Evaluation of a specific immunoinhibition method for the determination of pancreatic alpha-amylase.

Ten clinical centres in Italy participated in an evaluation of a pancreas-specific alpha-amylase assay using two monoclonal antibodies. Comparisons with electrophoretic methods showed good agreement in the reference range, but systematic deviations above it. The diagnostic information of the two methods appeared substantially different if the percentage values from electrophoresis were compared with activity units from the immunoinhibition method, but became similar if the two methods were compared on the basis of activity units. Reference intervals determined for serum/plasma corresponded to those previously published, but those determined for urine differed slightly from the published values. Clinical sensitivities for the assessment of acute pancreatitis (n = 134) were found as follows. Related to the upper limit of the control group (n = 141), the pancreatic alpha-amylase, total alpha-amylase and lipase showed sensitivities of 0.94, 0.87 and 0.93, respectively. When the cut-off point was set at the three-fold upper limit of the control group, sensitivities of 0.73, 0.53 and 0.70 were found, and the specificity was 1.00 for all three methods. Based on this commonly used higher cut-off point, the determination of lipase in addition to pancreatic alpha-amylase enhanced the sensitivity in the recognition of acute pancreatitis by 8%; conversely, the determination of pancreatic alpha-amylase in addition to lipase increased the number of true positive results by 13%. The high practicability and interlaboratory transferability documented in the results of the collaborative study show that the pancreatic alpha-amylase assay is very useful for recognizing pancreatic inflammations, especially in combination with lipase.