Continuous glucose monitoring and haemoglobin A1c

Abstract

Background: Measurement of HbA1c is the standard test for assessment of glycaemic control in diabetic subjects. Using new glucose sensing technology we re-evaluated the significance of HbA1c in terms of the aspects of the blood profile it measures in patients with diabetes. Methods: In a group of 27 patients with type 1 diabetes, interstitial fluid glucose concentrations were monitored for a mean of 2·6 days using the Continuous Glucose Monitoring SystemTM (MiniMed Inc, CA, USA). Results were correlated with an HbA1c measurement taken at the time of sensor insertion. Results: Results were available in 25 subjects, two datasets being lost due to patient error. There was a correlation between mean sensor glucose value, and the HbA1c value ( r=0·59, P=0·002). The correlation with standard deviation of the readings was weaker (r=0·3, P=0·15). No other descriptor of the sensor glucose concentration correlated with HbA1c. Conclusion: The mean interstitial glucose concentration recorded with the Continuous Glucose Monitoring System correlates with HbA1c level recorded at the time, but with no other marker of glucose control in diabetic subjects. These results have implications for the interpretation of HbA1c concentrations in type 1 diabetes.