Celiac Disease Diagnosis & Tests

How is celiac disease diagnosed?

Celiac disease is suspected when individuals have signs or symptoms of malabsorption or malnutrition. Other diseases, however, can produce malabsorption and malnutrition, for example, pancreatic insufficiency (a pancreas that is not able to produce digestive enzymes), Crohn's disease of the small intestine, and small intestinal overgrowth of bacteria. It is important, therefore, to confirm suspected celiac disease with appropriate testing.

Small intestinal biopsy

Small intestinal biopsy is considered the most accurate test for celiac disease. Small intestinal biopsies can be obtained by performing an esophagogastroduodenoscopy (EGD). During an EGD, the doctor inserts a long, flexible viewing endoscope through the mouth and into the duodenum. A long, flexible biopsy instrument then can be passed through a small channel in the endoscope to obtain samples of the intestinal lining of the duodenum. Multiple samples usually are obtained to increase the accuracy of diagnosis. A pathologist then can examine the biopsies (under a microscope) for loss of villi and other characteristics of celiac disease such as increased numbers of lymphocytes.

Small intestinal biopsy does however, have some limitations. For example, acute viral gastroenteritis and allergy to cow's milk or soy protein can cause abnormal small intestinal biopsies that are indistinguishable from celiac disease. However, acute viral gastroenteritis is not easily confused with celiac disease because of the difference in the acuteness of symptoms. (Acute viral gastroenteritis has a sudden onset of symptoms and last only a few days.) It is however, easier to confuse cow's milk and soy protein allergies with celiac disease, but these allergic conditions are rare and primarily occur in young children. Despite these limitations, small intestinal biopsies are recommended even for individuals who have abnormal antibody tests for celiac disease. (See discussion that follows.)

Specific antibody tests for celiac disease

Antibodies are proteins that are produced by the immune system to fight viruses, bacteria, and other organisms that infect the body. Sometimes, however, the body produces antibodies against non-infectious substances in the environment (for example, in hay fever) and even against its own tissues (autoimmunity).

Blood tests that are specific for celiac disease include endomysial antibodies, anti-tissue transglutaminase antibodies, and anti-gliadin antibodies. In patients with celiac disease, anti-gliadin antibody is an antibody produced against gliadin in the diet and endomysial and anti-tissue transglutaminase antibodies are antibodies produced against the body's own tissues.

Endomysial antibodies and anti-tissue transglutaminase antibodies are highly reliable in diagnosing celiac disease. An individual with abnormally elevated endomysial and anti-tissue transglutaminase antibodies has a greater than 95% chance of having celiac disease. Anti-gliadin antibodies are less reliable and have a high false positive rate. Thus a person with an abnormally elevated anti-gliadin antibody level does not necessarily have celiac disease. Nevertheless, anti-gliadin antibody levels are useful in monitoring the response to treatment because anti-gliadin antibody levels usually begin to fall within several months of successful treatment of celiac disease with a gluten free diet.