Continuous glucose monitoring system: dawn period calibration does not change accuracy of the method.

INTRODUCTION Continuous glucose monitoring system is a valuable instrument to measure glycemic control, which uses a retrospective calibration based upon 3 to 4 capillary glucose meter values inserted by the patient each day. OBJECTIVE We evaluated the interference of calibration during the dawn period in the system accuracy. METHODS The monitoring data were retrospectively divided into two groups: with (Group A) or without (Group B) the dawn period calibration (between 1:00 and 5:00 AM). Accuracy of the method was expressed by relative absolute difference. RESULTS Thirty-four continuous glucose monitoring data were evaluated comprising a total of 112 nights. A total of 289 paired readings were analyzed - 195 in Group A and 94 in Group B. We did not find a difference in relative absolute difference (RAD%) in any analyzed period of day by adding dawn calibration. CONCLUSIONS These data suggest that dawn calibration does not alter accuracy of method.