Finding the right tests…
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Finding the right tests…
ELISA
Tissue transglutaminase IgA, or tTG-IgA, is the blood test doctors reach for first when celiac disease is suspected - an autoimmune reaction to gluten that damages the lining of the small intestine. It checks for an antibody your immune system makes against an enzyme called tissue transglutaminase, and it only works accurately if you're still eating gluten regularly at the time of the blood draw. Because about 2 to 3 out of every 100 people with celiac disease also have a separate condition called IgA deficiency, which can make this specific test falsely negative, labs usually check your total IgA level alongside it.
The result is typically reported as positive or negative against the lab's cutoff, sometimes with a numeric antibody level. Studies show the test correctly identifies roughly 78 to 100 out of 100 people who truly have celiac disease, and correctly clears roughly 90 to 100 out of 100 people who don't - though performance depends on the specific assay a lab uses. A positive result doesn't confirm celiac disease outright; it typically leads to a small intestine biopsy, which remains the step that actually confirms the diagnosis.
This test looks for antibodies your immune system makes in response to gluten. If you've cut gluten from your diet before the blood draw, the antibody level can drop enough to cause a false-negative, which is why doctors advise against a gluten-free diet before celiac testing is complete.
Roughly 2 to 3 out of every 100 people with celiac disease also have IgA deficiency, where the body makes very little IgA of any kind. In someone with this deficiency, a tTG-IgA test can come back falsely negative simply because there isn't enough IgA to detect. Checking total IgA at the same time flags this, and if it's low, doctors switch to an IgG-based version of the same test.
- A referral for an upper endoscopy, where a doctor takes small tissue samples from the small intestine - Examining those samples under a microscope for the pattern of damage seen in celiac disease - Continuing to eat gluten until the biopsy is done, for the same accuracy reasons as the blood test
A positive tTG-IgA result is strongly suggestive but not proof by itself - other conditions can occasionally raise this antibody without celiac disease being present. The intestinal biopsy is what most professional guidelines still treat as the step that confirms an adult diagnosis.
Yes, you need to be eating gluten regularly at the time of the blood draw, since stopping beforehand can lower antibody levels enough to cause a false-negative result. Don't start a gluten-free diet on your own before celiac testing is complete.
About 2 to 3 out of every 100 people with celiac disease also have IgA deficiency, which can make the tTG-IgA test falsely negative. Checking total IgA at the same time catches this, so an alternative IgG-based test can be used instead if needed.
Not on its own. It's strongly suggestive, but confirming celiac disease usually needs a small intestine biopsy taken during an upper endoscopy.
This page is general information about the test, not medical advice. Your own report's reference ranges apply — please discuss your results with your doctor.
Most labs report results as positive or negative against their own cutoff, sometimes alongside a numeric value. Ranges and cutoffs vary by lab, so check the reference value printed on your own report.
There's no fixed fasting rule for this test specifically. Ask your doctor or the centre when you book, especially if other blood work is being done at the same visit.
Yes, tTG-IgA is used in children as well as adults, provided they are old enough to reliably produce IgA antibodies and are still eating gluten. Ask your doctor about age-specific considerations for younger children.