<<Disclaimer: Verify this information before applying it to your situation.>> John Dennis asked me to explain the implications of serological tests in celiac disease. These are immunological tests. They are reflecting whether there is an activation of the immune system in the patients. The trigger for this immune response is the gliadin. The difference between a celiac and non-celiac individual is that a non-celiac does not have immune response to gliadin. If a patient has active disease and he/she is on a non-restricted diet the serological tests are positive, which means that he/she has high concentration of antibodies in his/her serum. We are performing three different tests: -anti-gliadin IgG antibody test -anti-gliadin IgA antibody test -anti-endomysium antibody test The most sensitive and specific test is the anti-endomysium test, however it can give false negative results in small children (<2 years of age) and in patients with selective IgA deficiency. IgA deficiency occurs in one out of 500-600 people. In IgA defificent patients only the anti-gliadin IgG test will be positive, and additional absorptive studies are necessary before the intestinal biopsy. The combination of these three antibody measurements allows us to reach an approximately 96% specificity and sensitivity. It means that we can miss 4% of patients if we rely on only the serological tests. If somebody on a gluten-free diet these tests become negative by 6 month of the gliadin-free diet. The decline of the initially high antibody levels may suggest a good compliance. In the absence of the "gliadin trigger" the immune system does not produce new antibodies, and generally it takes 6 months to eliminate the "old antibodies". A positive test during a long-term diet indicates accidental gluten consumption. The serological tests are useful in the diagnosis of celiac disease, and helpful in the estimation of strictness of the diet. If a celiac patients has some unusual symptom during the diet these tests can help to estimate whether these symptoms are related to the gliadin or we should look for some other reason. In Europe most of the patients have serological test results at the time of diagnosis, on diet, and during a rechallenge with gluten, which makes their management much easier. If you have any question concerning diagnostic tests in celiac disease me and my colleagues will be happy to answer them. We established a Celiac Center here at the University of Maryland to help children and adults with celiac disease all over the U.S. Karoly Horvath, M.D., Ph.D.