Use of continuous glucose monitoring evaluating the accuracy and the effect on metabolic parameters in patients with gsd i followed at GaziUuniversity hospital pediatric metabolic unit

Introduction: Glycogen storage disease type I (GSD I) is characterized by impaired production of glucose from glycogenolysis and gluconeogenesis, results from defects in the glucose 6-phosphate enzyme system. Glucose-6-phosphatase is affected in GSD Ia, whereas GSD I non-a results from a defect of the G6P transporter, G6P translocase. Type Ia involves the liver, kidney and intestine (and Ib also leucocytes), and the clinical manifestations are hepatomegaly, failure to thrive, severe fasting hypoglycemia within 3-4 h after a meal, hyperlactatemia, hyperuricemia and hyperlipidemia. The aim of the present study was to examine the efficacy of a continuous subcutaneous glucose monitoring system, to determine the magnitude and significance of hypoglycemia in patients with GSD I and to evaluate the efficacy of the revised dietary treatment.Material-Method: Medtronic real time continuous glucose monitoring device was used in the current study. Sixteen children (9 boys and 7 girls) with GSD I were studied over a 72-h period. We have investigated 15 patients with GSD Ia, one patient with GSD Ib with continuous glucose monitoring. The patients and doctors were not aware of the sensor recordings during the time of glucose monitoring. Capillary blood glucose was measured several times before meals and snacks during this time by the parents or doctors using a glucometer which reliably detects blood samples. More uncooked cornstarch was added to the diet of patients and glucose intake was increased according to first CGM glucose concentrations, and altered the time interval between meals. CGM was repeated 3 to 6 months after the first monitoring in all patients to examine the effects of revised dietary instructions on glycemic control. Statistical analyses were performed using the SPSS software version 11,5. The variables were investigated using visual (histogramas, probability plots) and analytical methods (Kolmogorov-Smirnov/Shapiro-Wilk's test) to determine whether or not they are normally distributed. While investigating the associations between non-normally distributed and/or ordinal variables, the correlation coefficients and their significance were calculated using the Pearson test. All tests were considered significant for p values <0.05.Results: Mean age of the study population was 7.59± 4.12 years (range 2-18). During the study, the patients followed a normo-caloric diet suggested by the registered dietician with a distribution of nutrients as recommended for patients with GSD I (57-64 % carbohydrates, 25-29 %lipids, 10-16 %proteins). All the patients completed the study without any major adverse events. Significant periods of asymptomatic hypoglycemia (below 4 mmol/L, 70 mg/dl) were noted. There was a close correlation between CGM sensor and capillary blood glucose values measured by glucometer. The correlation coefficient between glucose values obtained with medtronic real time continuous glucose monitoring device and capillary measurements was 0,86 (r2=0,74) before and 0.77 (r2=0.65) after the diet was modified. CGM indicated a considerable reduction in liver size and duration of hypoglycemia which dropped from 7.06±5.04 % to 2.25±2.79% (p=0.002), and improvements in secondary metabolic derangements such as hyperlacticacidemia, hypertriglyceridemia, AST and ALT levels.Discussion: Real time glucose monitoring device provides glucose measurements every 1-5 minutes, producing 288 measurements per day, consists of a disposable transcutaneous glucose sensor connected to a transmitter and a receiver. The receiver has a screen that displays the glucose level together with graphic representations of the glucose patterns. Medtronic real time continuous glucose monitoring device also has adjustable alarms for high and low glucose levels. The system is calibrated using finger stick blood glucose measurements. From our experience CGM, in combination with other appropriate biochemical monitoring and dietary intake records has been shown to be a useful tool in the practical management of GSD.Key words: Continuous Glucose Monitoring, GSD type I, Children