608-P: Relationship Between Time-in-Range and Estimated HbA1c Derived from Continuous Glucose Monitoring System in Adults with Type 1 Diabetes Mellitus

Aims: Time-in-range (TIR) and estimated glycated hemoglobin (eHbA1c), two key metrics derived from continuous glucose monitoring system (CGMS), are valuable for glycemic control. This study is to investigate the relationship between TIR and eHbA1c, and the impact of glycemic variability on their relationship. Methods: The CGMS data were collected from baseline and follow-up visits in a clinical trial (NCT03522870) and yearly visits in the Guangdong Type 1 Diabetes Translational Medicine Study. Adult patients with type 1 diabetes (≥18 yrs) who had available CGM data for > 3 days were included. Correlation between TIR and eHbA1c was explored according to different stratification of glycemic variability assessed by glucose coefficient of variation (CV). Predicted TIR in the fixed eHbA1c value was calculated via the linear regression equations performed in the respective interquartile group of CV. Results: From March 2014 to July 2020, a total of 260 CGMS data were collected. The mean wearing time of available CGM data was 11.8±3.8 days, and the mean value of TIR, eHbA1c, and CV was 62.9±14.1%, 7.2±0.8%, and 39.4±8.1%, respectively. There was a strong negative correlation between TIR and eHbA1c (R=-0.83, P<0.001). For patients with stable glycemic variability (CV<36%), the correlation between the two metrics was stronger (R=-0.95) while in the unstable group the coefficient was decreased (R=-0.80). Based on the regression equations, the predicted %TIR value was decreased across the ascending quartiles with 73.0% in the lowest quartile of CV (<25th quartile, <33.8%), 67.4% in 25th - 50th quartile (33.8-39.2%), 61.4% in 50th - 75th quartile (39.2-44.9%) and 58.5% in the highest quartile (>75th quartile, CV >44.9%) when eHbA1c was set as 7%. Conclusions: There is a strong correlation between TIR and eHbA1c in adult patients with type 1 diabetes. Patients with lower glycemic variability usually have higher %TIR in the same eHbA1c level. Disclosure Y. Zhou: None. J. Weng: None. H. Liu: None. D. Yang: None. H. Ai: None. J. Lv: None. X. Mai: None. W. Xu: None. B. Yao: None. J. Yan: None. Funding National Key Research and Development Program of China (2017YFC1309600)