Estimation of serum pancreatic isoamylase: its role in the diagnosis of exocrine pancreatic insufficiency.

Using an inhibitor method, fasting levels of pancreatic isoamylase were measured in 46 healthy controls and in 218 patients undergoing a secretin-pancreozymin test for diagnostic purposes, and compared with immunoreactive trypsin (IRT). Exocrine pancreatic insufficiency was found in 82 of the patients. The specificity of both enzymes was high in patients with nonpancreatic diseases (pancreatic isoamylase: 98.5%, IRT: 96.3%). No patient with nonpancreatogenic steatorrhea had a low serum enzyme value. Sensitivity was, unfortunately, low in patients with exocrine pancreatic insufficiency (pancreatic isoamylase: 45.1%, IRT: 41.5%) and increased only slightly when patients after an acute attack of the disease, or patients with pseudocysts or older than 60 were excluded (pancreatic isoamylase: 67.9%, IRT: 58.5%). Although highly specific, pancreatic isoamylase measurement is not sensitive enough to be used as a screening test for exocrine pancreatic insufficiency but may be used to determine the etiology of steatorrhea.