Using the Secretion Ratios of Insulin and C-peptide During the 2-h Oral Glucose Tolerance Test to Diagnose Insulinoma
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ORIGINAL ARTICLE
Using the Secretion Ratios of Insulin and C‑peptide During the 2‑h Oral Glucose Tolerance Test to Diagnose Insulinoma Jing Liao1 · Fei Ding1 · Wei Luo2 · Xin Nie1 · Yong He1 · Guixing Li1 Received: 5 February 2020 / Accepted: 30 May 2020 © Springer Science+Business Media, LLC, part of Springer Nature 2020
Abstract Background Insulinoma, owing to the low incidence and small volume of the tumor, is often undiagnosed. The 72-h fast test is centered on diagnosing insulinoma; however, it cannot be performed on outpatients. Our aim was to evaluate the results of a 3-h oral glucose tolerance test (3-h OGTT) for insulinoma diagnosis. Methods Thirty-seven patients with insulinoma were enrolled for comparison with 42 control subjects. All patients underwent 3-h OGTT with measurements of insulin and C-peptide. The secretion ratios of insulin and C-peptide at 1, 2, and 3 h were calculated by comparison with their values at 0 h. We used logistic regression analysis to establish the predictive models and compared the diagnostic efficiency by receiver operating characteristic analysis. Results The fasting insulin and C-peptide levels of insulinoma patients were both higher; however, the concentrations at 1 h and 2 h were both lower (P 0.05). Our final logistic regression model was constructed as follows: logit (P) = 8.305 − 0.441 × insulin 2 h/0 h ratio − 1.679 × C-peptide 1 h/0 h ratio. A cutoff value of > 0.351 showed the highest diagnostic accuracy, with an area under the curve of 0.97, a sensitivity of 86.5%, and a specificity of 95.2%. Conclusions The 2-h/0-h insulin ratio, as well as the 1-h/0-h C-peptide ratio, has high diagnostic efficiency for insulinoma. The 2-h OGTT can be an alternative test for diagnosing insulinoma in outpatient settings. Keywords Insulinoma · Hypoglycemia · Insulin · C-peptide · 2-h OGTT
Introduction Insulinoma is one of the pancreatic neuroendocrine tumors and originates from pancreatic beta cells [1, 2]. The incidence is very low, at only approximately 4 cases per 1 million persons per year [3]. Most insulinomas are benign [4], while approximately 5–10% of insulinomas are malignant with distant metastasis at diagnosis [5]. The main manifestation of insulinoma is hypoglycemia, which is defined Electronic supplementary material The online version of this article (https://doi.org/10.1007/s10620-020-06379-z) contains supplementary material, which is available to authorized users. * Guixing Li [email protected] 1
Department of Laboratory Medicine, West China Hospital of Sichuan University, 37 Guoxue Xiang, Chengdu 610041, Sichuan, China
Department of Laboratory Medicine, Peking Union Medical College Hospital, Beijing, China
2
as plasma glucose concentration 0.05). ROC receiver operating characteristic, AUC the area under the curve, 95% CI 95% confidence interval
durations. There were no significant differences among the three indicators (P > 0.05). Figure 3 shows the ROC curves of the three models that had larger AUCs.
Diagnostic Accuracy of Previous Cri
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