Evaluating tests for acute pancreatitis

Abstract

The relative merits of various serum pancreatic enzymes, ultrasonography (US), and computerized tomography (CT) have been evaluated. In practice, the diagnosis of acute pancreatitis (AP) remains hinged on the clinical picture and elevated serum amylase. The advantages of total serum amylase are its technical simplicity, ready availability, and sensitivity. Within 24 h of onset of symptoms, elevation of amylase is as sensitive as that of lipase, pancreatic isoamylase, immunoreactive trypsin, or elastase. However, after the first hospital day, it is the least sensitive of the enzymatic tests. Its greatest disadvantage is its overall low specificity. Lipase assays are now fast, reliable, practical, more specific, almost as sensitive, and not more expensive than amylase assays. The current feeling is that lipase assays should be used more often or even should replace amylase assays. However, comparative studies using objective criteria for AP are required to evaluate the utility of lipase estimations over that of amylase. Other enzymes such as P-isoamylase, immunoreactive trypsin, chymotrypsin, or elastase are more cumbersome, expensive, and not better than lipase. They should be reserved for cases of doubtful diagnoses. The levels of these pancreatic enzymes neither correlate with the severity of the disease nor can they accurately predict the subsequent clinical course of the patients. The main role of ultrasonography remains in the evaluation of the biliary tract in AP. The contrast-enhanced computed tomography (CECT) is useful for estimating the presence and extent of pancreatic necrosis. Thereby, it enables prompt recognition of patients at high risk for systemic and local complications. Routine use of CECT may aid in the identification of pancreatitis when enzyme elevations are modest, but the utility of the procedure in all clinically mild cases is questionable. Patients who are seriously ill or who present a diagnostic problem should have a CECT. A normal CT under such circumstances excludes clinically severe AP. Serial CT should be done in patients demonstrating phlegmonous extrapancreatic spread.