Metrics for monitoring glycemic control.

摘要

To the Editor: Hemoglobin A_(1c) (HbA_(1c)) measures contain information regarding mean blood glucose (MBG) as well as MBG-independent factors. In their Commentary, Drs Ru-binow and Hirsch pointed out that the presence of considerable between-patient variation in HbA_(1c) values not due to MBG poses an important challenge for clinical interpretation of HbA_(1c) tests. The hemoglobin glycation index (HGI) was created specifically to quantify and assess this MBG-independent component of HbA_(1c) measurement. HGI is the difference between a patient's observed HbA_(1c) value and the predicted HbA_(1c) value (calculated by inserting the patient's observed MBG into the population regression equation of HbA_(1c) vs MBG). HGI is highly correlated with HbA_(1c) values but statistically independent of MBG values. In an analysis of data from the Diabetes Control and Complications Trial, we used HGI to demonstrate that HbA_(1c) level was a predictor of retinopathy and nephropathy that was statistically independent of MBG level. The authors referenced a critique by Lachin et al that questioned the value of HGI and its strong association with complications because it is not independent of HbA_(1c) level. As HGI is a component of HbA_(1c) measurement, it cannot beindependent of HbA_(1c) level. But it is independent of MBG values and thus can be used to assess the importance of MBG-independent variation in HbA_(1c) values as a predictor of complications.