Use of Serum Amylase Isoenzymes in Evaluation of Pancreatic Function

Abstract

Amylase isoenzyme patterns were evaluated in serum, urine, and duodenal fluid from 19 patients with cystic fibrosis (CF) and normal subjects. Two thirds of the CF patients with absent pancreatic enzymes lacked a serum pancreatic isoamylase band, while the remainder had a markedly diminished pancreatic band when compared to the salivary isoamylase. In normal sera the pancreatic band is equal to or greater than the salivary band. In all patients with absent enzymes the diagnosis of abnormal pancreatic function could have been made by evaluation of serum isoamylase patterns thereby avoiding duodenal intubation or collection of 72-hour stools for proteolytic enzyme activities. The patients with normal pancreatic enzyme activities had normal serum zymograms. No CF patient had a low total serum amylase concentration. Total duodenal fluid amylase levels may be misleading in the evaluation of pancreatic function since the amylase may be of salivary origin. The advantages of this isoamylase method include (1) simplicity and noninvasiveness, requiring only a small blood sample; (2) specificity for pancreatic function; and (3) independence of pancreatic enzyme medication.