2937-LB: Agreement of Continuous Glucose Monitoring during Oral Glucose and Mixed-Meal Tests

Introduction and Objective: Continuous Glucose Monitoring (CGM) is widely used for glycemic management in type 2 diabetes and increasingly used in persons at risk for diabetes. CGM-derived glucose estimates may differ by up to 15% from venous plasma glucose, and performance in youth-onset type 2 diabetes (Y-T2DM), particularly during rapid glucose excursions, is not well characterized. We evaluated agreement between CGM and plasma glucose-derived metrics during an oral glucose tolerance test (OGTT) and mixed meal test (MMT) using glucose area under the curve (AUC) and model-derived disposition index without insulin (mDI-woI). Methods: This interim analysis included 24 Y-T2DM and 9 healthy controls who underwent a 120-minute 75g OGTT and 300-minute liquid MMT. CGM (Dexcom G7) was worn during testing. Glucose AUC was calculated using the trapezoidal rule. mDI-woI, an integrated measure of β-cell function, was derived by fitting OGTT data to an insulin sensitivity and secretion model in MATLAB. Statistical analyses included Welch’s t-test, Bland-Altman analysis and Lin’s Concordance Correlation Coefficient in R. Results: Participants were 20±3 years old (mean±SD), 52% female, BMI 36.3±11.0 kg/m2, and HbA1c 6.8±2.5%. Y-T2DM had higher BMI and HbA1c than controls (P0.05). CGM AUC exceeded plasma AUC during OGTT (mean 95% CI bias 2446 1017, 3875 mg/dL·120 min, P0.01) and MMT (3524 1073, 5974 mg/dL·300 min, P0.01). AUC bias did not differ between Y-T2D and controls for OGTT and MMT (P0.05). Concordance between CGM and plasma AUC was lower for OGTT (r=0.78) than MMT (r=0.93). mDI-woI estimates were lower using CGM versus plasma glucose (bias: -0.19 -0.27, -0.10 10-4 mL/mU/min) with poor concordance (r=0.46). Conclusion: During standardized metabolic testing, CGM-derived metrics overestimated glucose relative to plasma. Concordance varied by physiological context and was lower for OGTT-derived measures than MMT. Poor agreement highlights important limitations of CGM-derived metrics for modeling glucose dynamics and diabetes risk in youth. Disclosure N. Sala: None. M.M. Gaydos: None. I.N. Kacker: None. N.A. Macheret: None. S.L. Cantor: None. A. Sherman: None. J. Ha: None. N. Rangos: None. L. Mabundo: None. N. Malandrino: None. S. Chung: None. Funding National Institute of Diabetes & Digestive & Kidney Diseases, Z99 DK 999999