Tissue Transglutaminase IgA (tTG-IgA)
The tissue transglutaminase IgA (tTG-IgA) test detects IgA antibodies against an enzyme in your gut. It is the main blood test used to screen for celiac disease.
Because tTG-IgA is the preferred first-line screen for celiac disease, an immune reaction to gluten that can damage the small intestine. It helps a clinician decide whether further evaluation, such as a biopsy, is warranted. For the test to be accurate, you generally need to be eating gluten, and your total IgA level is often checked too.
An elevated tTG-IgA suggests celiac disease may be present and typically prompts further evaluation, often including a small-intestine biopsy for confirmation. Because a positive screen is not a final diagnosis, your clinician confirms the result before you make lasting changes like a gluten-free diet.
A negative tTG-IgA makes celiac disease less likely, especially if you have been eating gluten and your total IgA is normal. Because IgA deficiency can cause a falsely negative result, your clinician may check total IgA or use alternative tests when suspicion remains.
A negative result is typical, provided you have been eating gluten and your total IgA is normal. Any positive result should be confirmed and interpreted by your clinician before dietary changes.
Sources
Educational context only, not medical advice or a diagnosis. Reference ranges vary by lab, age and sex; always discuss your results with a clinician.