Continuous glucose monitoring in the ruling out recurrent insulinoma

BACKGROUND: Currently, an annual study of venous glucose after night fasting is carried out to detect hypoglycemia for diagnosis the recurrence of insulinoma. However, hypoglycemia cannot always be achieved after night fasting if tumor is small. Previously continuous glucose monitoring (CGM) in diagnosis of recurrence of insulinoma was evaluated in small samples.AIM: To evaluate the effectiveness of CGM in interstitium for the diagnosis of recurrent insulinoma (hypoglycemia) after surgery.METHODS: Adult patients who underwent surgery for insulinoma and with remission in the early postoperative period were included. The glucose level in the interstitium was studied by CGM for a maximum of 14 days, and a single venous blood glucose test was performed after a night fasting. If hypoglycemia was detected by any method, a long-term fasting test to confirm the recurrence of hypoglycemic syndrome and imaging diagnostics to identify insulinoma were performed.RESULT: The study included 29 patients after surgical treatment of insulinoma 3-69 months ago. Normoglycemia was determined in 28 patients after night fasting, while one had hypoglycemia, subsequently confirmed by a long-term fasting test. During the CGM, 25 patients had normoglycemia throughout the entire study period, while hypoglycemia was detected in 4 patients, and among them subsequent long-term fasting test confirmed it in three cases. During instrumental examination, pancreatic formation, different in location from the primary tumor, was detected in these three patients. Thus, the sensitivity of CGM relative to reference night fasting test is 100%, 95% CI (3%; 100%), specificity 89% (72%; 98%), positive predictive value 25% (1%; 81%), negative predictive value 100% (86%; 100%). During CGM no adverse events were detected.CONCLUSIONS: CGM can be used effectively and safely to rule out hypoglycemia; and positive cases require subsequent long-term fasting test.