as positive, negative, or equivocal. It detects IgA antibodies against endomysium (connective tissue around muscle fibres) using an immunofluorescence method, and a positive result is very strongly associated with coeliac disease.
PED Notes
Usually ordered as a confirmatory step after a positive tissue transglutaminase IgA, because its specificity for coeliac disease is very high. Like the other IgA-based coeliac tests, it is only valid while eating gluten and is unreliable in people with selective IgA deficiency (check total IgA). For athletes, the same rule applies: do not go gluten-free before the coeliac workup is complete, or the test can turn falsely negative.
When high
When positive:
- A positive endomysial IgA is highly specific for coeliac disease and, combined with a positive tissue transglutaminase IgA, makes the diagnosis very likely
- Confirm with duodenal biopsy in adults while still consuming gluten, and screen for malabsorption consequences (iron, ferritin, vitamin D, B12, folate)
- Proceed to a strict lifelong gluten-free diet only once coeliac disease is confirmed
When equivocal:
- Repeat testing and interpret alongside tTG-IgA, total IgA, and symptoms; an equivocal result on its own is not diagnostic
When low
When negative:
- A negative endomysial IgA in a gluten-consuming person with normal total IgA argues against coeliac disease
- If total IgA is low, the result is unreliable and IgG-based testing (deamidated gliadin IgG) should be used
- Persistent symptoms warrant evaluation for other causes even when coeliac serology is negative
Clinical context:
- The endomysial antibody test is qualitative (positive, negative, or equivocal) and is used to confirm rather than to screen; tissue transglutaminase IgA is the usual first-line quantitative screen
- Its value depends on the person eating gluten and having adequate IgA; always interpret with total IgA
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