title: Clinical implications of various criteria for the biochemical diagnosis of insulinoma.
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 (≥8 pmol/L), and C-peptide (≥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.
  
  
  CONCLUSIONS
  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.
authors.affiliation: Department of Internal Medicine, Seoul National University College of Medicine, Seoul, Korea.
authors.forename: Chang Ho
authors.initials: CH
authors.lastname: Ahn
authors.affiliation: Department of Internal Medicine, Seoul National University College of Medicine, Seoul, Korea.
authors.forename: Lee Kyung
authors.initials: LK
authors.lastname: Kim
authors.affiliation: Department of Internal Medicine, Seoul National University College of Medicine, Seoul, Korea.
authors.forename: Jie Eun
authors.initials: JE
authors.lastname: Lee
authors.affiliation: Department of Internal Medicine, Seoul National University College of Medicine, Seoul, Korea.
authors.forename: Chan Hyeon
authors.initials: CH
authors.lastname: Jung
authors.affiliation: Department of Internal Medicine, Seoul National University College of Medicine, Seoul, Korea.
authors.forename: Se Hee
authors.initials: SH
authors.lastname: Min
authors.affiliation: Department of Internal Medicine, Seoul National University College of Medicine, Seoul, Korea.
authors.forename: Kyong Soo
authors.initials: KS
authors.lastname: Park
authors.affiliation: Department of Internal Medicine, Seoul National University College of Medicine, Seoul, Korea.
authors.forename: Seong Yeon
authors.initials: SY
authors.lastname: Kim
authors.affiliation: Department of Internal Medicine, Seoul National University College of Medicine, Seoul, Korea. ymchomd@snu.ac.kr.
authors.forename: Young Min
authors.initials: YM
authors.lastname: Cho
keywords: C-peptide; Diagnostic criteria; Insulin; Insulinoma