Current methods of assessing blood glucose control in diabetes

Abstract

The HbA1c measurement effectively "averages" blood glucose over the previous few months, but can conceal wide variations during that period and patients with apparently well-controlled HbA1c may have very different risks of potentially debilitating hypoglycaemia. Self-monitoring of blood glucose provides only "snapshots" of glycaemic control that are unlikely to reveal the true extent of glucose variability. Continuous glucose monitoring (CGM) systems offer a far more comprehensive 24-hour picture of glycaemia, but need regular calibration, are expensive, and limited by short sensor life. Also, the sheer volume of data from CGM downloads can render it difficult to identify patterns. The ambulatory glucose profile (AGP) presents glucose data in a standardised manner, with glucose values presented as a median with 10th, 25th, 75th and 90th centiles. Examination of the AGP can reveal patterns highlighting areas of hypoglycaemia risk or excessive glucose variability, in a way that helps patients to understand and accept the needed changes to their treatment. Software for analysis is available for current systems to indicate possible areas for attention, for example a simple traffic light system where the colour red shows a possible area of risk. AGP could make the difference between identifying or missing a glycaemic pattern and an associated effective therapeutic change, within the time-pressured and resource-limited healthcare environment. Finally, the newer technique of "flash glucose monitoring" involves a small factory calibrated sensor which can store glucose data for up to 8 hours; users use a handheld receiver to "interrogate" the sensor rather than having information pushed through continuously as in CGM.