The P3 iso-enzyme of serum amylase in the management of patients with acute pancreatitis.

The concept of the P3 index and its use in separating acute pancreatitis from other causes of hyperamylasaemia is described. The mean P3 index of 12 healthy volunteers was 94.8 per cent. All 69 patients with acute pancreatitis had a P3 index below 80 per cent with a mean value of 67.9 per cent. The P3 index is abnormal longer than the raised serum amylase, which increases diagnostic accuracy. Causes of hyperamylasaemia other than acute pancreatitis have been studied and most patients have a P3 index above 80 per cent, although certain false positive values have been obtained. No patient with acute pancreatitis has had a P3 index above 80 per cent on admission. Five cases of acute pancreatitis have been studied in whom the P3 index remained abnormal; all had continuing pancreatic disease, usually with pseudocyst formation. The test has proved most valuable in identifying those patients at risk of developing subsequent problems. To date, the test cannot be relied upon to help in deciding upon the severity of an attack of acute pancreatitis.