The diagnosis of celiac disease can sometimes be difficult. Celiac is also known as "the great imitator" because many of its symptoms can resemble those of numerous other health conditions. Some people will experience skin rashes, others may have more neurological or psychological symptoms, while still others will demonstrate the more classic digestive symptoms--diarrhea and weight loss--associated with celiac. This makes accurate means of testing for celiac key to its diagnosis.
Blood Testing
Blood testing is often the first means doctors turn to when they suspect celiac disease. The most common tests look at levels of endomysial and tissue transglutaminase IgA antibodies. These are antibodies that the immune system makes to its own tissues, after gluten triggers an autoimmune response. A test for total IgA levels is also often included to ensure that the body is mounting an effective immune response, since low IgA levels can cause low--interpreted as "negative"--endomysial antibody tests. The endomysial IgA antibody test is considered a very specific and sensitive test for celiac disease; it has a much greater likelihood of determining if someone has celiac with less chance of false negatives--that is, a negative test result when someone does have celiac. Despite negative blood test results, based on symptoms, your doctor may suggest further testing--usually through endoscopy--if he strongly suspects celiac disease. Remember that if you have been following a gluten-free diet for several months, blood testing may also not show any evidence of celiac. In this regard, blood testing can be used to monitor a celiac's adherence to a gluten-free diet.
Endoscopy
The endoscopy, wherein a doctor inserts a thin, flexible tube down your esophagus and past your stomach into your small intestines, is still considered the gold standard for diagnosis of celiac disease. During this procedure, the doctor will remove small tissue samples from the lining of the small intestine to be sent to a lab for analysis. Those who have not been ingesting gluten for many months with not show intestinal damage consistent with celiac disease. This could lead to a false negative diagnosis, when in fact celiac disease does exist.
Genetic Testing
Several laboratories and hospitals now conduct genetic testing for celiac disease. Like many other health conditions, including lupus and rheumatoid arthritis, celiac disease demonstrates specific genetic sequences--namely HLA-DQ2 and HLA-DQ8--in the DNA of those who are susceptible. Genetic testing can utilize either blood or saliva samples to look for these genes. The concept is relatively simple; if you have the genes for celiac disease, you may develop celiac sometime in your life, or you may already have celiac disease. If you don't have the genes for celiac, it is unlikely that you will develop celiac. Genetic testing is not used as a final diagnosis for celiac disease though; it is only designed to give you information on your potential for developing celiac.
