Celiac disease, also called coeliac disease or gluten intolerance, is an abnormal immune response to dietary gluten that destroys villi in the small intestine. Gluten is a protein in wheat, barley and rye. More prevalent in those of Northern European descent, celiac disease affects an estimated 2 million Americans, as noted by the National Institutes of Health. Symptoms may mimic inflammatory bowel disease or chronic fatigue syndrome. Skin rashes can also be a symptom of celiac disease. Tools used to diagnose this condition include blood tests, biopsies and fecal analysis, but inconclusive results are common and need to be evaluated in the context of dietary control and symptoms.
Blood Tests
Two types of blood tests are used to diagnose celiac disease. One looks for endomysial antibodies for gliadin, a gluten-derived toxin. Another detects antibodies for the intestinal enzyme tissue transglutaminase. Blood tests measure reactions to gluten; those with celiac disease who adhere to a strict gluten-free diet would test negative.
Because celiac disease damages the villi in the small intestine, some molecules that should not leak into the bloodstream do so, because the gut becomes more permeable. Researchers Johnston and Smye of Belfast City Hospital in Northern Ireland conducted a study of intestinal permeability tests in celiac disease. In the study, titled "Clincal Laboratory: Intestinal Permeability Tests in Coeliac Disease," they discovered that this aspect of gluten intolerance can be tested by giving subjects a hyperosmolar solution containing two sugar molecules, lactulose and mannitol. The scientists were able to determine if the sugars leaked through the small intestine by looking for them in the blood. This intestinal permeability test could provide a less invasive alternative to biopsy.
Biopsy
If blood tests are positive, results are usually confirmed by a biopsy of the small intestine. This involves threading a flexible tube, called an endoscope, through the mouth and stomach into the bowel. The endoscope is equipped with a light and tiny video camera, so that doctors can view the gastrointestinal tract and take tissue samples. The samples are evaluated for the villous damage that is characteristic of celiac disease. However, avoidance of dietary gluten can heal intestinal damage, making the biopsy more accurate for patients who have not adopted a gluten-free diet. A positive blood test and a negative biopsy may indicate a false blood test result or may be consistent with latent celiac disease.
A biopsy is also performed on skin samples of dermatitis hepeteformis, an intensely itchy rash associated with gluten intolerance. Most often found on the surfaces of both shins, knees, buttocks and elbows, treatment centers around a gluten-free diet.
Fecal Analysis
According to the National Institutes of Health, an estimated 4 to 12 percent of first-degree family members of confirmed celiac cases also have gluten intolerance. The condition is linked to type 1 diabetes and other autoimmune conditions. Family members are most often screened by blood tests, but reactive antibodies may also be found in the intestines and are detectable by a stool sample analysis. Proponents of this test, such as Dr. Kenneth Fine, gastroenterologist and Medical Director of EnteroLab in Dallas, Texas, say it can detect gluten reactions before antibodies are present in the bloodstream and is sensitive enough to provide confirmation, even in those on a gluten-free diet.
References
- National Digestive Diseases Information Clearinghouse: Celiac Disease
- PubMed: "Clincal Laboratory: Intestinal Permeability Tests in Coeliac Disease"; Johnston and Smye et al; 2001
- Medscape: "Diagnosis & Treatment of Celiac Disease in Children"; Patricia L. Jackson Allen, MS, RN; 2005
- EnteroLab: FAQ Gluten Intolerance
