It has become common place for us to compare various patient registries in terms of A1C, rates of DKA, and severe hypoglycemia. We were curious to better understand glucometrics from CGM in the University of Washington Diabetes Care Center.
From March 2017 to November 2019 we reviewed 247 patients with type 1 diabetes using CGM.
Average age was 52 years, average duration of diabetes was 28 years, half were women, and mean A1C was 7.2%. Sixty percent used Dexcom, 29% used Medtronic, and 11% used the Abbott Libre. Mean glucose was 163 mg/dL with a percent coefficient of variation (CV) of 34.8%. TIR for the population was 60.4% with Time Below Range (TBR) of 3.5%. GMI was 7.2%. Using mean glucose to predict GMI, 34% and 7% of measured A1C values were at least 0.5% and 1% discordant respectively.
It is concluded that current consensus guidelines for TIR are reasonable. Percent CV below or equal to 33% is possible in T1D despite arguments this target should be below 36%. Finally, the GMI equation closely approximates our population’s CGM data.