Celiac Serology: Tests & Interpretation

Instructor: Amy Albert

Amy is a Physician Assistant and certified professional coder. She holds a masters degree and has taught at the graduate school level.

Celiac disease is an autoimmune disease caused by an allergy to gluten. In Celiac disease, the body makes antibodies against gluten causing systemic symptoms. Antibody tests and intestinal biopsies are used to diagnose the disease.

I Can't Eat Gluten!

We all have the friend who is 'gluten intolerant', The one who states that they can not eat pizza because they will get bloated and have diarrhea. Or the friend who says that eating pasta makes them tired and groggy. True gluten intolerance is called Celiac disease. Celiac disease is an autoimmune disease caused by the production of antibodies against the small intestine when gluten is consumed. These antibodies cause inflammation in the small intestine which can result in diarrhea, abdominal bloating, and constipation in children. Depression, weight loss and malabsorption is commonly seen in adults.

Gluten is a protein found in grains such as wheat, barley, and rye. Most foods in the American diet contain some form of gluten, so avoidance is difficult. So what do you tell your friend who wants to be tested for Celiac disease? Fortunately, there are several blood antibody tests available to help diagnose the condition.

What is an Antibody ?

An antibody is a blood protein produced in response to a specific antigen. Antigens are foreign substances that come in contact with your body. Common antigens are viruses, pollen, and bacteria. In Celiac disease, the antigen is gluten, and the body is not happy that gluten is present. In response to the antigen gluten, the body forms several IgA antibodies designed to attack the gluten. IgA antibodies are produced by the immune system to protect mucous membranes, such as the lining of the stomach and intestine. Unfortunately, the antibodies create more harm than good, causing widespread inflammation in the small intestine.

Antibody tests for Celiac Disease

It should come as no surprise that tests for Celiac disease center around the antibody response to gluten. Gluten causes the immune system to produce antibodies called anti-tissue transglutaminase, gliadin peptide, and endomysial antibodies. The most sensitive test for diagnosing celiac disease is the anti-tissue transglutaminase (tTG)-IgA test. According to the Celiac Disease Foundation, 95% of people with celiac disease will have this antibody. If the tTG test is negative, there are two other antibody tests that can be use to diagnose celiac disease. These are called the endomysial antibodies (EMA) and deamidated gliadin peptide antibodies (DGP) tests. These tests are expensive and not as specific as tTG, which is why they are not used for first line screening of Celiac disease.

Is That All?

Since a very small percentage of the population may have elevated Celiac antibodies without having the disease, and a very small percentage of those with Celiac disease can have negative antibody results, the definitive diagnosis for Celiac disease is an intestinal biopsy. If tTG, EMA, or the DGP test is positive, then the definitive diagnosis is to sample a piece of the small intestine. This is done under anesthesia and isn't as painful as it sounds. The small intestinal biopsy shows a characteristic inflammation and erythema, or redness, in someone with Celiac disease.

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