Assessment of suspected insulinoma by 48-hour fasting test: a retrospective monocentric study of 23 cases.
OBJECTIVE
Insulinoma causes fasting hypoglycaemia due to inappropriate insulin secretion. The diagnosis of insulinoma is based on Whipple's triad during a supervised fasting test. The aim of our study was to evaluate retrospectively the percentage of positive 48-hour fasting tests in a large series of patients with insulinoma.


METHODS
In a retrospective study, we identified 39 patients (24 females, 15 men; average age 47 years [range 12-78 years]) with insulinoma. Sixteen patients were diagnosed by spontaneous hypoglycaemia. Twenty-three patients with insulinoma were tested with a 48-hour fasting test and compared to 31 healthy controls who had a negative fasting test and were followed up for at least two years.


RESULTS
The fast was terminated due to neuroglycopenic symptoms in 4 patients (17.4%) at the 12th hour, in 17 patients (73.9%) at the 24th hour, and in 22 patients (95.7%) at the 48th hour. One patient with insulinoma had no neuroglycopenic symptoms, but was diagnosed by glucose and insulin levels during the 48-hour fast. Healthy controls had significantly higher blood glucose and lower insulin levels, and a lower insulin-glucose ratio than patients with insulinoma at the end of the fast.


CONCLUSIONS
In conclusion, the 48-hour fasting test was successful in the diagnosis of insulinoma in 95.7% of patients. In this series we did not observe a need for fasting beyond 48 hours.
Quinkler
M
M
Clinical Endocrinology, Internal Medicine Center for Gastroenterology, Hepatology, and Endocrinology, Charité Campus Mitte, Charité Universitätsmedizin Berlin, Berlin, Germany. marcus.quinkler@charite.de
Strelow
F
F
Pirlich
M
M
Rohde
W
W
Biering
H
H
Lochs
H
H
Gerl
H
H
Strasburger
C J
CJ
Ventz
M
M
D000293:Adolescent; D000328:Adult; D001786:Blood Glucose; D002648:Child; D003710:Demography; D005215:Fasting / Q000502:physiology*; D005260:Female; D006801:Humans; D007328:Insulin / Q000097:blood; D007340:Insulinoma / Q000175:diagnosis*; D008297:Male; D008875:Middle Aged; D012189:Retrospective Studies
D001786:Blood Glucose; D007328:Insulin