Use of Flash Glucose Monitoring and Glycemic Control in Patients with Type 2 Diabetes Mellitus Not Treated with an Intensive Insulin Regimen: 1-Year Real-Life Retrospective Cohort Study.

Introduction: Estimation of laboratory-derived glycated hemoglobin (HbA1c) cannot be individually used to monitor clinically significant trends in glucose variability. Hence, clinicians advise use of continuous glucose monitoring (CGM) devices such as the Freestyle Libre™ flash glucose monitoring system (FLASH) to optimize glycemic control by estimating glucose monitoring index (GMI) values, which convert mean glucose into an estimate of simultaneously measured laboratory HbA1c. This study aimed to investigate the sustainability of intermittently scanned continuous glucose monitoring (isCGM) in patients with type 2 diabetes mellitus (T2DM) not on intensive insulin regimen, and correlations between GMI values obtained from isCGM and laboratory-derived HbA1c values.

Methods: A retrospective review of 93 patients with T2DM not on intensive insulin regimen, using FLASH device, was conducted at a major tertiary hospital in Saudi Arabia, over 1 year of continuous device use. To determine the sustainability of isCGM, various glycemic markers such as average glucose and time in range were evaluated. Paired t test or Wilcoxon signed-rank test was used to assess differences in markers of glycemic control, and Pearson's correlation was used to determine correlations between HbA1c and GMI values.

Results: Descriptive analysis shows the mean HbA1c value significantly decreased following continued use of isCGM. Pre-isCGM mean HbA1c value of 8.3% improved to 8.1% (p < 0.001) and 7.9% (p < 0.001) in the first 90 and last 90 days of device use, respectively. For both 90-day time periods, correlation analysis revealed a statistically significant positive correlation and linear regression between laboratory-derived HbA1c and GMI values (first 90 days r = 0.7999, p < 0.001; last 90 days r = 0.6651, p < 0.001).

Conclusion: Continuous use of isCGM demonstrated reductions in HbA1c levels for patients with T2DM not on an intensive insulin regimen. The GMI values showed high levels of agreement with measured HbA1c, indicating their accuracy in glucose management.