Within-Person and Between-Sensor Variability in Continuous Glucose Monitoring Metrics

BACKGROUND: The within-person and between-sensor variability of metrics from different interstitial continuous glucose monitoring (CGM) sensors in adults with type 2 diabetes not taking insulin is unclear. METHODS: Secondary analysis of data from 172 participants from the Hyperglycemic Profiles in Obstructive Sleep Apnea randomized clinical trial. Participants simultaneously wore Dexcom G4 and Abbott Libre Pro CGM sensors for up to 2 weeks at baseline and again at the 3-month follow-up visit. RESULTS: At baseline (up to 2 weeks of CGM), mean glucose for both the Abbott and Dexcom sensors was approximately 150 mg/dL (8.3 mmol/L) and time in range (70-180 mg/dL [3.9-10.0 mmol/L]) was just below 80%. When comparing the same sensor at 2 different time points (two 2-week periods, 3 months apart), the within-person coefficient of variation (CVw) in mean glucose was 17.4% (Abbott) and 14.2% (Dexcom). CVw for percent time in range: 20.1% (Abbott) and 18.6% (Dexcom). At baseline, the Pearson correlation of mean glucose from the 2 sensors worn simultaneously was r = 0.86, root mean squared error (RMSE), 13 mg/dL (0.7 mmol/L); for time in range, r = 0.88, RMSE, 8 percentage points. CONCLUSIONS: Substantial variation was observed within sensors over time and across 2 different sensors worn simultaneously on the same individuals. Clinicians should be aware of this variability when using CGM technology to make clinical decisions.