Tissue Transglutaminase IgA (TTG-IgA)
Tissue transglutaminase IgA antibody is the first-line screening test for celiac disease — an autoimmune reaction to dietary gluten causing small bowel damage, malabsorption, anemia, osteoporosis, and a wide range of systemic symptoms. TTG-IgA has high sensitivity (>90%) and specificity (>95%) for celiac disease in the right clinical setting. Critically, it must be tested while the patient is still eating gluten — a gluten-free diet normalizes the test and can mask the diagnosis.
Reference Ranges
Male
0 – 15
U/mL
Female
0 – 15
U/mL
Child
0 – 15
U/mL
Reference ranges may vary by laboratory. Always compare with the range printed on your lab report.
What Low Levels Mean
A negative TTG-IgA in a patient eating gluten makes celiac disease unlikely. Important caveat: celiac disease is strongly associated with selective IgA deficiency (affects ~2% of celiac patients). If clinical suspicion is strong and TTG-IgA is negative, check total serum IgA — if IgA is low, TTG-IgG or deamidated gliadin IgG should be used instead.
What High Levels Mean
Positive TTG-IgA strongly suggests celiac disease. Titres >10× upper limit of normal are often considered diagnostic without biopsy in children; in adults, small-bowel biopsy remains the gold standard to confirm and characterize damage. Once diagnosed, lifelong gluten-free diet is the only effective treatment and leads to symptom resolution, mucosal healing, and normalization of antibody levels over 6–12 months.
Frequently Asked Questions
Do I need to keep eating gluten before the test?
Yes. TTG antibodies drop quickly on a gluten-free diet, and the test can turn falsely negative within weeks. Eat gluten (at least 1–2 servings of wheat-containing food daily) for a minimum of 4–6 weeks before testing. Stopping gluten 'just to be safe' before testing is the most common cause of missed celiac diagnoses.
What if I have IgA deficiency?
Selective IgA deficiency is common in celiac patients (~2%) and causes false-negative TTG-IgA. When celiac is suspected, check both TTG-IgA and total IgA. If total IgA is low, order TTG-IgG or deamidated gliadin peptide IgG instead. Missing this step is a common pitfall in celiac diagnosis.
What happens after a positive TTG-IgA?
Referral to a gastroenterologist for duodenal biopsy (usually 4–6 samples from distal duodenum plus 1–2 from duodenal bulb) — villous atrophy, crypt hyperplasia, and increased intraepithelial lymphocytes confirm celiac disease. In children with very high TTG titres (>10× ULN), biopsy may sometimes be avoided under specific ESPGHAN criteria. Lifelong gluten-free diet follows and TTG is rechecked after 6–12 months to confirm response.
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This information is for educational purposes only and should not replace professional medical advice. Always consult your doctor for interpretation of your test results.
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