How is celiac disease diagnosed?

Diagnosing celiac disease can be difficult because some of its symptoms are similar to those of other diseases, including irritable bowel syndrome, Crohn's disease, ulcerative colitis, diverticulosis, intestinal infections, chronic fatigue syndrome, and depression.

Recently, researchers discovered that people with celiac disease 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. To diagnose celiac disease, physicians test blood to measure levels of antibodies to endomysium and tissue transglutaminase.

If the tests and symptoms suggest celiac disease, the physician may remove a tiny piece of tissue from the small intestine to check for damage to the villi. This is done in a procedure called a biopsy: the physician eases a long, thin tube called an endoscope through the mouth and stomach into the small intestine, and then takes a sample of tissue using instruments passed through the endoscope. Biopsy of the small intestine is the best way to diagnose celiac disease.

Screening

Screening for celiac disease involves testing asymptomatic people for the antibodies (see above). Americans are not routinely screened for celiac disease. However, because celiac disease is hereditary, family members--particularly first-degree relatives--of people who have been diagnosed may need to be tested for the disease. About 10 percent of an affected person's first-degree relatives (parents, siblings, or children) will also have the disease. The longer a person goes undiagnosed and untreated, the greater the chance of developing malnutrition and other complications.

source: http://digestive.niddk.nih.gov/ddiseases/pubs/celiac/index.htm