An Exploratory Analysis of Continuous Glucose Monitoring Metrics in Relation to Prediabetes in Youths with Obesity

<b><i>Introduction:</i></b> Youth obesity is a strong risk factor for prediabetes (PD) and type 2 diabetes. Current criteria for the diagnosis of PD/diabetes, including fasting glucose, 2-h blood glucose after oral glucose tolerance test (OGTT), and HbA1c, have some acknowledged limitations in youth. Continuous glucose monitoring (CGM) offers the opportunity to record daily glucose profiles in a free-living conditions. This study aims to explore how the CGM metrics are related to PD in youths with obesity. <b><i>Method:</i></b> Youths with obesity (BMI-for-age > 2SD, age 10-18 years) wore a Freestyle Libre 2 CGM sensor for 2 weeks. Several CGM metrics were measured, including time in tight ranges (TITR) 70-140 and 70-120 mg/dL. All subjects underwent OGTT, and normal glucose tolerance (NGT) and prediabetes (PD) were defined by American Diabetes Association criteria. A nonparametric Wilcoxon rank-sum test was used to compare NGT and PD youths, and logistic regression analysis was performed to investigate the ability of CGM metrics to predict PD. <b><i>Results:</i></b> Overall, 84 youths (age 12.6 ± 1.9 years, 42.4% female, BMI 32.8 ± 6.6 kg/m², HbA1c5.4 ± 0.2%, CGM use >80%) were recruited. HbA1c, blood glucose measured at baseline, 30, 90, and 120 min, and the area under the curve of glucose after glucose load were significantly higher (<i>P</i> value <0.05) in PD than in NGT youths. TITR 70-140 mg/dL and TITR 70-120 mg/dL were significantly (<i>P</i> < 0.05) lower in PD than in NGT youths. No other CGM metrics differed between the two groups. Both TITR 70-140 and 70-120 mg/dL significantly predict PD (<i>P</i> = 0.02), independent of age and sex, though with modest discriminative ability. <b><i>Conclusions:</i></b> This exploratory study showed that TITR measured in free-living may aid the identification of PD in youths with obesity, although the discriminative ability of CGM metrics was limited. Future works will focus on the analysis of the concordance of plasma glucose and CGM during OGTT, as well as their predictive performance.