Lipase (Serum) Test

The Lipase Test measures serum lipase, the digestive enzyme released from pancreatic acinar cells when the pancreas is acutely injured. It is the principal biochemical test for diagnosing acute pancreatitis, and is ordered in the assessment of acute epigastric or upper abdominal pain, particularly pain radiating to the back with nausea and vomiting. A lipase above three times the upper limit of normal, in the presence of characteristic pain, satisfies the biochemical criterion for the diagnosis. Within pancreatic assessment, lipase has clearly displaced amylase as the test of choice: it is more sensitive and more specific, it is not raised by salivary gland disease, and its longer half-life keeps it elevated for 8 to 14 days, so it still detects pancreatitis in patients presenting several days after symptom onset when amylase may already have normalised. Measuring both enzymes together adds little and is generally unnecessary. Two limitations matter in practice. First, lipase establishes the diagnosis but says nothing about severity or prognosis — the degree of elevation does not track with disease course, so severity is assessed clinically and radiologically, and serial lipase measurement to follow recovery is not useful. Second, lipase is not exclusively pancreatic in its differential: modest elevations occur in renal impairment, bowel obstruction or perforation, mesenteric ischaemia, and cholecystitis, so an isolated raised lipase without compatible symptoms should not be equated with pancreatitis. It is also distinct from faecal pancreatic elastase-1, which assesses chronic exocrine insufficiency rather than acute inflammation.