Serum pancreatic isoamylase estimation by the inhibitor method as a diagnostic test for chronic pancreatitis.

The diagnosis of chronic pancreatitis is often difficult to establish and may involve invasive diagnostic procedures. Serum pancreatic isoamylase has been estimated by the inhibitor method in controls and in 38 patients with known chronic pancreatitis in order to evaluate its use as a diagnostic test. The mean pancreatic isoamylase in those with chronic pancreatitis (68 +/- 77 IU/l) was significantly lower (p less than 0.005) than in controls (113 +/- 60 IU/l). The diagnostic sensitivity of pancreatic isoamylase was 50% (compared to total amylase 9%) and had a specificity of 95%. Stimulation tests with cholecystokinin and secretin failed to increase the sensitivity of the test. A low value of pancreatic isoamylase strongly supports a diagnosis of chronic pancreatitis and may obviate the need for further investigation.