A simple quantitative index of the P3 amylase isoenzyme in the diagnosis of acute pancreatitis.

Following a report (Legaz, M.E. and Kenny, M.A. (1976) Clin. Chem. 22, 57--62) that the amylase isoenzyme, P3, is elevated in acute pancreatitis but not in other conditions a new "P3 Index" is proposed. This reflects the ratio of the P3 isoenzyme to the major salivary isoenzyme, S1. The P3 Index eliminates the problems of peak overlap which prevent accurate detection or direct quantitation of P3. In acute pancreatitis a large increase in 3 produces a serum P3 Index of below 80%. Normal serum exhibits a P3 Index of above 80%. Most causes of hyperamylasaemia observed without acute pancreatitis also exhibited a P3 Index of above 80%. The P3 Index seems to be a useful aid to the diagnosis or exclusion of acute pancreatitis in patients exhibiting equivocal hyperamylasaemia.