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Using the Secretion Ratios of Insulin and C-peptide During the 2-h Oral Glucose Tolerance Test to Diagnose Insulinoma.

Authors
  • Liao, Jing1
  • Ding, Fei1
  • Luo, Wei2
  • Nie, Xin1
  • He, Yong1
  • Li, Guixing3
  • 1 Department of Laboratory Medicine, West China Hospital of Sichuan University, 37 Guoxue Xiang, Chengdu, 610041, Sichuan, China. , (China)
  • 2 Department of Laboratory Medicine, Peking Union Medical College Hospital, Beijing, China. , (China)
  • 3 Department of Laboratory Medicine, West China Hospital of Sichuan University, 37 Guoxue Xiang, Chengdu, 610041, Sichuan, China. [email protected] , (China)
Type
Published Article
Journal
Digestive Diseases and Sciences
Publisher
Springer-Verlag
Publication Date
May 01, 2021
Volume
66
Issue
5
Pages
1533–1539
Identifiers
DOI: 10.1007/s10620-020-06379-z
PMID: 32529519
Source
Medline
Keywords
Language
English
License
Unknown

Abstract

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. 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. 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). The levels at 3 h were not significantly different (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%. 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.

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