From the Guidelines
For evaluating diarrhea, I recommend starting with serum tests for celiac disease, such as IgA tissue transglutaminase, and considering tests for pancreatic exocrine function, like serum amylase and lipase, as well as serum fibroblast growth factor 19 for bile acid diarrhea. When evaluating diarrhea, it's essential to consider the underlying causes, including maldigestion, malabsorption, and inflammation. According to the AGA clinical practice guidelines 1, testing for celiac disease with IgA tissue transglutaminase is a strong recommendation with moderate-quality evidence. Some key points to consider when evaluating diarrhea include:
- Testing for celiac disease with IgA tissue transglutaminase and a second test to detect celiac disease in the setting of IgA deficiency, as recommended by the AGA 1
- Considering tests for pancreatic exocrine function, such as serum amylase and lipase, to detect pancreatic inflammation
- Measuring serum fibroblast growth factor 19 to identify bile acid diarrhea, as proposed in the AGA guidelines 1
- Interpreting results alongside clinical symptoms, as some conditions like chronic pancreatitis require significant pancreatic damage before enzyme levels become abnormal, as noted in the British Society of Gastroenterology guidelines 1.
From the Research
Serum Digestive Enzyme Tests for Diarrhea
To determine the appropriate serum digestive enzyme tests for diarrhea, several options can be considered:
- Elastase-1: This enzyme can be useful in diagnosing pancreatic exocrine insufficiency, which may be a cause of diarrhea 2. However, its levels may not always correlate with pancreatic function 3.
- Trypsin: This enzyme has been found to have a strict correlation with elastase-1 and lipase, and may be a more reliable index of pancreatic exocrine function 3.
- Lipase: Elevated lipase levels can be associated with pancreatic diseases, but can also be elevated in non-pancreatic conditions, making it less specific for pancreatitis 4.
- Amylase: Like lipase, amylase levels can be elevated in non-pancreatic conditions, and are not specific for pancreatitis 4.
Comparison of Serum Enzyme Assays
Studies have compared the diagnostic sensitivities of different serum enzyme assays, including:
- Serum amylase, lipase, trypsinogen, and elastase-1: These assays have been found to have varying degrees of sensitivity and specificity in diagnosing acute pancreatitis 5.
- Elastase 1 (E1) enzyme-linked immunosorbent assay (ELISA): This assay has been found to have a sensitivity of 80% and specificity of 96% in diagnosing acute pancreatitis, but its performance is inferior to lipase 6.
Considerations for Testing
When considering serum digestive enzyme tests for diarrhea, it is essential to:
- Evaluate the clinical context: The choice of test should be guided by the patient's clinical presentation and medical history.
- Consider multiple tests: A combination of tests may be necessary to accurately diagnose the underlying cause of diarrhea.
- Interpret results with caution: The results of serum enzyme assays should be interpreted in the context of the patient's overall clinical picture, as elevated levels can be associated with non-pancreatic conditions 4.