BACKGROUND: Measurement of total serum amylase (AMY) is the most widely used biochemical test for the diagnosis of acute pancreatitis, but it is commonly considered a nonspecific marker. To improve the biochemical diagnosis of acute pancreatitis, lipase(LIP) and pancreatic amylase(PAMY) have been tested in recent years. The present study was designed to evaluate whether serum LIP and pancreatic PAMY tests could replace total amylase test to improve diagnostic efficiency in the evaluation of acute pancreatitis in patients with hyperamylasemia.
METHODS: LIP and PAMY values were determined in serum samples from 92 patients with hyperamylasemia. Reference values for each enzyme were derived from serum samples of 147 healthy subjects. The activities of LIP and PAMY in patients with various diseases were shown directly by the boxplot graph. The diagnostic accuracy of LIP and PAMY was defined as the area under the receiver operating characteristic (ROC) curve.  Their sensitivity and specificity in detecting acute pancreatitis at varying cutoff points were shown by the curve, and the best cutoff value for each enzyme was shown by the modified ROC curve. The diagnostic values of LIP, PAMY and LIP+AMY with each upper limit of reference range (ULR) were compared with the corresponding best cutoff values.  
RESULTS: The references values of LIP and PAMY were 12.2-47.6 U/L and 28-95 U/L, respectively. These values in patients with acute pancreatitis were higher than those patients with other diseases. The areas under the ROC curve (AUC) of LIP and PAMY were 0.799 and 0.792, respectively. With the best diagnostic cutoff point of maximum (sensitivity + specificity) -100%, we obtained values of 97.9 U/L(LIP97.9=2.06×ULR) for LIP and 209 U/L(PAMY209=2.20×ULR) for PAMY. The best cutoff values for LIP, PAMY and LIP+AMY demonstrated the specificity, positive predictive value, and diagnostic efficiency higher than the corresponding ULRs.
CONCLUSIONS: Serum LIP and PAMY are specific for the pancreas and might replace total amylase for the diagnosis of acute pancreatitis in hyperamylasemia patients. LIP97.9 is more efficient than PAMY209 in the diagnosis of acute pancreatitis. A combined test of both enzymes is not superior to single test of either enzyme in diagnostic accuracy.