Fast liver alkaline phosphatase isoenzyme in diagnosis of malignant biliary obstruction.

Fast liver alkaline phosphatase isoenzyme was measured by cellulose acetate electrophoresis in the sera obtained from 84 patients with specific hepatobiliary diseases and 10 control subjects. The mean value of this isoenzyme in patients with malignant extrahepatic obstruction was 130.58 +/- 107.08 U/L, significantly higher than that of patients with benign extrahepatic obstruction (65.63 +/- 34.14 U/L), as well as patients with intrahepatic cholestasis and infiltrative liver cancers (65.31 +/- 38.11 U/L and 48.47 +/- 36.85 U/L, respectively). Furthermore, we could not detect this isoenzyme in normal individuals. When 100 U/L was used as a cut-off value to discriminate between patients with malignant extrahepatic obstruction and the remaining hepatobiliary disorders, the sensitivity, specificity and accuracy of the test were 63 per cent, 84 per cent and 80 per cent, respectively. It is concluded that the fast liver isoenzyme could be a useful marker in diagnosis of malignant extrahepatic obstruction.