Customers Report Points With New Glucose Monitor Mannequin

The know-how has come a great distance in recent times. Within the 2010s, these gadgets required blood glucose calibrations twice a day and nonetheless weren’t dependable sufficient to dose insulin based mostly on the readings. Now, some insulin pumps use the near-real-time information to mechanically make changes. With these enhancements has come higher belief within the information customers obtain—and better requirements. A defective studying might end in a harmful dose of insulin.

The G7 launched a number of adjustments to Dexcom’s earlier designs, together with a a lot smaller footprint, and up to date the algorithm used to translate sensor alerts into glucose readings for higher accuracy, Simpson says. “From a efficiency perspective, we did exhibit in a scientific trial that the G7 is considerably extra correct than the G6,” he says.

So Heller and others have been stunned when the brand new Dexcom sensor appeared to be performing worse. For some batches of sensors, it’s potential that the problem was partially on account of an unvalidated change in a element utilized in a resistive layer of the sensors. The brand new element confirmed worse efficiency, in line with a warning letter issued by the U.S. Meals and Drug Administration in March 2025, following an audit of two U.S. manufacturing websites. The fabric has since been faraway from all G7 sensors, Simpson says, and the corporate is continuous to work with the FDA to deal with issues. (“The warning letter doesn’t limit Dexcom’s capability to provide, market, manufacture or distribute merchandise, require recall of any merchandise, nor limit our capability to hunt clearance of latest merchandise,” Dexcom added in an announcement.)

“There’s a distribution of accuracies that must do with folks’s physiology and in addition the gadgets themselves. Even in our scientific research, we noticed some that have been actually exact and a few that had just a little little bit of inaccuracy to them,” says Simpson. “However typically, our sensor could be very correct.”

In late November Abbott—one in every of Dexcom’s fundamental rivals—recalled a few of its CGMs on account of inaccurate low glucose readings. The recall impacts roughly 3 million sensors and was brought on by a problem with one in every of Abbott’s manufacturing strains.

The discrepancy between reported accuracy and consumer expertise, nonetheless, goes past anyone firm’s manufacturing missteps.

Does MARD Matter?

The accuracy of CGM programs is steadily measured by way of “imply absolute relative distinction,” or MARD, a proportion that compares the sensor readings to laboratory blood glucose measurements. The decrease the MARD, the extra correct the sensor.

This quantity is usually utilized in promoting and advertising, and it has a historic relevance, says Manuel Eichenlaub, a biomedical engineer on the Institute for Diabetes Expertise Ulm in Germany, the place he and his colleagues conduct impartial CGM efficiency research. For years, there was a common perception {that a} MARD below 10 % meant a system could be correct sufficient for use for insulin dosing. In 2018, the FDA established a selected set of accuracy necessities past MARD for insulin-guiding glucose displays, together with Dexcom’s. However producers design the scientific trials that decide accuracy metrics, and the best way research are designed could make an enormous distinction.

When Dan Heller wore the Dexcom G6 and G7 on the identical time, he says he seen the G7 readings have been extra erratic, making it harder to correctly management his blood sugar. Dan Heller

As an example, blood glucose ranges function the “floor fact to match the CGM values towards,” says Eichenlaub. However glucose ranges fluctuate throughout blood compartments within the physique; blood collected from capillaries with a finger prick fluctuates extra and might have glucose ranges round 5 to 10 % larger than venous blood. (Dexcom exams towards a gold-standard venous blood analyzer. When customers see inaccuracies towards dwelling meters that use capillary blood, it might partially be a mirrored image of the meter’s personal inaccuracy, Simpson says, although he acknowledges actual inaccuracies in CGMs as effectively.)

Moreover, the distribution of sampling isn’t standardized. CGMs are identified to be much less correct at the start and finish of use, or when glucose ranges are out of vary or altering shortly. Which means measured accuracy could possibly be skewed by taking fewer samples proper after a meal or late within the CGM’s lifetime.

In keeping with Simpson, Dexcom’s trial protocol meets the FDA’s expectation and exams the gadgets in numerous blood sugar ranges throughout the lifetime of the sensor. “Inside these scientific trials, we do stress the sensors to try to simulate these actual world situations,” he says.

Dexcom and different corporations promote a MARD round 8 %. However some impartial research are extra demanding and discover larger numbers; a head-to-head research of three fashionable CGMs that Eichenlaub led discovered MARD values nearer to 10 % or larger.

Eichenlaub and different CGM consultants imagine that extra standardization of testing and an extension of the FDA necessities are crucial, in order that they lately proposed complete pointers on CGM efficiency testing. In america and Europe, just a few producers presently dominate the market. However newer gamers are getting into the rising market and, particularly in Europe, might not meet the identical requirements as legacy producers, he says. “Having a standardized approach of evaluating the efficiency of these programs is essential.”

For customers like Heller although, higher accuracy solely issues if it yields higher diabetes administration. “I don’t care about MARD. I need information that’s reliably actionable,” Heller says. He encourages engineers engaged on these gadgets to assume just like the affected person. “In some unspecified time in the future, there’s quantitative information, however you want qualitative information.”