Relation between serum pancreatic isoamylase concentration and pancreatic exocrine function.

Serum pancreatic isoamylase concentrations were compared to secretory and clinical evidence of pancreatic insufficiency in 19 consecutive alcoholic patients undergoing pancreatic stimulation testing for suspected pancreatic insufficiency. In patients with normal total serum amylase levels, there was a good correlation (r = 0.83) between serum pancreatic isoamylase activity and stimulated pancreatic secretion of amylase and the 8 patients with a low pancreatic isoamylase concentration had markedly diminished pancreatic secretion of amylase, lipase, and bicarbonate. However, patients with elevated total serum amylase activity frequently had extremely poor pancreatic exocrine function despite normal or elevated levels of pancreatic serum isoamylase. Thus, the finding of a subnormal serum concentration of pancreatic isoamylase provides strong evidence for pancreatic exocrine insufficiency; however, a normal or elevated serum pancreatic isoamylase activity cannot be used as evidence for normal pancreatic exocrine function.