tTG-IgA

Also written as: tissue transglutaminase IgA, celiac test, tTG antibodies

The main blood screening test for celiac disease, an immune reaction triggered by eating gluten.

What it measures

IgA-class antibodies against tissue transglutaminase, an enzyme found in the lining of the gut. In celiac disease the immune system attacks this enzyme when gluten is eaten, and the test measures the level of those antibodies in the blood.

Why a doctor orders it

The usual first blood test when celiac disease is being considered, prompted by things like long-standing digestive symptoms, unexplained anemia, or a family history of celiac disease. It is often ordered with a total IgA level, because naturally low total IgA can make this test falsely reassuring.

What is generally associated with a higher result

Broadly associated with celiac disease in people who are eating gluten at the time of testing. Mild elevations are occasionally seen in other conditions affecting the gut or liver, which is one reason confirmation is usually sought before any conclusion is drawn.

What is generally associated with a lower result

A negative result is generally the expected finding. It is less informative in people with low total IgA and in people who were eating little or no gluten before the test.

Everyday things that move this number

Not every shift in a value reflects disease. These are ordinary factors known to affect this particular measurement:

A gluten-free or low-gluten diet before the blood draw, which can produce misleadingly negative results
Naturally low total IgA levels, which some people have without knowing it
Age - very young children may not yet make detectable antibodies
The laboratory method used, since units and assays differ between labs

Questions to take to your appointment

Was I eating enough gluten before the test for the result to be reliable?
Was a total IgA level checked alongside this?
If this is positive, what would the next confirmatory step be, such as a biopsy?
Should close family members consider being screened?

Build a printable questionnaire with your own results →

Where to read more

MedlinePlus, from the US National Library of Medicine, publishes patient-facing pages on individual lab tests and is a reliable next stop: medlineplus.gov/lab-tests .

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