Anti-tissue transglutaminase IgA (tTG-IgA)
Immune system healthAnti-tissue transglutaminase IgA (tTG-IgA) is an antibody that your immune system makes against an enzyme in your gut lining when you have coeliac disease.
Also known as: tTG-IgA, anti-tTG IgA, tissue transglutaminase antibodies, celiac antibody test
It is the recommended first blood test for coeliac disease in adults and is very reliable as long as you are eating gluten and your total IgA is normal. Coeliac disease affects about 1 in 100 people in Europe, and many do not know they have it, because it often shows up indirectly: iron deficiency that keeps coming back, slightly raised liver values, bloating, diarrhoea or tiredness. A positive result is not a diagnosis on its own. A gastroenterologist confirms it, usually with a gastroscopy and a small tissue sample from the small intestine. Do not start a gluten-free diet before this has been clarified, as it can make the test falsely normal.
Why this matters
Celiac disease affects roughly 1 in 100 people in Europe, but the majority remain undiagnosed because symptoms can be subtle or absent. Beyond the classic digestive complaints (bloating, diarrhea, abdominal pain), untreated celiac disease can silently cause iron deficiency, osteoporosis, fatigue, skin rashes (dermatitis herpetiformis), and even neurological symptoms. Screening with tTG-IgA catches the disease early, allowing a gluten-free diet to prevent long-term damage to the gut and other organs. A positive result should be followed up with specialist evaluation.
How this connects to other biomarkers
- A positive tTG-IgA result is only reliable if total IgA is normal. Low total IgA can produce a false-negative, in which case tTG-IgG should be checked instead. In celiac disease, you may also see low Ferritin and low Iron (due to malabsorption), low Vitamin D, low Vitamin B12, and low Folate. Persistently elevated tTG-IgA despite a gluten-free diet suggests ongoing gluten exposure or an alternative diagnosis.
How often should I test Anti-tissue transglutaminase IgA (tTG-IgA)?
One test is usually enough if you have no symptoms and the result is normal. Repeat it if digestive symptoms, unexplained iron deficiency or raised liver values appear later. If a close relative has coeliac disease, ask your doctor how often to retest. After a diagnosis, tTG-IgA shows whether a gluten-free diet is working.
At baseline / for screening: Once, if you have digestive symptoms, unexplained iron deficiency, raised liver values or a close relative with coeliac disease.
When monitoring an intervention or change: After a diagnosis, within the first year of a gluten-free diet and then about once a year, to check the diet is working.
Note: Keep eating gluten as usual until your blood draw. If you have already cut out gluten, the result can be falsely normal, so speak to your doctor about whether to reintroduce it before testing.
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