Serum Lipase is the Enzyme of Choice for Diagnosing Pancreatitis
Serum lipase should be measured to check for pancreatitis, as it is more sensitive, specific, and has a longer diagnostic window than amylase. 1
Primary Diagnostic Enzyme
Serum lipase is the gold standard enzyme for diagnosing acute pancreatitis, with the diagnostic cut-off defined as three times the upper limit of normal. 1
Lipase demonstrates superior sensitivity (79%) compared to amylase (72%) for detecting pancreatic injury. 2
The World Journal of Emergency Surgery guidelines emphasize that lipase is more reliable than amylase for pancreatic pathology. 1
Timing and Diagnostic Window
Lipase rises within 4-8 hours of pancreatic injury, peaks at 24 hours, and remains elevated for 8-14 days, providing a much larger diagnostic window than amylase. 1
In contrast, amylase rises within 6-24 hours, peaks at 48 hours, and normalizes within 3-7 days, making it less useful for late presentations. 1
This extended elevation period allows lipase to detect both early and late-stage acute pancreatitis. 2
Why Not Amylase?
Amylase lacks specificity because it is secreted not only by the pancreas but also by salivary glands, small intestine, ovaries, adipose tissue, and skeletal muscles. 1
In patients with elevated total amylase but normal lipase and trypsin, 90% of cases show elevation due to salivary amylase, yielding a clinical specificity of only 71% for serum total amylase. 3
Co-ordering both lipase and amylase provides little to no increase in diagnostic sensitivity or specificity, making dual testing unnecessary and wasteful. 4
Other Pancreatic Enzymes
Trypsin/trypsinogen and elastase can also be measured, but comparisons suggest trypsin is the most useful of the three serum tests (trypsin, amylase, lipase) when used together. 1
However, serum enzyme quantification is not of value in the diagnosis of chronic pancreatitis, as abnormally low serum enzymes are found in only 50% of cases with pancreatic insufficiency. 1
Clinical Application
A single lipase measurement on admission can exclude pancreatic injury with a negative predictive value of 99.8%. 2
If pancreatic trauma is suspected, serial lipase measurements every 6 hours may be helpful. 2
Persistently elevated lipase after 10 days from initial injury warrants close monitoring due to increased risk of pseudocyst formation. 2
Important Caveats
Lipase can be elevated in non-pancreatic conditions including renal disease, appendicitis, acute cholecystitis, bowel obstruction, and bowel ischemia. 1, 2
Neither lipase nor amylase can determine the severity or etiology of acute pancreatitis—clinical context and imaging are essential. 4
If no obvious cause is found and lipase is elevated, measure serum triglycerides, as levels >1000 mg/dl (>11.3 mmol/l) indicate hypertriglyceridemia-induced pancreatitis. 1, 2