Rapid measurement of insulin using the Abbott IMx: Application to the management of insulinoma

Background: Patients with multiple endocrine neoplasia (type 1) often present with multiple pancreatic endocrine tumours, such as insulinomas. A major difficulty in the surgical treatment of such patients is identifying which tumours are functionally active and therefore need to be resected for a cure. The objective of this study was to develop a rapid insulin assay that could be used intraoperatively for identifying insulinomas from pancreatic aspirates. Methods: By reducing the incubation time and by increasing the sample volume, a rapid insulin assay was developed on the IMx analyser. This was used to measure insulin from tissue aspirates collected from suspected insulinomas under ultrasound guidance. Results: The rapid insulin assay (y) could be performed in 14 min and showed a good correlation with the standard IMx (x) insulin assay (y=0.808x+0.04; r²=0.986). Using the rapid insulin assay on pancreatic tissue aspirates, insulinomas could be readily distinguished from normal pancreatic tissue or from non-functional adenomas based on a marked increase in insulin content. Conclusion: In summary, a new rapid assay for insulin is described that compares favourably to the standard IMx insulin assay and can potentially be used intraoperatively on pancreatic aspirates for identifying functionally active insulinomas.