Few studies have assessed the accuracy of the FreeStyle Libre Pro (FLP) continuous glucose monitor for estimating plasma glucose (PG) in non-diabetic children. Objective Determine the accuracy of FLP compared to PG during OGTT in healthy children. Subjects Children (7–11.99y) with healthy weight & overweight/obesity (n=33; 52% male). Methods Participants wore the FLP before and during a 2-hour OGTT; PG was measured at 30min intervals. Potential systematic- and magnitude-related biases for FLP vs. PG were examined. Results FLP 15-minute averages and PG were correlated at most timepoints during OGTT (r2=.35-.69, p’s<0.001 for time point 30–120minutes) and for PG area under the curve (AUC) (r2=0.65, p<0.0001). There were no systematic biases as assessed by Bland-Altman analyses for FLP AUC or for FLP at each OGTT timepoint. However, for fasting glucose, a significant magnitude bias was noted (r2=0.38, p<0.001), such that lower PG was underestimated, and higher PG was overestimated by FLP readings; further, there was poor correlation between fasting PG and FLP (r2=0.06, p=0.22). BMIz was also associated with FLP accuracy: FLP overestimated PG in children with low BMIz and underestimated PG in those with overweight/obesity for OGTT AUC and OGTT PG at baseline, 60, and 120 minutes (all p’s≤0.015). No adverse events occurred with FLP. Conclusions Among children without diabetes, the FLP was well tolerated and correlated with post-OGTT glucose, but had magnitude bias affecting fasting glucose and appeared to underestimate plasma glucose in those with overweight/obesity. These results suggest potential limitations for the utility of the FLP for research.

BACKGROUND: Ensuring children are fasting for blood draws is necessary to diagnose abnormalities in glucose homeostasis. We sought to determine if serum free fatty acid (FFA) concentrations might be a useful marker to differentiate the fed and fasted states among children.METHODS: A total of 442 inpatient (fasting) and 323 (postglucose load) oral glucose tolerance test samples of glucose, insulin, and FFA from children (age 5-18 years) who had healthy weight, overweight, or obesity were examined by receiver operating characteristic (ROC) curve analysis to identify a cut point for nonfasting. In a cross-sectional study, we compared mean FFA and percentage of FFA values below this cut point as a function of inpatient (n = 442) versus outpatient (n = 442) setting. RESULTS:The area under the curve of FFA was significantly better (P values , .001) than the area under the curve of glucose or insulin for identifying nonfasting. FFA ,287 mEq/mL had 99.0% sensitivity and 98.0% specificity for nonfasting. Mean FFA was lower in outpatients than inpatients (P , .001); only 1.6% inpatient but 9.7% outpatient FFA values were consistent with nonfasting (P , .001).CONCLUSIONS: Clinicians cannot assume that pediatric patients are adequately fasted on arrival for fasting blood work. On the basis of having significantly lower outpatient than inpatient FFA values and more frequently suppressed FFA, children appeared less likely to be fasting at outpatient appointments. FFA value ,287 mEq/mL was a sensitive and specific cutoff for nonfasting in children that may prove clinically useful.

Objective: To evaluate the accuracy and practicality of the FreeStyle Libre Pro continuous glucose monitor (CGM) during oral glucose tolerance testing (OGTT) in a nondiabetic pediatric sample. Background: The FreeStyle Libre Pro CGM has been found, in adults, to have acceptable accuracy compared to lab-measured glucose without requiring individual patient calibrations. No studies have assessed lab-measured glucose accuracy for this CGM in children. Hypothesis: FreeStyle Libre Pro CGM glucose will not differ significantly from lab-measured plasma glucose during OGTT in youth. Methods: Healthy weight and overweight volunteers (n =8; 63% male), aged 7-11y wore FreeStyle Libre Pro Flash CGM for 6 days, with a 2-hour OGTT (1.75mg/kg, max 75g) on day 6. Laboratory (Cobas E6000, Roche) plasma glucose was measured at 30min intervals for 120min, and compared with the 15min average simultaneously obtained CGM glucose value. Glucose at each timepoint and Area Under the Curve (AUC) for CGM and lab-measured glucose were compared using paired t-tests. A correlation coefficient was calculated for each timepoint. Potential systematic errors were examined using Bland-Altman analyses. Results: AUC for CGM and lab glucose were well correlated (r= 0.91, p=0.006) and did not differ in mean value (p=0.84). CGM and lab glucose readings were not significantly different at any timepoint (all p’s&gt;0.18). There were no significant systematic or magnitude errors as assessed by Bland-Altman analyses at any timepoint. No adverse events occurred with CGM use and all participants considered the device easy to wear. Conclusions: The Freestyle Libre Pro CGM device was well tolerated and, even without individual calibration, provided quantitatively similar glucose readings during OGTT for healthy weight and overweight children when compared to lab-measured glucose. If confirmed in larger studies, this CGM may provide adjunctive data during evaluations of glucose excursions that may be useful for pediatric clinical care and research. Disclosure N. Ghane: None. M. Broadney: None. S.M. Collins: None. E.K. Davis: None. S. Brady: None. J.A. Yanovski: Research Support; Self; Rhythm Pharmaceuticals Inc., Zafgen.