The value of routine pancreatic iso-amylase measurements in the diagnosis of pancreatitis.

The value of serum pancreatic iso-amylase (Pi) measurements in the clinica diagnosis of pancreatitiss was assessed using a wheat inhibitor kit (Phadebas) and cellulose acetate membrane (CAM) electrophoresis. Wheat inhibition totally suppressed Pi activity in the sera of 3 healthy subjects with substantial Pi bands on electrophoresis. Reference intervals for Pi, salivary iso-amylase (Si) and total alpha-amylase were established from the sera of 61 healthy subjects using CAM electrophoresis. Sera from 47 patients were assayed. Twenty-three had proven acute pancreatitis (AP) and 24 had established chronic pancreatitis (CP). All patients with AP had elevated serum Pi levels. Fifteen of these patients had a low P3 index, which ranged between 55.8% and 82.6% with a mean of 67.1%. An index of less than 100% indicates the presence of P3 isoamylase. P3 iso-amylase only occurred in patients with AP. Thirteen of these 15 patients did not have Si in their serum. In 20 of 24 patients with CP, serum Pi was reduced and in 4 it was at the lower limit of the reference interval. Ten of these patients had raised Si levels. In 13 of these patients the total amylase level was normal; in 4 it was increased and in 7 it was reduced. It is concluded that raised Pi and the P3 index are useful in the diagnosis and monitoring of AP; reduced Pi is highly suggestive of CP, and the use of total alpha-amylase levels alone can be misleading.