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

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). 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%.

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.

• Authors: Jing Liao, Fei Ding, Wei Luo, Xin Nie, Yong He, Guixing Li
• Journal: Digestive diseases and sciences (Dig Dis Sci) Vol. 66 Issue 5 Pg. 1533-1539 (05 2021) ISSN: 1573-2568 [Electronic] United States
• PMID: 32529519 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)

Chemical References

• C-Peptide
• Insulin

Topics

• Adult
• Aged
• Ambulatory Care
• C-Peptide (blood)
• Female
• Glucose Tolerance Test
• Humans
• Insulin (blood)
• Insulinoma (blood, diagnosis, therapy)
• Male
• Middle Aged
• Pancreatic Neoplasms (blood, diagnosis, therapy)
• Predictive Value of Tests
• Reproducibility of Results
• Retrospective Studies
• Secretory Pathway
• Time Factors