Celiac Disease Diagnosis & Tests
Small intestinal biopsy
People who test positive for celiac disease antibodies, or who have a high probability of celiac disease regardless of the results of the blood tests, should have a small intestinal biopsy to confirm the diagnosis. A small intestinal biopsy is performed with an esophagogastroduodenoscopy (EGD). During an EGD, the doctor inserts a long, flexible viewing endoscope through the mouth and into the duodenum (the first part of the small intestine, which is connected to the stomach). A long, flexible biopsy instrument then can be passed through a small channel in the endoscope to obtain samples of the intestinal lining of the duodenum. A pathologist evaluates the tissue samples for loss of villi and other characteristics of celiac disease, such as an increased number of lymphocytes.
Why is it important to accurately diagnose celiac disease?
Diagnosis of celiac disease should be firmly established before starting a person on a gluten-free diet. Here's why:
- The gluten-free diet requires avoiding wheat, barley, and rye -- products that are dietary staples, at least in the U.S.
- Patients with irritable bowel syndrome (IBS) may experience improvements in bloating, abdominal pain, and diarrhea with a gluten-free diet. These patients may be misdiagnosed as having celiac disease. Without confirmation of celiac disease by small intestinal biopsy, they may be unnecessarily committed to lifelong gluten restriction.
- A gluten-free diet can lower blood antibody levels and allow the microscopic appearance of the small intestine to lose the typical appearance of celiac disease, complicating subsequent efforts at making a firm diagnosis of celiac disease.
How are malabsorption and malnutrition evaluated in celiac disease?
Celiac disease causes malabsorption of nutrients and leads to malnutrition. Tests are available that help in the evaluation of malabsorption and malnutrition; however, because other diseases can cause both malabsorption and malnutrition, these tests cannot be used to diagnose celiac disease.
Stool examination for malabsorption
Stool from patients with celiac disease often contains many globules of fat -- a condition called steatorrhea -- that can be viewed under a microscope using a dye to make them visible. To conclusively diagnose steatorrhea, however, stool is collected over a 72-hour period, and the fat in the stool is chemically measured and quantified.
Because malabsorption and steatorrhea can occur with other intestinal diseases (such as small intestinal bacteria overgrowth, prior small intestinal resection, extensive Crohn's disease of the small intestine, and chronic pancreatitis), stools with large amounts of fat raise the suspicion of celiac disease but cannot be used to diagnose celiac disease.