Stability, Accuracy, and Risk Assessment of a Novel Subcutaneous Glucose Sensor

Background: Users of continuous glucose monitoring (CGM) systems are concerned with the frequency of inserting and calibrating new sensors, with sensor accuracy and reliability throughout the sensor's functional life, and with the risks associated with inaccurate sensor readings.

Methods: A sensor for our next-generation CGM system was tested for accuracy by comparison with self-monitored blood glucose (SMBG) values throughout 10 days of wear. Fifty subjects (49 with type 1 diabetes, 1 with type 2 diabetes, 20 male, mean ± standard deviation [SD] age 32.5 ± 18.7 years) enrolled. Subjects wore one sensor each, calibrated it once per day, and obtained multiple daily SMBG values for comparison. A total of 2739 paired CGM-SMBG values were analyzed to arrive at standard accuracy statistics and plotted on the surveillance error grid (SEG) to estimate the risk of SMBG-CGM discrepancies.

Results: The overall mean and median absolute relative difference (ARD) values were 9.6% and 7.2%, respectively. The median ARD values ranged from 8.9% on Day 1 to 6.5% on Day 10. SEG analysis categorized 2727 points (99.6%) as "no" or "slight" risk and 12 points (0.4%) as "moderate" or "great" risk. Thirty-nine (79.6%) of the 49 systems worked through the end of Day 10. Sensors and adhesives were well tolerated, with minimal erythema and induration.

Conclusions: This new CGM system's accuracy throughout its 10-day functional life, the convenience associated with once-daily calibrations, and the high proportion of measurements in the "no risk" zone of the SEG support its nonadjunctive use in diabetes management and closed-loop insulin delivery systems.