The First Step: Antibody Testing
Specific antibody blood tests are the initial step in screening for celiac disease. These tests rely on the presence of antibodies in the bloodstream caused by a reaction to gluten. Because of the importance of long-term gluten consumption for an accurate diagnosis, it is critical that you consult your doctor and complete the necessary tests before starting a gluten-free diet.
There are many screening tests for celiac disease but the most accurate and commonly used is the tTg-IgA test:
Anti-tissue transglutaminase antibody (tTG): This test is commonly used whether or not symptoms are present; currently the most sensitive test available. It is estimated that 98% of people with celiac disease have a positive tTG test. There is a risk of a false negative especially for people with associated autoimmune disorders like Type I Diabetes. There are other antibody tests available to double-check for potential false positives or false negatives.
- Anti-endomysial antibody (EMA – IgA): EMA-IgA are very specific for celiac disease: it is estimated that a person with an elevated titer of EMA is almost guaranteed to have celiac disease. However, this test is not as sensitive as the tTG-IgA. About 5-10% of people with celiac disease do not have a positive EMA test. (original draft)
- Total serum IgA: This test is used to check for IgA deficiency, a condition that causes a false negative for the tests listed above. IgA deficiency is diagnosed when someone has a total serum IgA test and the results are very close to zero (less than 10mg/dl). This is not a test for celiac disease, but a means to make a more accurate diagnosis. (original draft)
- Anti-deaminated gliadin peptide (DGP): This test can be used to further screen for celiac disease in individuals with IgA deficiency or people who test negative for tTg or EMA antibodies.
- Anti-gliadin antibody (AgA): This test is not considered specific enough for adult but can be used for children under 2 because tTG and EMA antibodies may be absent at that stage of development.
While it is very rare, it is possible for someone with celiac disease to have negative antibody test results. If your tests were negative but you continue to experience symptoms, consult your physician and undergo further medical evaluation.
When antibody results and biopsy are inconclusive, or when the patient has already started a gluten-free diet, genetic testing may be used to determine if celiac disease is a possibility. Genetic test will not confirm a diagnosis of celiac disease. 35% of people have either HLA DQ2 or DQ8 yet it is estimated that only 1% of people in the general population have celiac disease.
Genetic tests determine if the patient has the genes necessary for celiac disease to develop. The presence of the HLA DQ2 and HLA DQ8 genes show that a celiac disease diagnosis is possible, though many people with the genes do not actually develop celiac disease. Genetic testing does not diagnose celiac disease but the absence of DQ2 and DQ8 excludes a celiac disease diagnosis, allowing individuals to pursue an alternate diagnosis for their symptoms.
Keep in mind that positive antibody or genetic test results only suggest the presence of celiac disease—the test results cannot confirm it. If these screening tests come back positive, the next step in diagnosing celiac disease is to get a biopsy of the small intestine. For more information on this procedure, see our Diagnosis page.
Finding the Right Doctor
The Celiac Disease Foundation can help you find the right doctor to discuss symptoms, diagnose, and treat celiac disease. Please refer to our Celiac Centers and Celiac Experts page for a listing of experienced healthcare professionals and celiac centers.