Celiac Disease Diagnosis & Tests
How is celiac disease diagnosed?
Celiac disease is suspected in people who have signs or symptoms of malabsorption or malnutrition. Other diseases, however, can produce malabsorption and malnutrition, such as pancreatic insufficiency (a pancreas that is not able to produce digestive enzymes), Crohn's disease of the small intestine, and small intestinal overgrowth of bacteria. It is important, therefore, to confirm suspected celiac disease with appropriate testing.
Specific antibody tests for celiac disease
Antibodies are proteins that are produced by the immune system to fight viruses, bacteria, and other organisms that infect the body. Sometimes, however, the body produces antibodies against non-infectious substances in the environment (for example, in hay fever) and even against its own tissues (autoimmunity).
Certain blood tests should be performed initially to look for antibodies specific to celiac disease. If abnormally elevated levels of endomysial and anti-tissue transglutaminase antibodies are found, a person almost certainly has celiac disease. High levels of another antibody, anti-gliadin, may also be detected, but they don't necessarily mean a person has celiac disease. However, anti-gliadin antibody levels are useful in monitoring response to treatment, because they will usually begin to fall within several months of successful treatment of celiac disease with a gluten-free diet. Similarly, anti-endomysial antibody levels decrease on a gluten-free diet and often become negative in treated patients.
Who should undergo antibody blood tests for celiac disease?
Experts in the U.S. recommend antibody blood tests for people who have a higher likelihood than normal of having celiac disease. They include those with:
- Chronic diarrhea (diarrhea that does not resolve in three weeks), increased amount of fat in the stool (steatorrhea), and weight loss
- Excess gas, bloating, and abdominal distension
- Parents or siblings with celiac disease
- Growth retardation
- Unexplained iron deficiency anemia, or deficiency of folate and vitamin B12
- Skin blisters that are itchy (dermatitis herpetiformis)
- Recurrent, painful mouth sores (aphthous stomatitis)
- Diseases associated with celiac disease, such as type I (insulin-dependent) diabetes, autoimmune thyroid disease, rheumatoid arthritis, systemic lupus, ulcerative colitis, etc.
Small intestinal biopsy
People who test positive for celiac disease antibodies 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.