What types of malabsorption are diagnosed using D-xylose, lactulose with hydrogen breath test, fecal elastase, Sudan (stain) test, and SeHCAT (tauroselcholic acid scan)?

From the Guidelines

These tests are used to diagnose different types of malabsorption disorders, including carbohydrate, fat, protein, and bile acid malabsorption, which can help identify conditions such as celiac disease, bacterial overgrowth, pancreatic insufficiency, and bile acid diarrhea. The D-xylose test evaluates small intestinal absorption capacity, particularly for carbohydrates, and can help diagnose conditions like celiac disease or bacterial overgrowth 1. The lactulose hydrogen breath test detects carbohydrate malabsorption and small intestinal bacterial overgrowth by measuring hydrogen produced when unabsorbed lactulose is fermented by bacteria 1. Fecal elastase measures pancreatic enzyme levels in stool to identify pancreatic exocrine insufficiency, which causes fat and protein malabsorption 1. The Sudan stain test detects fecal fat to diagnose fat malabsorption from various causes including pancreatic insufficiency, bile acid deficiency, or mucosal disorders 1. The SeHCAT scan specifically evaluates bile acid malabsorption by measuring retention of a radioactive bile acid analog, identifying conditions like bile acid diarrhea 1.

Key Points

• The D-xylose test is used to evaluate small intestinal absorption capacity, particularly for carbohydrates.
• The lactulose hydrogen breath test is used to detect carbohydrate malabsorption and small intestinal bacterial overgrowth.
• Fecal elastase is used to measure pancreatic enzyme levels in stool and identify pancreatic exocrine insufficiency.
• The Sudan stain test is used to detect fecal fat and diagnose fat malabsorption.
• The SeHCAT scan is used to evaluate bile acid malabsorption and identify conditions like bile acid diarrhea.

Diagnosis and Treatment

These tests are complementary and are often used in combination to pinpoint the specific cause of malabsorption symptoms, which can include diarrhea, weight loss, and nutritional deficiencies 1. For example, a patient with suspected bile acid diarrhea may undergo a SeHCAT scan to confirm the diagnosis, and then be treated with bile acid sequestrants such as colestipol 1. Similarly, a patient with suspected pancreatic insufficiency may undergo fecal elastase testing, and then be treated with pancreatic enzyme replacement therapy 1.

Recommendations

The choice of test depends on the suspected underlying cause of malabsorption, and a combination of tests may be necessary to establish a definitive diagnosis. For example, if lactose maldigestion is suspected, hydrogen breath testing or withdrawal of dietary lactose/carbohydrates from the diet may be recommended 1. If fat malabsorption is suspected, fecal elastase testing may be recommended 1. If bile acid malabsorption is suspected, a SeHCAT scan may be recommended 1.

From the Research

Types of Malabsorption Tests

The following tests are used to diagnose different types of malabsorption:

• D-xylose test: used to diagnose malabsorption due to intestinal mucosal disease or damage 2, 3
• Lactulose with hydrogen breath test: used to diagnose small intestinal bacterial overgrowth (SIBO) 4, 5
• Fecal elastase test: used to diagnose pancreatic insufficiency
• Sudan stain test: used to diagnose steatorrhea (excess fat in the stool)
• SEHCAT scan: used to diagnose bile acid malabsorption

Test Specifics

• The D-xylose test measures the level of D-xylose, a sugar, in the blood or urine after ingestion, to assess intestinal absorption 2, 3
• The lactulose with hydrogen breath test measures the level of hydrogen in the breath after ingestion of lactulose, to assess SIBO 4, 5
• The fecal elastase test measures the level of elastase, an enzyme, in the stool, to assess pancreatic function
• The Sudan stain test measures the level of fat in the stool, to assess steatorrhea
• The SEHCAT scan measures the level of bile acids in the intestine, to assess bile acid malabsorption

Test Sensitivities and Specificities

• The D-xylose test has a sensitivity of 0.86 and specificity of 1 for diagnosing malabsorption 2
• The lactulose with hydrogen breath test has a sensitivity of 58% and specificity of similar to the xylose breath test for diagnosing SIBO 4
• The fecal elastase test has a high sensitivity and specificity for diagnosing pancreatic insufficiency, but the exact values are not provided in the studies
• The Sudan stain test has a high sensitivity and specificity for diagnosing steatorrhea, but the exact values are not provided in the studies
• The SEHCAT scan has a high sensitivity and specificity for diagnosing bile acid malabsorption, but the exact values are not provided in the studies