Research

CGM Sensors are good and getting even better

MediSense, a UK/US company acquired by Abbott in 1996, was the first to offer a biosensor for BG monitoring.  Thirty years later, the Abbott FreeStyle Libre system is the current product of that team’s ongoing efforts.

We spoke with John Willis, Ph.D., CEO of Ultradian Diagnostics LLC (bio) who worked at MediSense to get his thoughts on the evolution of CGMs based his 30-year career in BG monitoring and medical devices.

Here are quotes from Dr. Willis.

Currently, there are two major sensor approaches, and both achieve excellent results within their useful life.  


CGM Sensor Options Today

  • Glucose/Oxidase sensors are used by Medtronic, Dexcom and Abbott FreeStyle and typically have a 7- to 10-day useful life.

Science: The enzyme glucose oxidase reacts with glucose, water, and oxygen to form gluconic acid and hydrogen peroxide, which is measured by the sensor.

Abbott FreeStyle uses a mediator rather than oxygen to measure glucose and thus is a calibration-free sensor.  The mediator is quite helpful because oxygen is already low in interstitial fluid.

  • A fluorescent polymer approach is used by Senseonics in their Eversense embedded sensor product.  In the US these sensors have a 90-day life while in Europe they are labeled for up to 180-days with a 365-day model in trials.

Science: Senseonics is the first to commercialize a fluorescent glucose indicating polymer.  This technology has been around for a while and the published results for the Eversense Sensor are surprisingly good.

CGM Sensors will Improve

There are pressures to further enhance CGM technology:

  • Pressure to increase mean accuracy from current ISO requirements of 99% of results within the A (±20%) & B (±30%) Zones of the Consensus Error Grid.
  • A further ISO requirement is that 95% of results greater than 5.5 mmol/l, or 100 mg/dL must be within ±15% of reference. In the future, it could go to 99% within ±15% of reference.
  • Sensors may output glucose amplitude and frequency data to enhance the granularity of measurements and improve accuracy.”

About 80% of revenue for CGM and Pump suppliers comes from Europe and North America.  Despite huge populations of prospective users, the rest of the world is not a major market because of the high costs of the devices and consumables.

Today, most minimally invasive sensors have a useful life of up to 14 days and cost $60 to $70 each.  Online sources may save 20%, but the annual cost of sensors is at least $2000. There is pressure to increase the useful life of sensors because people often use sensors beyond their design life and then obtain unreliable readings.  This pressure to increase useful (design) life while also improving accuracy to meet ISO demands is likely to keep sensor prices high for years.

Black Swan Disruption

There is a black swan on the horizon for CGMs in the form of Apple and Google who each could develop and offer a single chip sensor solution where the cost was radically lower, perhaps under a $1 each. Apple wants the world to depend on its mobile devices and already has strong health capabilities embedded in its phones and watches.  Google has Android which is the dominant mobile OS in the 3rd world and Google seems committed to doing good deeds as long as its ad revenue thrives. Both companies might wait until they could offer a non-invasive BG sensor.

Perhaps anticipating a disruptive entry we may see future systems that integrate both the sensor and pump into the single disposable wireless package.  This multifunction package would justify continued high prices for each disposable.

Martin is the Founder of SelfRx Media and editor-in-chief of Insulin Nation. He's a passionate about sharing knowledge with those affected by Diabetes.

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