Differences in glucose readings between the continuous glucose monitoring calibration free interstitial sensors versus capillary blood glucose monitoring by glucometer: An analysis of two cases.

Aim: To assess the differences in glucose readings between the continuous glucose monitoring calibration-free interstitial sensors versus capillary blood glucose monitoring by glucometer.

Study Design: Two healthy non-pregnant volunteers participated in the study, and wore simultaneously both the calibration-free Freestyle Libre and the Dexcom G6 sensor. Glucose values were recorded before and after meals during breakfast, lunch, and dinner on three separate days by either scanning the Freestyle Libre CGM sensor with a smartphone, or obtaining glucose readings real-time through the Dexcom G6 CLARITY mobile application. Blood glucose values were recorded using the Accu-Chek Active glucose meter. The Wilcoxon signed-rank test was used for paired non-parametric data to compare glucose readings between groups.

Results: The average glucose values obtained from the Dexcom G6 CGM consistently registered higher (6.54 ± 0.80 mmol/L) and those from the Freestyle Libre (5.49 ± 0.65 mmol/L) consistently lower, from the glucometer (6.17 ± 0.55 mmol/L), with p-value <0.05 between groups. In the three-way comparison, the Dexcom G6 CGM sensor yielded the highest values, followed by the glucose meter, and finally the Freestyle Libre CGM sensor.

Conclusion: Both CGM systems exhibited discrepancies from blood glucose (BG) measurements, and variations were observed among the different CGM systems themselves.