The Endomysial Antibody IgA test is used to diagnose celiac disease, an autoimmune disorder caused by a reaction to gluten, a protein found in wheat, barley, and rye. This test measures the levels of immunoglobulin A (IgA) antibodies against endomysium, a tissue in the lining of the small intestine. When the immune system reacts to gluten, it can damage the endomysium and cause the release of these antibodies. Elevated levels of endomysial antibodies suggest that a person has celiac disease, although a biopsy may be needed to confirm the diagnosis. The Endomysial Antibody IgA test is highly specific for celiac disease and is often used in combination with other tests, such as the tissue transglutaminase antibody (tTG-IgA) test, to aid in the diagnosis.