Average glucose from hemoglobin A_1c for altered red blood cell lifetimes: Predictions based on a model for hemoglobin...

A model for hemoglobin A_1c (HbA_1c) formation was used to predict the relationship between average glucose (AG) and %HbA_1c under conditions of altered red blood cell lifetime (RCL).

Using a kinetic mass balance model for formation of HbA_1c in red blood cells as a function of age (time in circulation), whole blood %HbA_1c vs. glucose was calculated based on the nonlinear distribution of red blood cells as a function of age across RCL.

Model calculations provided a close fit to the standard relationship of estimated average glucose to %HbA_1c for normal RCL (r>0.999). Results for altered RCL were calculated assuming simple time-scale compression or expansion of the distribution of red blood cells as a function of RCL. For a given %HbA_1c, the operative average glucose needed to have achieved a given %HbA_1c was predicted to be altered by RCL according to average glucose×RCL=constant.

Model calculations estimate the extent to which standard reporting of AG vs. HbA_1c underestimates or overestimates AG under conditions of altered RCL. Conditions of altered RCL may often be operative in patients with certain hemoglobin variants.