Variations in amylase isoenzymes and lipase during acute pancreatitis, and in other disorders causing hyperamylasemia

We compare the clinical value of assay of amylase (EC 3.2.1.1) isoenzymes with that of lipase (EC 3.1.1.3) in serum from patients with proven acute pancreatitis or with hyperamylasemia from other causes. In the former group we measured amylase, lipase, and isoamylases daily. Lipase and P(pancreas)-type isoamylases reached the highest mean values on the first day of an attack of acute pancreatitis (day one). Lipase declined rapidly, and by day four its mean activity was about the same as that of amylase and lower than that of the P-type isoamylases. Great inter-individual variations were found among patients with a similar clinical course. Of the 85 samples analyzed, amylase activity for 36 declined to within reference limits, but 18 of the 36 had high lipase activity, 18 had high P-type isoamylases activity, and 31 had P3 isoenzyme, which is not detectable in normal sera. Determination of isoamylases is a more sensitive index to acute pancreatitis than lipase assay and may be particularly useful when pancreatitis is suspected despite a normal total amylase activity. In the group of patients with hyperamylasemia from other origins, three had macroamylasemia, one had mumps, one had abdominal trauma without pancreatic injury, and one had pelvic inflammatory disease. The specific pattern of macroamylase on electrophoresis permitted a precise diagnosis of macroamylasemia; normal lipase had only ruled out pancreatitis. In the three other cases, lipase and isoamylases excluded pancreatic involvement.