Tissue Transglutaminase Ab IgA (tTG-IgA)

What is Tissue Transglutaminase Ab IgA (tTG-IgA)?

Measures IgA antibodies to tissue transglutaminase, the main blood test to screen for celiac disease on a gluten-containing diet.

Tissue transglutaminase IgA (tTG-IgA) antibodies form when the immune system reacts abnormally to gluten, a protein found in wheat, barley, and rye, and mistakenly targets the enzyme tissue transglutaminase. This test relates to the immune system and digestive tract, since celiac disease damages the lining of the small intestine over time. Clinicians commonly order tTG-IgA as the first-line screening test in people with digestive symptoms, unexplained nutrient deficiencies, or a family history of celiac disease, and it is generally most accurate while the person continues eating gluten. Because some people have low total IgA levels, which can cause falsely low tTG-IgA results, a total IgA level is often checked at the same time. A positive tTG-IgA result is typically followed by further evaluation, sometimes including a small intestine biopsy, to help confirm the diagnosis.

Lifestyle factors that influence this marker

• Continue eating a balanced diet that includes gluten unless advised otherwise, since reducing gluten before testing can affect accuracy
• Maintain adequate intake of fiber, fruits, and vegetables to support digestive health
• Stay well hydrated
• Prioritize regular meals to support consistent digestion
• Support overall gut health through diverse, whole-food choices
• Avoid smoking, which has been linked with broader digestive tract irritation

Tests often checked alongside this

• Tissue Transglutaminase IgG (tTG-IgG) — checked when IgA deficiency is suspected
• Total IgA — helps confirm whether the tTG-IgA result is reliable
• Deamidated Gliadin Peptide (DGP) Antibody — sometimes used as an additional celiac marker
• Complete blood count — can reveal anemia associated with malabsorption

How this can show up in how you look and feel

• May be associated with digestive symptoms such as bloating, diarrhea, or abdominal discomfort
• May be associated with unexplained fatigue or nutrient deficiencies
• May be associated with unintended weight changes in some individuals
• May be associated with skin changes such as an itchy rash in some cases

What can affect this marker

• Age
• Diet (gluten intake at time of testing)
• Inflammation
• Lab variability between testing methods

What to track over time

• Whether antibody levels decline over time on a gluten-free diet, if one is followed
• How this result fits with total IgA and biopsy findings, if performed
• Repeat testing may be considered periodically if a gluten-free diet is undertaken to monitor response

What to ask your doctor

• Should my total IgA level be checked alongside this result?
• Do I need further evaluation, such as a biopsy, based on this result?
• Was I eating enough gluten before this test for it to be accurate?
• How should this result guide any dietary changes going forward?

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