Blood Tests for Diagnosis of Celiac Disease
The first step in the diagnosis of celiac disease is usually a set of blood tests to measure levels of certain autoantibodies. Unlike antibodies, which attack foreign substances in the body, autoantibodies attack the body’s own tissues. The autoantibodies that doctors usually measure to test for celiac disease are called immunoglobulin A (IgA), anti-tissue transglutaminase (tTGA), and IgA anti-endomysium antibodies (AEA).
If the autoantibody levels turn out to be high, the patient probably has celiac disease. Unfortunately, however, if the levels are not elevated, it is not safe to conclude that the patient does not have celiac disease.
Biopsy for Diagnosis of Celiac Disease
The next step, if the tests or symptoms suggest celiac disease, is a small bowel biopsy. (“Small bowel” is another term for “small intestine.”) Small bowel biopsies are usually done to confirm the diagnosis, even when the blood tests are positive. If the patient has positive blood tests and biosy-proven dermatitis herpetiformis, however, a small bowel biopsy is not required.
Ordinarily, the lining of the small intestine (the mucosa) is covered with hairlike projections called villi. In patients with untreated celiac disease, the inflammation that develops in response to gluten causes the villi to shrink and flatten. This effect can be seen when tissue samples taken from the small intestine by biopsy are examined under a microscope, as shown in Figure 1.
While the patient is asleep, the doctor passes a long, narrow tube called an endoscope through the patient’s mouth and stomach, into the small intestine. The doctor can then pass instruments through the endoscope to remove tissue samples and also to take photographs. Later, a pathologist will study the tissue samples to check for the classic signs of shrinkage and flattening of the villi.
Confirmation of the Diagnosis: Improvement on the Gluten-Free Diet
The final piece that confirms the diagnosis of celiac disease –- after the positive biopsy result –- is improvement of health with the gluten-free diet.Sources:
National Digestive Diseases Information Clearinghouse.
NIH Consensus Development Conference on Celiac Disease.
The University of Maryland Center for Celiac Disease Research.
Figure 1. “Reprinted with permission from the University of Iowa Health Care’s magazine for physicians Currents, 2003, 4:2(Spring): David Elliott. Management of celiac disease.
