The relative sensitivity of serum lipase versus amylase for radiological image-positive pancreatitis

Background

Due to the absence of a 'gold standard' test for the diagnosis of pancreatitis, the sensitivities of pancreatic enzyme tests for pancreatitis are still debated. We compared the relative sensitivities of lipase and amylase at their upper limit of normal values for image-positive pancreatitis in a large consecutive series of patients who had simultaneous tests of amylase and lipase.

Methods

Consecutive patients with a clinical diagnosis of pancreatitis defined by constant epigastric pain and elevation of the amylase or lipase to greater than 106 U/l or 59 U/l, respectively, were imaged by abdominal sonography or computerized axial tomography (CAT) scan. All included patients had positive radiological evidence of acute pancreatitis.

Results

The pancreas was visualized in 399/473 (84%) patients with suspected pancreatitis and 127/399 (38%) had radiological evidence of pancreatitis. Elevation of the lipase to >59 U/l detected 127/127 cases of image-positive pancreatitis, while elevation of the amylase to >106 U/l detected 113/127 cases (88% sensitive (0.82–0.94)). All cases of acute biliary pancreatitis were detected by both the lipase and amylase. The amylase missed 14 of 65 patients with nonbiliary etiologies of pancreatitis. Four of these were alcoholics.

Conclusion

Our study shows a high degree of relative sensitivity of the lipase compared with amylase for pancreatic injury that is demonstrable on CAT or sonographic imaging. Our findings demonstrate a relative lack of sensitivity of amylase for nonbiliary etiologies of pancreatitis. We recognize that the absolute sensitivity of lipase for image-positive pancreatitis cannot be determined by this retrospective methodology that required elevation of one marker for inclusion.