Average glucose from hemoglobin A1c for altered red blood cell lifetimes: Predictions based on a model for hemoglobin A1c formation

Abstract

BackgroundA model for hemoglobin A1c (HbA1c) formation was used to predict the relationship between average glucose (AG) and %HbA1c under conditions of altered red blood cell lifetime (RCL). MethodsUsing a kinetic mass balance model for formation of HbA1c in red blood cells as a function of age (time in circulation), whole blood %HbA1c vs. glucose was calculated based on the nonlinear distribution of red blood cells as a function of age across RCL. ResultsModel calculations provided a close fit to the standard relationship of estimated average glucose to %HbA1c 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 %HbA1c, the operative average glucose needed to have achieved a given %HbA1c was predicted to be altered by RCL according to average glucose×RCL=constant. ConclusionsModel calculations estimate the extent to which standard reporting of AG vs. HbA1c underestimates or overestimates AG under conditions of altered RCL. Conditions of altered RCL may often be operative in patients with certain hemoglobin variants.