Celiac Disease Diagnosis & Tests
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.
Blood tests for malabsorption and vitamin deficiencies
Malabsorption reduces the absorption of protein and causes a reduction in blood protein levels. This can be seen commonly as a reduced blood level of albumen, the most concentrated protein in blood. Other proteins in blood -- pre-albumen and transferrin -- also may be reduced.
Intestinal malabsorption can lead to deficiencies and low blood levels of iron, calcium, vitamin B12, folate, and the fat-soluble vitamins (A, D, E, and K). These deficiencies, in turn, can lead to other blood test abnormalities, such as:
- Iron deficiency anemia: Iron is an important component of hemoglobin in red blood cells. When iron is deficient, production of red blood cells is impaired, and anemia develops. Iron deficiency anemia can occur through loss of blood (with its iron-containing red blood cells) or lack of intestinal iron absorption. Heavy menstrual bleeding, GI tract bleeding, and cancer of the colon that bleeds into the intestine are three common causes of iron deficiency anemia due to blood loss. Celiac disease causes iron deficiency anemia by reducing intestinal iron absorption. In fact, iron deficiency anemia can be an important clue to the presence of celiac disease.
- Abnormally prolonged prothrombin time (PT): PT is a blood test that measures how quickly blood clots. Clotting of blood requires special proteins or clotting factors, many of which are made by the liver. Formation of clotting factors by the liver requires vitamin K. When vitamin K absorption from the intestine is reduced, as in celiac disease, the production of clotting factors by the liver is inadequate, and blood clotting is delayed. Delayed clotting is reflected in an abnormal PT, and individuals with an abnormal PT have a higher risk of abnormal or excessive bleeding.
Iron deficiency anemia, abnormal PT, steatorrhea, and low iron and vitamin levels can occur in diseases other than celiac disease. Therefore, the presence of these abnormalities only raises the suspicion of celiac disease, but does not specifically diagnose celiac disease.