Endocrine Abstracts

Background: The 72-hour fast test remains the gold standard test for endogenous hyperinsulinism during observed prolonged fasting-induced hypoglycaemia. This service evaluation assessed the 72-hour fast test at an ENETS COE between February 2020 and November 2024. The aim was to explore a pre-test tool to select candidates for an observed inpatient 72-hour fast and optimise resource utilisation. We looked specifically at the use of continuous glucose monitoring (CGM) as a potential pre-test tool.

Methods: A retrospective service evaluation project was conducted involving 35 patients who underwent the observed inpatient 72-hour fasts. Data recorded included patient demographics, indication for fasting, use of CGM, occurrence of hypoglycaemic events, final diagnoses, adherence to protocol, documentation of results, and reasons for test termination.

Results: Among the 35 patients, 63% were female and 37% male. Continuous Glucose Monitoring (CGM) was not done in 8 patients out of the whole study population (23% of cases). 7 of these had no significant hypoglycaemia or diagnosed with insulinoma, and 1 confirmed insulinoma recurrence. Among the remaining 27 patients who underwent CGM monitoring (77%), 13 (48%) showed pseudo-hypoglycaemia, 11 (40%) had reactive hypoglycaemia, and only 1 was confirmed to have insulinoma. In addition, one case was attributed to adrenal insufficiency with suboptimal steroid dosing, and another developed hypoglycaemia during steroid weaning (PANDAS syndrome). The 72-hour fast completion rate was 66%, with 34% not completing due to hypoglycaemia (9%), self-discharge (2%), or non-specific symptoms (23%). Documentation quality was suboptimal, with over 70% of cases lacking protocol adherence, although discharge letters were completed for 68.5% of patients. This evaluation highlights that CGM provides valuable information for pre-test stratification. Many patients demonstrated pseudo- or reactive hypoglycaemia, suggesting that prolonged fasting may have been unnecessary for certain cases. Moreover, the adrenal insufficiency cas emphasises the importance of careful clinical assessment and specialist input before fasting test. A larger study is needed to corroborate our findings, but we recommend routine CGM before the 72-hour fast to improve diagnostic accuracy, reduce unnecessary admissions, and enhance patient safety, with fasting protocols restricted to specialist wards supported by trained staff.