Relationship between HbA1c and the Time in Range Derived from Flash Glucose Monitoring System

  Objective  To explore the relationship between HbA1c and time in range (TIR) derived from flash glucose monitoring system (FGMS) in Chinese adults with type 1 diabetes mellitus (T1DM).

  Methods  Adult T1DM patients attended the outpatient department of Peking Union Medical College Hospital (PUMCH) from October 2018 to March 2019 were included. HbA1c and data of FGMS were obtained at the same time. TIR was calculated, and the relationship between TIR and HbA1c was investigated by Spearman correlation and regression analysis.

  Results  A total of 77 patients who met the inclusion and exclusion criteria were included in the analysis. The average HbA1c was (7.5±1.3)%; TIR was 62.0 (48.7, 67.8)% and coefficient of variation(CV) was (39.7±8.1)%. TIR derived from FGMS had a negative liner correlation with HbA1c (r=-0.645, P < 0.001). The regression equation is: HbA1c=10.58-0.05×TIR. The HbA1c level is decreased by 0.5% for every 10% increase in TIR. TIR was negatively correlated with HbA1c in patients with both stable glucose (CV < 36%) and unstable glucose (CV≥36%), but the correlation coefficient between TIR and HbA1c in patients with stable glucose was higher. For a specific TIR, HbA1c was higher in patients with stable glucose.

  Conclusion  The FGMS-derived TIR could be helpful in the glucose management in Chinese adults with T1DM, and glucose variability should be taken into consideration while interpreting the relationship between TIR and HbA1c.