Implantable continuous glucose monitoring, soon to come.

The study shows that implantable CGM is safe and effective. This would be another useful tool, particularly for type 1 diabetes. A group of 71 participants were followed for 180 days.



Diabetes Care

Original Article

January 2017

Objective: It is known that continuous glucose monitoring (CGM) systems can lower mean glucose compared with episodic self-monitoring of blood glucose. Implantable CGM systems may provide additional benefits.

Research Design and Methods: We studied the Eversense (Senseonics Inc.) implantable CGM sensor in 71 participants aged 18 years and older with type 1 and type 2 diabetes in a 180-day multinationalmulticenter pivotal trial. Participants used the CGM system at home and in the clinic.

CGM accuracy was assessed during eight in-clinic visits with the mean absolute relative difference (MARD) for venous reference glucose values >4.2 mmol/L as the primary end point.

Secondary end points included Clarke Error Grid Analysis and alarm performance. The primary safety outcome was device-related serious adverse events. This trial is registered with, number NCT02154126.


The MARD value against reference glucose values >4.2 mmol/L was 11.1% (95% CI 10.5, 11.7). Clarke Error Grid Analysis showed 99.2% of samples in the clinically acceptable error zones A and B.  81% of hypoglycemic events were detected by the CGM system within 30 min. No device-related serious adverse events occurred during the study.


Our results indicate the safety and accuracy of this new type of implantable CGM system and support it as an alternative for transcutaneous CGM.


People with diabetes frequently use fingerstick capillary glucose measurements to guide their dosing decisions. Continuous glucose monitoring (CGM) systems can provide glucose data in real time and reduce the need for fingerstick testing. Additionally, people with diabetes can receive temporal information, trend information, and alarms for impending hypoglycemic and hyperglycemic events. When used regularly, CGM can effectively lower mean glucose compared with fingerstick glucose measurements only. Unfortunately, wear time of current transcutaneous CGM is low in some populations, which might partially be explained by usability issues.

The need for implantation and removal through a minor surgical procedure imposes some discomfort on the patient. Currently, no long-term data on implanted sensor accuracy or longevity are available. In this multinational, multicenter European trial, we aimed to investigate the safety and accuracy of a new type of CGM system using an implantable glucose sensor. In addition, we assessed sensor lifetime, system wear time, participant-reported outcome measures, and measures of glycemic control.

The current study, investigating the accuracylongevity, and impact on the patient experience of a novel implantable CGM system, showed safety and accurate performance of the investigational device over the full sensor life. Participant acceptance of the device was high. The current system was accurate, with an overall MARD of 11.1% for samples >4.2 mmol/L (75 mg/dL). CGM performance was less in the hypoglycemic range, as is also seen with other CGM products.

Device use coincided with a significant reduction in HbA1c, consistent with the results of a meta-analysis showing that HbA1c lowering with CGM use depends on baseline HbA1c and device wear time. The Clarke Error Grid Analysis estimated high clinical performance, with 99.2% of samples in the clinically acceptable error zones A and B.

Results from questionnaire data indicated high participant acceptance of the system but did not register improved perceived generic quality of life, as assessed per SF-36 questionnaire. Nonetheless study participants did describe the ease of use, ability to remove the transmitter without removing the sensor, and availability of on-body vibration alerts as beneficial features of the system. Participants used the CGM for >23 h per dayover the full study duration, indicating high acceptance of the system. The implantation, use, and removal of 147 glucose sensors in 71 participants resulted in a limited number of mild to moderate skin reactions and skin infections, and no device- or procedure-related serious adverse events were reported.

The multicenter approach with real-life use of the system at home and the long duration of the study allowed for assessment of glycemic outcomes, device acceptance, and impact on quality of life on top of system performance. It should be noted that these are uncontrolled observational data. As in most studies testing novel diabetes technology, it can be expected that a more technology-enthusiastic population was included in the study. Also, participants with type 2 diabetes and participants of non-Caucasian descent were underrepresented in this study; as such, one should be careful to directly translate the outcomes of the current study to the wider population.

The results from this study indicate that the use of a long-term implantable continuous glucose sensor is both effective and safe and provides specific usability benefits. The results support implantable CGM as a worthy alternative to current transcutaneous CGM.