According to an FDA briefing document, the level of accuracy of the G5 mobile continuous glucose monitoring (CGM) system (Dexcom) is “close to, but not as good as, typical self-monitoring blood glucose meters in the U.S. market.” The briefing document was released July 19, two days before a scheduled meeting of the agency’s Clinical Chemistry and Clinical Toxicology Devices Panel.
The FDA staff scientists added, however, that “the Dexcom G5 continuous glucose monitoring system provides contextual information that self-monitoring blood glucose meters do not provide that may lead to users making more informed insulin dosing decisions, and which in turn may allow for better glucose management and outcomes.”
The document noted that many patients who use CGM systems are also likely to use glucose values from those devices (off-label use) in making decisions related to their insulin dosing.
“A significant barrier to these users making better, informed decisions using glucose data from their Dexcom G5 continuous glucose monitoring system device is the labeling restriction currently in place that this device is only to be used adjunctively,” the staff wrote.
The G5 CGM system is currently approved to measure glucose in interstitial fluid as an adjunctive device to complement, not replace, information obtained from blood glucose monitoring devices. Dexcom is seeking FDA approval to claim that the G5 system can be indicated “to replace fingerstick blood glucose testing for diabetes treatment decisions.”
The G5 system consists of a glucose sensor (for detecting interstitial-fluid glucose); a transmitter that converts sensor glucose signals to glucose concentrations and transmits the calculated values to display devices; and a receiver device that displays the glucose concentration received from the transmitter (display devices are either the Dexcom receiver or a mobile device featuring a Dexcom app).
The glucose sensor used in the G5 system was originally approved in 2012 for use in the Dexcom G4 CGM system. A modified algorithm that improved the point accuracy of the G4 device was approved in October 2014 for adults and in May 2015 for children older than 2 years of age. This algorithm change resulted in improved accuracy performance, according to the briefing document. The G5 system has a modified transmitter and receiver compared with the G4 system, but senses or calculates glucose concentrations in the same way. The same clinical data were used to support the accuracy of both the G4 and G5 systems.