Glucose Management Indicator Based on Sensor Data and Laboratory HbA1c in People With Type 1 Diabetes From the DPV Database: Differences by Sensor Type.

Abstract

The glucose management indicator (GMI) estimates HbA1c from continuous glucose monitoring (CGM) profiles. The formula was developed with real-time CGM (rtCGM) sensors (1). As previous data indicated discrepancies between observed laboratory HbA1c and CGM-derived estimates of HbA1c for some individuals and sensor types (1,2), we aimed to compare observed HbA1c and GMI using both rtCGM and intermittent scanning CGM (iscCGM) profiles collected during routine care in people with type 1 diabetes. We analyzed 132,361 CGM days from a total of 1,973 individuals with type 1 diabetes for ≥1 year from the German/Austrian/Swiss/Luxembourgian Prospective Diabetes Follow-up Registry (DPV) (3). As measurement ranges of the CGM devices differed, we truncated glucose values to the same range (40–400 mg/dL). We calculated the GMI from up to 90 CGM days per individual (median \[interquartile range] 77 [46–89] days per individual) as GMI (%) = 3.31 + 0.02392 ⋅ [mean glucose (mg/dL)\] (1). We compared GMI and observed HbA1c at the end of the 90-day period overall and by age-group. Absolute differences between GMI and observed HbA1c were illustrated for rtCGM vs. iscCGM and stratified by glucose variability, normal weight vs. overweight, and HbA1c 90th percentile for individuals aged 25 kg/m2 …