Serum lipase activity is increased in disease states other than acute pancreatitis: amylase revisited.

For more than 50 years, total serum amylase activity has been the biochemical test most commonly used to confirm the clinical diagnosis of acute pancreatitis. Serum amylase activity has been hoisted onto this pedestal by default, because until recently it has been the only reproducible and rapid diagnostic assay available in clinically emergent settings. As a result of our longstanding dependence and need for accurate interpretation of serum amylase values, considerable knowledge has accumulated during the past two decades about pancreatic and nonpancreatic human isoamylases. Their organs of origin, substrate specificity (1), electrophoretic properties (2), and their circulatory clearance and organ metabolism (3, 4) have all been extensively investigated. Moreover, we now know that hyperamylasemia is associated with a wide variety of clinical conditions other than acute pancreatitis (5). Despite its limitations, however, hyperamylasemia has become the biochemical yardstick for confirming the clinical diagnosis of acute pancreatitis against which newer, unproven assays are measured. In this issue of Clinical Chemistry, two articles examine the use of serum lipase activity assayed with Kodak Ektachem technology in diagnosing acute pancreatitis.’ Tetrault reviewed the medical records of >100 patients who had both lipase and amylase assays performed and in whom either lipase or amylase (or both) was increased above the upper reference limit (6). Interestingly, he found that 84% of patients categorized as having abdominal disorders apparently unrelated to the pancreas had hyperlipasemia without an increase in serum amylase activity. Lott and Lu (7) reviewed the charts of their 81 patients and report that lipase has a higher diagnostic efficiency than amylase in acute pancreatitis. They also found, however, that many patients with multisystem disease or acute abdominal processes different from acute pancreatitis have either an abovenormal serum lipase activity or an electrophoretic form of lipase, L2, that apparently is not normally found in serum but can be detected in human pancreatic juice by electrophoresis. Thus, patients without apparent pancreatitis, but with complex processes or other abdominal pathology, often had hyperlipasemia. This group of patients is most challenging for clinicians, because appropriate therapy in such patients often depends on an accurate diagnosis. To the extent (and only to the extent) that the categorization of these patients was correct, the reported observations raise the possibility that, despite its touted specificity, serum lipase activity may not be more specific for pancreatic inflammation