Endocrine Abstracts

Introduction: tests alternative to the fasting test are necessary for the diagnosis of numerous causes of non-diabetic hypoglycaemia (NDH), that not provoked by starvation (postprandial hypoglycemia), such as insulin autoimmune syndrome (IAS) and noninsulinoma pancreatogenous hypoglycemia syndrome (NIPHS). However, there is no consensus on the most optimal test (prolonged oral glucose tolerance test (pOGTT) or mixed meal test (MMT)) in this cohort of patients.

Objectives: 1)To determine the accuracy of pOGTT and MMT in the diagnosis of postprandial NDH. 2)To compare the glycemic curves during pOGTT in patients with IAS and NIPHS.

Methods: We included152 patients aged 18-74 years: with IAS (n= 14), NIPHS (n= 9), fasting NDH (n= 108) and without NDH (n= 21). All patients underwent pOGTT and MMT. During pOGTT the analysis of venous blood for glucose was performed at baseline, 120 minutes after a 75 g oral dextrose load, and then every 30 minutes until reaching 6 h, if hypoglycemia in venous blood has not been previously recorded. During the MMT the analysis of venous blood for glucose was performed at baseline, and then every 30 minutes after a mixed meal (containing 36.8 g of carbohydrates, 12 g of proteins, 11.6 g of fats (calorie content - 300 kcal)) oral load until reaching 5 h, if hypoglycemia in venous blood has not been previously recorded. During both pOGTT and MMT, analysis of insulin and C-peptide levels was performed once in a blood sample with diagnosed hypoglycemia.

Results: 1)Sensitivity, specificity, AUC of the pOGTT were: 100,0% [82,7%; 100,0%]; 61,1% [44,8%; 75,2%]; 80,6% [72,5%; 88,6%], respectively. Sensitivity, specificity, AUC of the MMT were: 22,2% [5,7%; 55,9%]; 77,4% [67,2%; 85,0%]; 49,8% [34,7%; 64,9%], respectively. When comparing the AUCs of pOGTT and MMT the significant difference was found, P<0.001. 2)The minimal level of glycemia in patients with IAS and true positive result of pOGTT (2,84 [2,60; 2,93] mmol/l) and in patients with NIPHS and true positive result of pOGTT (2,52 [2,15; 2,63] mmol/l) didn’t differ significantly, р=0,130. Patients with IAS developed hypoglycemia at the 180-300 minutes after beginning of the pOGTT, and patients with the NIPHS developed hypoglycemia at the 120-180 minutes after beginning of the pOGTT.

Conclusion: 1)Patients with suspected NDH should undergo 5-hour pOGTT for the purpose of postprandial hypoglycemia excluding. 2)Patients with NIPHS develop postprandial hypoglycemia earlier, than patients with IAS.