How do CGMs work? Abbott, Dexcom or new entrants?

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What’s up with Continuous Blood Glucose Monitors?

The interest in continuous glucose monitoring (CGM) continues to expand to people without diagnosed metabolic impairment and diabetes. Glucose is one of the major fuel sources for all vital functions of the body and large increases or instabilities in glucose can be damaging to your health. Our body’s ability to metabolize and regulate glucose through insulin production affects our sleep, our appetite, our weight, and our energy levels. If we monitor our glucose levels in real-time, we can trend how our bodies 2respond to different foods, exercise, sleep, and environmental factors and ultimately optimize our lifestyle decisions to improve our health.

CGM Method of Measuring Glucose

CGMs measure the amount of glucose that continuously flows from blood vessels and capillaries into the interstitial fluid in the lower level of our skin. When comparing the values from a traditional finger stick and a CGM reading, a CGM is telling you what your capillary blood glucose level was about 10-15 mins ago. This time reflects the amount of time it takes for the glucose to move from the blood to the interstitial fluid.

Actionable Data

In healthy individuals, we assume biomarkers are within normal range but we have no insights into the stability of these biomarkers and how our environment and lifestyle factors affect them. Continuous glucose monitoring has already impacted the treatment of patients on intensive insulin therapy. It now can be used to target individuals with prediabetes or metabolic syndrome symptoms to make beneficial lifestyle changes.

Metabolic Health and Blood Glucose

Metabolic syndrome (MetS) refers to a cluster of metabolic abnormalities including hyperglycemia (elevated blood sugar levels), dyslipidemia (imbalance of blood lipid levels), abdominal obesity and high blood pressure, which is closely associated with the development of type 2 diabetes mellitus and cardiovascular diseases.

The risks of having heart disease, stroke, and diabetes have been shown to be increased by 1.5- to 3-fold in people with MetS when compared to people without MetS. HbA1c and insulin levels are strongly associated with metabolic syndrome criteria, their clustering, and insulin resistance. Insulin resistance can provide early information in subjects prone to developing metabolic syndrome.

How accurate are CGMs?

MARD (mean absolute relative difference) is considered the simplest measurement of sensor accuracy and represents the difference between a CGM system's glucose readings and a reference blood glucose measurement. The lower the MARD, the more accurate the CGM system. Typically a CGM system with a MARD <10% is regarded to have good analytical performance.

Three most common CGMs for metabolic health

Libre 2

Abbott’s Libre 2 is considered a flash glucose reading system, providing readings every 1 minute, and only through scanning of the device. The Libre 2 currently stores 8 hours of data that is transmitted through your smartphone via periodic user scanning of the sensor. This sensor is an iCGM-certified device, meaning it can integrate with other compatible glucose devices like insulin pumps, but unfortunately does not currently support any of these integrations. The Libre 2 has a very simple application method, has a 1-hour sensor warm-up period, and is about the size of a quarter.

Dexcom G6

The Dexcom G6 system is considered a true CGM system, providing readings every five minutes, directly to your smart device, scanning is not necessary. The Dexcom system is also an iCGM-certified device and already integrates with insulin pumps and smart insulin pens. This sensor has a 2-hour warm-up time and compared to the Libre sensors, it has a more complex set-up system and much larger sensors that some users find impractical.

Libre 3

The Libre 3, Abbott’s newest sensor, is also considered a true CGM system, providing readings every 1 minute, directly to your smart device. Similar to the Libre 2, this sensor is an iCGM certified device, but also does not currently support any of these integrations. The Libre 3 also offers a simple application method, a 1 hour warm-up time, and is the size of a penny, making it the most discreet sensor on the market.

Sensible

Sensible is a new entrant from https://sensible.health , that is still in the development stage. It consists of a microneedle patch that is replaceable and a rechargeable transmitter that sits on top of the microneedle patch. This should mean Sensible sensor is a lot cheaper than what exists on the market and should reduce the amount of plastic waste generated by these sensors. Additionally, the sensor doesn't require any scanning and will have APIs to easily get data from the sensors.

So which one is best?

User experience, cost, and length of use should be looked at when deciding which sensor is best for you. Based solely on MARD scores, Libre 3 takes first place with a score of 7.95%, followed by the Dexcom G6, and then Libre 2. Libre sensors generally speaking are easier to put on, smaller and cheaper, however, the Dexcom system provides better alarm settings (making these better for diabetics), has better data sharing between user’s devices, and already integrates with smart insulin systems.