Aged amylase: a valuable test for detecting and tracking pancreatic pseudocysts

D. W. Weaver, D. L. Bouwman, A. J. Walt, D. Clink, S. Sessions and J. Stephany

Amylase-rich fluid that incubates ("ages") within a pancreatic pseudocyst undergoes a change that can be detected by isoenzyme analysis of amylase from the serum. This aging is a result of deamination of the asparagine and glutamine residues on the amylase molecule. Eighteen of 20 patients with surgically proved pseudocysts had greater than 15% aged (deaminated) amylase in their serum. Levels of aged amylase returned to normal following treatment of their pseudocysts. Twenty of 23 patients with acute pancreatitis had levels of aged amylase below 15% (P less than .05). A criterion of 15% aged amylase resulted in 87% specificity, and 91% sensitivity for the diagnosis of pseudocysts. Because this test is noninvasive and easy to perform, it should become the ideal screen for patients at risk of development of pseudocysts, Endoscopic retrograde pancreatography, ultrasonography, and abdominal computed tomographic scanning should be reserved for confirmation of the diagnosis when the result of isoenzyme analysis is positive.