Serum isoamylase as a test for pancreatic insufficiency.

Total and pancreatic serum isoamylases were performed on 38 control subjects (21 non-smokers and 17 smokers) and 21 consecutive patients with pancreatic insufficiency before and after meal stimulation. There was no difference in the fasting or stimulated levels of total amylase (T), pancreatic isoamylase (P), or % P/T between smokers and non-smokers. The P/T ratio was significantly reduced in patients with pancreatic insufficiency when compared with each of the control groups (p less than 0.0005). Eleven of 21 patients with pancreatic insufficiency had raised total serum amylase, but none had a rise in the pancreatic fraction or P/T ratio. Our findings indicate that the T, P, and P/T ratio of serum amylase are not influenced by smoking or meal stimulation. A reduced P/T ratio in a patient with steatorrhoea suggests pancreatic insufficiency as the cause. Hyperamylasaemia in patients with pancreatic insufficiency does not necessarily imply a relapse.