What Is a Tissue Transglutaminase IgA Test?

Medically Reviewed by Dany Paul Baby, MD on April 20, 2022
5 min read

A tissue transglutaminase IgA test or tTg-IgA test is an effective method used in the diagnosis of celiac disease. It is a blood test that checks for antibodies or immunoglobulins, which are proteins produced by the immune system. A high number of antibodies in blood indicate celiac disease.  

Celiac disease is a long-term or chronic autoimmune disorder that affects your digestive system. An autoimmune disorder is diagnosed when your immune cells start attacking your body. 

Celiac disease is triggered when you eat foods that contain gluten — a protein found in cereals like wheat, barley, and rye and foods like cakes, bread, and pasta. If you have celiac disease, your immune cells react to gluten and attack it. This, unfortunately, can damage your small intestine. 

Celiac disease is different from gluten sensitivity or wheat intolerance. It is a serious condition and can cause long-term digestive problems, which can prevent you from getting enough nutrients.

People who eat too much gluten in their early childhood have a higher risk of developing celiac disease. Research also shows that people who get certain digestive tract infections early in life may develop celiac disease.

The condition can be hereditary, too. If a family member has it, you may have it, too.

Additionally, health conditions like type 1 diabetes and thyroid disease can increase the risk of celiac disease.

Celiac disease symptoms can vary from person to person. If you have celiac disease, you may have the following digestive problems: 

  • Bloating
  • Diarrhea
  • Constipation
  • Gas
  • Vomiting and nausea
  • Stomach or abdominal pain
  • Lactose intolerance, (the inability to digest the sugar in milk due to small intestine damage)
  • Loose and bad-smelling stools 

Symptoms are more common in children than in adults. Celiac disease also causes skin rashes and oral problems like tooth enamel defects or canker sores. Children with celiac disease may have growth problems because their bodies can’t absorb enough nutrients. This can lead to delayed puberty, weight loss, slow development, short height, and mood changes.

Celiac disease testing involves the following:

  • Medical and family history. Celiac disease can be genetic, which means your family members can pass it down to you. Your doctor will ask about your symptoms and check your medical history. They will also check your family history to see if anyone in your family has celiac disease.
  • Physical exam. Your doctor will check your symptoms and look for signs like weight loss, growth problems, pain, or swelling. They may also check for skin rashes and teeth and mouth symptoms to diagnose celiac disease.
  • Blood tests. Your doctor may take a blood sample and check for antibodies. Levels of certain celiac disease antibodies like the tissue transglutaminase antibodies can be detected in the blood.
  • Biopsy. A biopsy involves removing a tissue sample from a part of your body for testing. It is done using an endoscope, which is a tube with a camera attached to it. Your doctor may remove some tissue from your small intestine or skin. They’ll examine it under a microscope, looking for signs of celiac disease.
  • Genetic testing. This testing is done to check if any of your family members with celiac disease have passed it on to you. Your doctor will take your blood sample or collect cells from the inside of your cheek using a swab test. This sample will be tested for genes related to celiac disease.

A tissue transglutaminase IgA (or, tTg-IgA) test helps doctors diagnose celiac disease. If you have celiac disease, your immune system is triggered when you eat gluten. Your body starts treating gluten as a threat. 

Your immune system starts making antibodies or immunoglobulins to fight against the gluten. These antibodies may mistakenly attack an enzyme or protein in your intestines called tissue transglutaminase, which normally repairs and heals cells. That’s why these antibodies are also called anti-tissue transglutaminase antibodies.

When you have celiac disease, the levels of anti-tissue transglutaminase antibodies increase in your body. Doctors check for these antibodies in your blood using the tissue transglutaminase IgA test. 

The tissue transglutaminase IgA test is the most sensitive and effective method of celiac disease testing. It shows positive results in almost 98% of people with celiac disease who eat gluten.

Your doctor will order a tTG-IgA test if you show symptoms of celiac disease. They may also order one if you have conditions like type 1 diabetes or thyroid disease, which increase the risk of celiac disease. You may also have to be tested if any of your family members have celiac disease.

Before undergoing celiac disease testing, you’ll have to eat a gluten-containing diet until the test for accurate results. Even if you have celiac disease, a lack of gluten can skew test results. Doctors recommend getting a tTg-IgA test before you stop eating gluten. No other preparation is required before the test. However, inform your doctor about other medicines you are taking. 

The tissue transglutaminase IgA test is done by taking a blood sample. Your doctor will use a needle to draw blood from your vein. They will then test the blood for anti-tissue transglutaminase antibodies. If your blood has high levels of celiac disease antibodies, you’ll be diagnosed with the condition. 

The tissue transglutaminase IgA test doesn’t have any major risks. It is a simple blood test. However, you may feel a sting or pain when the doctor inserts the needle. You may have bleeding, bruising, or soreness around the site of the needle prick.

The tTg-IgA test may not be accurate in children and people with low anti-tissue transglutaminase antibody levels. This can lead to false-negative results. Your doctor may thus order other diagnostic tests to confirm whether you have celiac disease. 

Test results may also differ based on your age, gender, medical history, and the test used. Consult your doctor for more information regarding tests for celiac disease.