Amylase assays measure total activity without differentiating the relative contributions of pancreatic- and salivary-type
amylase isozymes. Since
polyacrylamide electrophoresis allows identification of salivary-and pancreatic-type isoxymes and their respective variants, serum and urine specimens from patients with the clinical diagnoses of
mumps (4),
pancreatitis (16), or undiagnosed hyperamylasemias (5) were compared with specimens from control subjects. Patients with
mumps had elevations of salivary-type
isozymes, while those with
pancreatitis had elevations of pancreatic-type
isozymes. Elevation of salivary-type
isozymes was identified in the five patients who had undiagnosed hyperamylasemias; among these, the
isozymes of two originated in neoplastic ovarian tissue and those of three, probably in the salivary glands.
Amylase isozyme differentiation cannot unamibiguously identify the tissue source of
hyperamylasemia. However, in patients whose
hyperamylasemia is of unknown etiology or who respond atypically to
therapy,
amylase electrophoresis provides identification of the elevated
isozyme type, thus providing the basis for the rational selection of further diagnostic procedures.