Diagnostic accuracy of an "amended" insulin-glucose ratio for the biochemical diagnosis of insulinomas.

Publisher: American College of Physicians--American Society of Internal Medicine Country of Publication: United States NLM ID: 0372351 Publication Model: Print Cited Medium: Internet ISSN: 1539-3704 (Electronic) Linking ISSN: 00034819 NLM ISO Abbreviation: Ann Intern Med Subsets: MEDLINE

Publication: <2001->: Philadelphia, PA : American College of Physicians--American Society of Internal Medicine
Original Publication: Philadelphia [etc.] American College of Physicians.

Blood Glucose/*metabolism ; Insulin/*blood ; Insulinoma/*diagnosis ; Pancreatic Neoplasms/*diagnosis; Adult ; Aged ; C-Peptide/blood ; Fasting ; Female ; Glucose Tolerance Test ; Humans ; Hypoglycemia/etiology ; Insulin/metabolism ; Insulin Secretion ; Insulinoma/blood ; Insulinoma/complications ; Male ; Middle Aged ; Pancreatic Neoplasms/blood ; Pancreatic Neoplasms/complications ; Practice Guidelines as Topic ; Predictive Value of Tests ; Radioimmunoassay ; Retrospective Studies

Background: Recent biochemical diagnostic guidelines for insulinomas require demonstration of hypoglycemia with inappropriately elevated (nonsuppressed) insulin, C-peptide, or proinsulin, but these criteria may overlap with those in patients without insulinomas. Use of an "amended" insulin-glucose ratio that accounts for the normal variation in insulin secretion according to prevailing glycemia may improve diagnostic accuracy.
Objective: To compare the diagnostic accuracy of current diagnostic guideline criteria with the amended insulin-glucose ratio in patients with a suspected insulinoma.
Design: Retrospective cohort study.
Setting: 2 specialized university departments in Germany.
Patients: 114 patients with suspected hypoglycemia over 10 years having diagnostic prolonged fasts.
Measurements: Glucose, insulin, C-peptide, and the amended insulin-glucose ratio were measured during and at discontinuation of prolonged fasts.
Results: Of 114 patients who were evaluated, 49 had surgical resection of histologically confirmed insulinomas. Insulinoma was excluded in 65 patients; follow-up for a mean of 10 years (range, 0 to 16 years) showed no progressively severe hypoglycemic events or diagnoses of insulinoma. Patients with insulinoma had lower glucose levels and higher insulin and C-peptide levels overall than did control patients at the end of prolonged fasts, but there was considerable overlap. The amended insulin-glucose ratio correctly identified 48 of 49 patients with insulinoma and excluded the diagnosis in 64 of 65 control patients, resulting in positive and negative predictive values of 0.98 (95% CI, 0.89 to 1.00) and 0.99 (CI, 0.92 to 1.00), respectively, compared with 0.75 (CI, 0.63 to 0.85) and 0.98 (CI, 0.89 to 1.00), respectively, for glucose, insulin, and C-peptide concentration criteria.
Limitation: The study had a retrospective design, no proinsulin concentrations were available, and a nonspecific insulin immunoassay (crossreactive with proinsulin) was used.
Conclusion: The amended insulin-glucose ratio showed improved diagnostic accuracy over established criteria that use glucose, insulin, and C-peptide concentrations.
Primary Funding Source: None.

Comment in: Ann Intern Med. 2013 Mar 19;158(6):500-1. (PMID: 23552360)
Comment in: Ann Intern Med. 2013 Mar 19;158(6):501-2. (PMID: 23552391)

0 (Blood Glucose)
0 (C-Peptide)
0 (Insulin)

Date Created: 20121205 Date Completed: 20130208 Latest Revision: 20220311

20221213

10.7326/0003-4819-157-11-201212040-00004

23208166