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Immunology & Autoimmune
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This blood test measures IgA antibodies directed against tissue transglutaminase, an enzyme found in the lining of your small intestine. In people with celiac disease, the immune system reacts to gluten and produces these antibodies, which can damage the intestinal lining and affect nutrient absorption.
The test is most informative when you are regularly eating gluten. Many labs also check your total IgA level, because a low IgA level can make the test less reliable. If IgA is low, your clinician may use IgG-based tests to look for evidence of celiac disease.
Tissue transglutaminase IgA is a key test used to evaluate for celiac disease, a condition in which gluten triggers an immune reaction in the small intestine. Your clinician may order it if you have symptoms such as chronic diarrhea, bloating, abdominal pain, weight loss, iron deficiency, or if you have conditions linked to celiac disease like type 1 diabetes or thyroid disease. It can also be used to monitor response after starting a gluten-free diet.
A positive result increases the likelihood of celiac disease, but diagnosis usually involves a careful review of your symptoms, other blood tests, and sometimes an endoscopy with small bowel biopsies. The test requires a standard blood draw and carries minimal risk, such as minor bruising at the needle site.
Your clinician will interpret the result in the context of your symptoms, diet, and other tests. A negative result while you are eating gluten regularly makes active celiac disease less likely, but it does not completely rule it out, especially if you have low IgA levels or strong clinical suspicion. If symptoms persist, additional tests may be recommended.
A positive result suggests an immune response consistent with celiac disease. Next steps may include endomysial antibody testing, genetic testing, or referral for endoscopy to look directly at the small intestine. If you have already started a gluten-free diet, results can be harder to interpret; do not start or stop gluten without medical advice. For people diagnosed with celiac disease, repeating the test over time can help assess response to a gluten-free diet, alongside symptom tracking and nutritional follow-up.
Reference intervals vary by laboratory, analyzer, methodology, population, and units. The ranges shown here are for education only. Always interpret your results against the reference interval printed on your own lab report.
The test works best when you are regularly eating gluten. Reducing or eliminating gluten before the blood draw can lower antibody levels and make the result less reliable.
Some people have low total IgA, which can lead to falsely low tissue transglutaminase IgA results. Your clinician may check a total IgA level and consider IgG-based tests if IgA is low.
Immunosuppressive drugs, corticosteroids, or therapies that deplete B cells can reduce antibody production and may lower test levels. Recent severe illness can have similar effects.
High-dose biotin supplements can interfere with certain immunoassays. If possible, avoid large biotin doses before testing and tell the lab about any supplements you take.
Autoimmune diseases and liver disorders can sometimes be associated with elevated antibodies, which may complicate interpretation. Your clinician will consider your full medical history.
In very young children, different serologic patterns can occur. Clinicians may add deamidated gliadin peptide tests or use age-appropriate strategies for evaluation.
After starting a gluten-free diet, antibody levels usually decline gradually. Testing too soon after changing your diet may not reflect the full response.
Improper sample handling, hemolysis, or delays in processing can affect immunoassay performance. Using an accredited laboratory helps reduce these pre-analytic issues.
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