Addressing shortfalls of laboratory HbA(1c) using a model that incorporates red cell lifespan

Laboratory HbA(1c) does not always predict diabetes complications and our aim was to establish a glycaemic measure that better reflects intracellular glucose exposure in organs susceptible to complications. Six months of continuous glucose monitoring data and concurrent laboratory HbA(1c) were evaluated from 51 type 1 diabetes (T1D) and 80 type 2 diabetes (T2D) patients. Red blood cell (RBC) lifespan was estimated using a kinetic model of glucose and HbA(1c), allowing the calculation of person-specific adjusted HbA(1c) (aHbA(1c)). Median (IQR) RBC lifespan was 100 (86–102) and 100 (83–101) days in T1D and T2D, respectively. The median (IQR) absolute difference between aHbA(1c) and laboratory HbA(1c) was 3.9 (3.0–14.3) mmol/mol [0.4 (0.3–1.3%)] in T1D and 5.3 (4.1–22.5) mmol/mol [0.5 (0.4–2.0%)] in T2D. aHbA(1c) and laboratory HbA(1c) showed clinically relevant differences. This suggests that the widely used measurement of HbA(1c) can underestimate or overestimate diabetes complication risks, which may have future clinical implications.