Comparison of Disparities between FGM/CGM Sensor Glucose Values and Blood Glucose Values in Type 2 Diabetic Patients Admitted for Glycemic Control

Abstract

Objective: The disparities were compared between flash glucose monitoring (FGM) sensor glucose (SG) values and SMBG blood glucose (BG) values vs. between continuous glucose monitoring (CGM) SG values and BG values to establish the accuracy of FGM SG values. Methods: CGM (CGMS-Gold, Medtronic Minimed) and FGM (FreeStyle Libre Pro; Abbott Japan) were simultaneously put in place in 16 type 2 diabetic patients admitted for glycemic control (BMI, 28.7 ± 5.2 kg/m2; HbA1c, 9.8 ± 2.1%). SMBG BG values at 500 time points registered on CGMS-Gold for calibration purpose and CGM/FGM SG values at the same time points, were selected to examine the accuracy of FGM SG values. Both these devices were evaluated for accuracy in terms of 1) simple correlation coefficients between CGM/FGM SG values and BG values; and 2) mean absolute relative differences (MARD) in SG values of CGM/FGM relative to BG values as reference. Results: 1) A strong positive correlations were found between the SMBG BG values and CGM/FGM SG values (r = 0.9462, p < 0.001 / r = 0.8797, p < 0.001). 2) The MARD in CGM/FGM SG values were 6.53 ± 6.35% (0-47.3%) / 10.35 ± 9.64% (0-65.5%), and the frequency of MARD showing 10% or less accounted for 79.0% of all CGM SG values, and 58.2% of all FGM SG values. The relationship between the MARD in CGM/FGM SG values and the durations of CGM/FGM put in place showed that while the MARD in CGM SG values was nearly constant, the MARD in FGM SG values varied from day to day. Again, the relationship between MARD in CGM/FGM SG values and BG value showed that while the MARD in CGM SG values remained constant, irrespective of BG values, the MARD in FGM SG values tended to increase with decreasing BG values. Additionally, the disparity between the FGM SG values and the BG values varied greatly depending on the individual patient. Conclusions: Despite being an innovative device for glucose monitoring, FGM may be appropriately positioned as an adjunct, but not an alternative, to SMBG. Disclosure M. Tanizawa: None. H. Takahashi: None. Y. Mori: None. K. Utsunomiya: None.