Transglutaminase

Blood Test: Tissue Transglutaminase IgA, IgG What It Is

A tissue transglutaminase (tTG) IgA and/or IgG test is used as part of an evaluation for certain autoimmune conditions, most notably celiac disease.

An autoimmune disease can occur when the body's immune system mistakenly perceives a nonthreatening substance. In the case of people with celiac disease, gluten (a protein found in wheat, barley, rye, and oats) is seen as a foreign invader and is attacked by the immune system. This immune system response in celiac disease also involves the production of antibodies directed against an enzyme normally present in the intestines called tissue transglutaminase (tTG).

In celiac disease, the body produces two types of antibodies that attack tTG: immunoglobulin A (IgA) and immunoglobulin G (IgG). Measuring the IgA form of tTG antibody in the blood is more useful in detecting celiac disease because it's made in the small intestine, where gluten causes inflammation and irritation in sensitive people.

Levels of the IgG form of tTG antibody, on the other hand, are less specific to celiac disease, but may still be useful in diagnosing the condition in people who are unable to make normal amounts of IgA antibodies.

Why It's Done

The tTG IgA or IgG antibody tests are usually done to help doctors diagnose celiac disease.

Preparation

For accurate results, your child must currently be eating a diet that includes gluten-containing foods, such as breads, pastas, and baked goods. The body will only produce antibodies when it's exposed to gluten. If gluten has been removed from the diet, there won't be an antibody response to measure.

On the day of the test, having your child wear a T-shirt or short-sleeved shirt can make things easier for your child and the technician who will be drawing the blood.

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