Evaluation of continuous glucose monitoring‐derived person‐specific HbA1c in the presence and absence of complications in type 1 diabetes

AIM: To evaluate the accuracy of a novel kinetic model at predicting HbA1c in a real‐world setting and to understand and explore the role of diabetes complications in altering the glucose–HbA1c relationship and the mechanisms involved. MATERIALS AND METHODS: Deidentified HbA1c and continuous glucose monitoring values were collected from 93 individuals with type 1 diabetes. Person‐specific kinetic variables were used, including red blood cell (RBC) glucose uptake and lifespan, to characterize the relationship between glucose levels and HbA1c. The resulting calculated HbA1c (cHbA1c) was compared with glucose management indicator (GMI) for prospective agreement with laboratory HbA1c. RESULTS: The cohort (42 men and 51 women) had a median age (IQR) of 61 (43, 72) years and a diabetes duration of 21 (10, 33) years. A total of 24 459 days of continuous glucose monitoring (CGM) data were available and 357 laboratory HbA1c were used to assess the average glucose–HbA1c relationship. cHbA1c had a superior correlation with laboratory HbA1c compared with GMI with a mean absolute deviation of 1.7 and 6.7 mmol/mol, r(2) = 0.85 and 0.44, respectively. The fraction within 10% of absolute relative deviation from laboratory HbA1c was 93% for cHbA1c and 63% for GMI. Macrovascular disease had no effect on the model's accuracy, whereas microvascular complications resulted in a trend towards higher HbA1c, secondary to increased RBC glucose uptake. CONCLUSIONS: cHbA1c, which takes into account RBC glucose uptake and lifespan, accurately reflects laboratory HbA1c in a real‐world setting and can aid in the management of individuals with diabetes.