What blood tests are needed to help diagnose celiac disease?
Researchers have discovered that people with celiac disease who eat gluten have higher than normal levels of certain antibodies in their blood. Antibodies are produced by the immune system in response to substances that the body perceives to be threatening. Think of antibodies as a sending out a warning signal to the body—only in the case of an autoimmune disorder like celiac disease, the warning signal sounds for something that is supposed to be safe—the proteins in wheat, rye and barley that are generically known as "gluten."
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Which tests do I need?
| Screening Test |
| Anti-Tissue Transglutaminase (tTG-IgA) -- A screening test is commonly used when an individual is in a risk group for celiac disease, whether or not he/she has symptoms. This test is usually the one offered for celiac screening events, as it is the most sensitive test available. |
| Other Tests |
| Total Serum IgA -- This one tests for IgA deficiency, a condition which can affect the accuracy of an antibody test |
| Anti-endomysial antibody test (EMA-IgA) -- EMA-IgA are very specific for celiac disease but they are not as sensitive as the tTG-IgA. |
| HLA-DQ2 and HLA-DQ8 gene tests -- The "gene tests" are not antibodies. They can be used to exclude celiac disease (if negative) in doubtful cases. |
| Note: |
| Anti-gliadin antibodies (AGA-IgG and AGA-IgA) are no longer used to test for celiac disease due to a low level of accuracy in people who have not yet been diagnosed. |
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If my positive antibody test suggests I may have celiac disease, how do I find out for sure?
If antibody tests and/or symptoms suggest celiac disease, the physician needs to establish the diagnosis by obtaining tiny pieces of tissue from the small intestine to check for damage to the villi. This is done in an endoscopic biopsy procedure. The physician eases a long, thin tube called an endoscope through the mouth and stomach into the small intestine, and then takes samples of the tissue using instruments passed through the endoscope.
Biopsy of the small intestine is the only way to diagnose celiac disease.
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Why is it necessary to have the endoscopic biopsy?
It is important to know that the blood testing can only confirm that you do not have celiac disease. This is why the biopsy is necessary if your test results are positive, to confirm the results. It is important to definitively establish the presence of celiac disease and rule out the presence of other conditions, including food allergies, a far more common condition.
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What do I do if I have a negative blood test (or panel) but I'm still having symptoms?
While it is rare, it is possible for patients to have a negative antibody test results and still have celiac disease. IgA deficiency is one example where this could occur. Further medical evaluation is important for anyone who is still experiencing symptoms, to establish the diagnosis or to rule out celiac disease as a part of establishing another diagnosis.
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