The serum amylase may be normal or only slightly increased in patients with hyperlipemic pancreatitis, due to an apparent inhibiting substance in the serum. This may cause a clinician to miss the diagnosis of pancreatitis unless certain steps are taken.
Ways to diagnose pancreatitis in the setting of hyperlipemia and a normal serum amylase value:
(1) Measure amylase activity in serial serum dilutions.
(2) Measure serum lipase levels, which may not be affected by the lipemia.
(3) Determine the amylase to creatinine clearance ratio (see Chapter 14).
Hyperlipidemia is associated with an inhibition of the serum amylase assay. Serial dilution reduces this inhibition and will unmask elevated amylase activity. A person without pancreatitis will show reduced activity comparable to the degree of dilution.
An amylase to creatinine clearance > 5.5% favors the diagnosis of acute pancreatitis, although the test may be affected by many factors.
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