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An improved biokinetic model describing the haemoglobin A1c ketoamine fraction (HbA1c), and the haemoglobin A1d aldimine fraction (HbA1d), as a function of preceding blood glucose levels has been studied. The model requires knowledge of the chemical reaction rate constants and the life span of the erythrocytes. Calculated HbA1c corresponding to constant blood glucose levels was about 6% lower than previously found using a simplified method of calculation. The predicted variations in the glycated haemoglobins in response to simulated variations in the glucose concentration were, however, similar to the improved and the simplified model calculations. Thus, HbA1d reached a new steady state level within 24 h and HbA1c within 4 weeks after sudden change in glucose concentration. When the blood glucose concentration was simulated by sine waves with periods from 2 to 60 days it was observed that the HbA1d varied in parallel with the glucose concentration with a time delay of about 2 h, whereas the HbA1c was almost constant with periods less than 7 days. Haemoglobin A1c predicted from observed blood glucose levels in diabetic patients followed over several weeks varied in parallel with measured HbA1c. However, the measured values were systematically higher than the calculated. This could be due to an underestimation of the daily mean blood glucose levels used for calculation of HbA1c or to inaccurate estimates of the reaction rate constants. Based on the model it could be demonstrated that the HbA1c fraction corresponds to an exponentially weighted average of daily mean blood glucose levels over the preceding 4 weeks.(ABSTRACT TRUNCATED AT 250 WORDS)
Mortensen et al. (Fri,) studied this question.