What are the laboratory tests for assessing pancreatic function?

From the Guidelines

The most appropriate initial test for assessing pancreatic function is the fecal elastase test, as it is a reliable and convenient non-invasive test that can detect pancreatic insufficiency. This is based on the latest guidelines and evidence, including the 2023 study published in Gastroenterology 1. The fecal elastase test is recommended as the test of first choice in patients who present with diarrhea of putative pancreatic origin, as it offers the advantages of acceptable reliability and convenience without the need for prolonged urine collections.

Key Points to Consider

• The fecal elastase test is a non-invasive test that measures the level of elastase in the stool, which is an enzyme produced by the pancreas.
• A fecal elastase level <100 mg/g of stool provides good evidence of exocrine pancreatic insufficiency (EPI), and levels of 100–200 mg/g are indeterminate for EPI 1.
• Fecal fat testing is rarely needed and should only be performed when on a high-fat diet, as it can detect fat malabsorption and suggest pancreatic insufficiency.
• Blood tests for nutritional deficiencies, such as vitamins A, D, E, K, and B12, may indicate malabsorption due to pancreatic dysfunction.
• For endocrine function, fasting blood glucose, hemoglobin A1c, and glucose tolerance tests can help evaluate insulin production.

Additional Considerations

• The pancreas must lose significant function (usually over 90% for exocrine function) before clinical symptoms appear, making laboratory assessment crucial for early detection and management of pancreatic disorders.
• Direct pancreatic function tests, such as the secretin stimulation test, may be used in specialized settings to measure bicarbonate concentration in duodenal fluid after secretin administration.
• The latest guidelines and evidence should always be consulted to ensure the most up-to-date and effective approach to assessing pancreatic function.

From the Research

Pancreatic Function Tests

• The diagnosis of acute pancreatitis is usually based on the presence of abdominal pain and elevated levels of serum amylase and/or lipase 2.
• Serum lipase offers a higher sensitivity than serum amylase in diagnosing acute pancreatitis, and it also offers a larger diagnostic window than amylase 2.
• Measurement of fecal elastase-1 is recommended as the most suitable test for the initial assessment of pancreatic function 3.
• The secretin-caerulein test remains the gold standard for assessing pancreatic function, especially in patients with mild to moderate impairment of pancreatic function 3.

Laboratory Diagnostic Tests

• The serum amylase is the cornerstone laboratory test used in establishing the diagnosis of acute pancreatitis, but it has limitations in sensitivity and specificity 4.
• The serum lipase level may be especially useful in patients with alcohol-induced acute pancreatitis 4.
• A new urinary test strip that uses trypsinogen-2 may have a role in establishing the diagnosis of acute pancreatitis 4.
• Serum amylase, serum lipase, and urinary trypsinogen-2 appear to have similar sensitivities and specificities for the diagnosis of acute pancreatitis 5.

Test Characteristics

• The sensitivity of serum amylase, serum lipase, and urinary trypsinogen-2 for the diagnosis of acute pancreatitis is around 0.72-0.79 5.
• The specificity of serum amylase, serum lipase, and urinary trypsinogen-2 for the diagnosis of acute pancreatitis is around 0.89-0.93 5.
• The post-test probability of a positive test for serum amylase, serum lipase, and urinary trypsinogen-2 is around 67-74% 5.
• The post-test probability of a negative test for serum amylase, serum lipase, and urinary trypsinogen-2 is around 7-8% 5.