Endocrinol Metab.  2014 Dec;29(4):498-504. 10.3803/EnM.2014.29.4.498.

Clinical Implications of Various Criteria for the Biochemical Diagnosis of Insulinoma

• Ahn CH
• Kim LK
• Lee JE
• Jung CH
• Min SH
• Park KS
• Kim SY
• Cho YM

• KMID: 2384247
• DOI: http://doi.org/10.3803/EnM.2014.29.4.498

Abstract

BACKGROUND
Among the various diagnostic criteria for insulinoma, the ratio criteria have been controversial. However, the amended insulin-glucose ratio exhibited excellent diagnostic performance in a recent retrospective cohort study, although it has not yet been validated in other patient cohorts. We examined the diagnostic performance of the current criteria of the Endocrine Society, insulin-glucose ratio, C-peptide-glucose ratio, and amended ratios in terms of differentiating insulinomas.
METHODS
We reviewed the medical records of patients who underwent evaluation for hypoglycemia from 2000 to 2013. Fourteen patients with histopathologically confirmed insulinoma and 18 patients without clinical evidence of insulinoma were included. The results of a prolonged fast test were analyzed according to the abovementioned criteria.
RESULTS
Fulfilling all three Endocrine Society criteria-plasma levels of glucose (<3.0 mmol/L), insulin (> or =8 pmol/L), and C-peptide (> or =0.2 nmol/L)-exhibited 100% sensitivity and 89% specificity. Fulfilling the glucose and C-peptide criteria showed 100% sensitivity and 83% specificity, while fulfilling the glucose and insulin criteria showed 100% sensitivity and 72% specificity. Among the ratio criteria, the insulin-glucose ratio [>24.0 (pmol/L)/(mmol/L)] gave the highest area under the receiver operating characteristic curve, with 93% sensitivity and 94% specificity.
CONCLUSION
Fulfilling the glucose, insulin, and C-peptide criteria of the Endocrine Society guidelines exhibited the best diagnostic performance for insulinoma. Nonetheless, the insulin-glucose ratio may still have a role in the biochemical diagnosis of insulinoma.

Keyword

Insulinoma; Diagnostic criteria; Insulin; C-peptide

MeSH Terms

C-Peptide
Cohort Studies
Diagnosis*
Glucose
Humans
Hypoglycemia
Insulin
Insulinoma*
Medical Records
Retrospective Studies
ROC Curve
Sensitivity and Specificity
C-Peptide
Glucose
Insulin

Figure

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  Fig. 1 Proportion of patients by time to discontinuation of the prolonged fast test.

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  Fig. 2 Distribution of glucose, insulin, C-peptide, insulin-glucose ratio, C-peptide-glucose ratio, amended insulin-glucose ratio, and amended C-peptide-glucose ratio at discontinuation of the prolonged fast test. Scatter plots show the distributions of plasma glucose (A), insulin (B), C-peptide (C), insulin-glucose ratio (D), amended insulin-glucose ratio (E), C-peptide-glucose ratio (F), and amended C-peptide-glucose ratio (G). Dashed lines indicate the cutoff value from the Endocrine Society Clinical Practice Guidelines (A-C) or the cutoff value showing the highest Youden index in the receiver operating characteristic curve analysis of our current data (D-G). Closed circles, insulinoma; open circles, noninsulinoma.

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