Is the response of continuous glucose monitors to physiological changes in blood glucose levels affected by sensor life?

Background: None of the studies concerned with the performance of a continuous glucose monitor (CGM) over time has examined the extent to which extended periods of wear affect the responses of both CGM accuracy and lag time to rapid changes in blood glucose levels. Here we propose a novel approach to address these issues.

Methods: Eight participants without diabetes were each fitted with two CGMs (Paradigm(®) 722 Real-Time [Medtronic, Northridge, CA]; abdominal and triceps regions) and completed fasted oral glucose challenges (OGCs) on six occasions over a 9-day period, while the CGMs were worn without removal. Arterialized blood samples were collected for comparison with CGM values.

Results: There were marked mismatches and lag times between blood glucose and CGM values in response to all OGCs, most notably during the initial rapid increase in glucose levels. Abdominal and triceps CGMs consistently underestimated peak blood glucose by an average of 2.7±0.2 and 2.9±0.2 mM, respectively, and were associated with a peak blood glucose lag of 21.6±1.8 and 18.1±1.6 min, respectively. CGM accuracy did not deteriorate over 9 days of wear in OGCs for either the abdominal or triceps sensor. All participants found the triceps sensor site more comfortable than the abdominal site (P<0.05).

Conclusions: The current CGM sensor tested here may be used for extended periods, providing added economic benefits for the wearer. However, the marked inaccuracy and lag time of CGM readings when blood glucose levels change rapidly within the physiological range must be considered for optimal CGM use in glycemic management.