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

BACKGROUND

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

METHODS

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

RESULTS

Model calculations provided a close fit to the standard relationship of estimated average glucose to %HbA 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, the operative average glucose needed to have achieved a given %HbA was predicted to be altered by RCL according to average glucose×RCL=constant.

CONCLUSIONS

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