Serum from patients who have suffered
acute pancreatitis contains P3, an
isoenzyme of pancreatic-derived
amylase (EC 3.2.1.1). Heretofore, complete resolution of P3 from the major salivary
isoenzyme in serum, S1, has not been possible, thus compromising the diagnostic potential of P3 for
pancreatitis. I describe an electrophoretic method for the essentially complete resolution of P3 from S1 by including CaCl2, 1 mmol/L, in the Tris
barbiturate electrophoresis
buffer (25 mmol/L, pH 8.8). I evaluated the clinical utility of the method for 129 consecutive patients suspected of having
pancreatitis, by using receiver operating characteristic curve analysis for results for total
amylase, P2, and P3 activity. For a true-positive rate of 90% with a prevalence of
pancreatitis of 7.8%, the diagnostic efficiency was increased from 82% (total
amylase) to 91% (P2) to 98% (P3). Thus, including P3 activity in the diagnostic criteria will eliminate most false-positive results for
pancreatitis based on total
amylase activity alone, and should decrease the need for expensive radiologic procedures currently required to confirm the presence of
pancreatitis. I conclude that P3 can be of significant value in the differential diagnosis of
pancreatitis from other syndromes with
hyperamylasemia.