IgA: What This Antibody Means for Celiac Screening

IgA is a blood antibody protein that helps us fight off infections. Our body makes many different types of IgA proteins in response to infections. In celiac disease, which is an autoimmune condition, our body responds to intake of gluten-containing foods by making specific IgA proteins that damage the small intestine.

The blood test for celiac disease looks for a certain type of IgA antibody called anti-TTG. If your body is making normal levels of IgA, the anti-TTG IgA test is very effective at identifying celiac disease. However, people with a rare condition called IgA deficiency, are at risk of having a false negative anti-TTG IgA test, even if they have celiac disease. For this reason, we check IgA levels as part of the celiac blood test. If your IgA levels are low, then we recommend a different test for celiac disease that does not depend on IgA.

anti-TTG IgA should be measured concurrently with an IgA level to rule out IgA deficiency, which can result in a false negative anti-TTG IgA titre. Our lab testing partner's reference range for IgA is: 0.80 g/L is low, 0.80–4.90 g/L is normal, and greater than 4.90 g/L is high.

Note: The celiac screen test is most accurate when you have a diet that includes gluten. People who take the test while on a gluten-free diet may have a false negative result. If you were on a gluten-free diet when you took this blood test, additional testing may be recommended.