Efficiency in the diagnosis of acute pancreatitis increased by improved electrophoresis of amylase isoenzyme P3 on cellulose acetate.

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.