FDA advisory panel to discuss CGM as replacement for SMBG

An FDA advisory panel will vote today on whether to recommend a change in intended use for Dexcom’s G5 Mobile Continuous Glucose Monitoring System, allowing patients with diabetes to use the device to make diabetes treatment decisions without confirmation from a blood glucose meter.

Currently, the Dexcom G5 CGM system is indicated for detecting trends and tracking patterns in blood glucose in patients with diabetes as an adjunctive device to complement — but not replace — information obtained from standard home glucose monitoring devices. Dexcom is seeking to modify the current indication to state that the G5 CGM system is designed to replace finger stick blood glucose testing for diabetes treatment decisions (a non-adjunctive indication), including determining an insulin dose, ingesting carbohydrates, or assessing when to wait before dosing or eating.

The change to the indication will not require changes to the system components, and the system will still require calibration with a finger stick taken by self-monitoring of blood glucose (SMBG) every 12 hours, according to meeting briefing papers prepared by Dexcom. The primary modification will be in the Instructions for Use.

In briefing papers, Dexcom noted that CGM has been shown to provide a significant benefit in diabetes treatment, including reduced excursions of hypoglycemia and hyperglycemia and reduced HbA1c, and there is a need to expand its use.

“However, this expansion is currently limited by the indicated requirement to confirm CGM

readings with SMBG before making treatment decisions,” the researchers wrote. “Some users who are already using CGM trust it enough to make treatment decisions, thereby using the device off-label. Dexcom is unable to train these patients in the proper use of CGM to make treatment decisions, because doing so would be promotion of unapproved uses. In order to expand CGM to a broader population and to provide appropriate training, Dexcom is seeking to revise the indications for use.”

In an executive summary, reviewers with the FDA’s Clinical Chemistry and Clinical Toxicology Devices Panel of the Medical Devices Advisory Committee noted that CGMs are less accurate than blood glucose measurements (particularly in children), and there may be a lag between the blood glucose value and the interstitial glucose value at times when blood glucose concentrations are rapidly changing.

“Inaccurate glucose results may lead to inappropriate treatment decisions that ... may lead to adverse events or diabetes complications,” the reviewers wrote. “However, CGMs provide additional information in the form of continuous trends that may reduce the negative impact of a more inaccurate point estimate of glucose concentration.”

Following discussions with the FDA, Dexcom conducted two simulations: the first evaluated the safety and effectiveness of CGM relative to SMBG in patients with type 1 diabetes over a 2-week period; the second evaluated the risks of hypo-and hyperglycemia in type 1 diabetes with meal-time insulin decisions based on CGM vs. SMBG. A Human Factors Usability Study evaluated the revised Instructions for Use.

The reviewers noted that human-factors related risks of non-adjunctive CGM use may vary based on user group and their level of training, and requested the panel’s input regarding Dexcom’s role in providing appropriate labeling or training on using trend information.

“There do not appear to be generally accepted clinical guidelines or recommendations in the clinical community for how glucose trend information should be taken into account when making treatment decisions with CGM,” the reviewers wrote. “This issue was not specifically addressed by Dexcom in their human factors studies and therefore it is unclear whether users will know how to appropriately use non-adjunctive CGM information in determining treatment.”

Kelly Close, president and founder of Close Concerns and founder of the diaTribe foundation, who will speak during the open public hearing, said the potential change could improve quality of life for patients with diabetes.

“Diabetes is really hard, and I think if they do vote to recommend this new indication it really does acknowledge what is happening in the real world,” Close told Endocrine Today. “Many Dexcom users, including me, regularly use CGM alone to adjust their insulin doses. I think it would mean a lot to me and to other patients if the FDA acknowledged what is happening in the real world. It’s not possible to always stop and do a finger stick [ to measure blood glucose]. I think the label update would help patients maximize benefit and minimize risk.”

The panel’s recommendations are nonbinding, although the FDA often follows its suggestions. – by Regina Schaffer

Disclosure: Close is the president and founder of Close Concerns and founder of the diaTribe foundation.