Blake Cooper, United States of America
Retina Associates OphthalmologyPresenter of 1 Presentation
GLUCOSE MANAGEMENT INDICATOR (GMI) VARIABLY PREDICTS AVERAGE HBA1C LEVELS ACCORDING TO GLYCEMIC VARIABILITY (%CV) ACROSS THE LIFESPAN IN TYPE 1 DIABETES (T1D)
Abstract
Background and Aims
Background and Aims: GMI can estimate average HbA1c based on the mean glucose from at least 14 days of CGM data. Using CGM data, one can also assess glycemic variability with coefficient of variation for glucose (CV, glucose SD/mean x 100%). Given that glycemic levels fluctuate across the lifespan, we aimed to evaluate the accuracy of GMI in estimating average A1c based on CV and age.
Methods
Methods: GMI was calculated from over 300 hours of baseline, masked CGM data collected before starting RT-CGM in 3 US studies in persons with T1D (SENCE [N=143, 2-6y] / CITY [N=152, 14-24y] / WISDM [N=203, 60-86y]). GMI (%) was calculated using the formula: 3.31 + 0.02392 x [mean glucose in mg/dL]. We assessed associations between baseline HbA1c, from a central laboratory, and CGM metrics (mean glucose, TIR (70-180mg/dL) by study and stratified by CV (≤36,>36).
Results
Results: Across all studies, lab HbA1c was strongly correlated with CGM metrics (p<0.0001). When CV>36 vs. CV≤36, GMI underestimated average HbA1c in all studies; greatest differences were seen in adolescents/young adults (CITY). Correlations between HbA1c and mean glucose and TIR were stronger when CV>36 (Table).
Conclusions
Conclusions: These 3 studies affirm that CGM metrics, both mean glucose and TIR, can estimate laboratory HbA1c. Notably, glycemic variability (CV) alters these associations across the lifespan in persons with T1D. Caution should be used in interpreting GMI in those with high variability due to risk for under-approximation; changes in RBC kinetics likely also impact these associations.