What is CGM: Dexcom vs Libre Accuracy

In recent years, continuous glucose monitoring (CGM) devices have made the management of diabetes easier than people could imagine. While some of the devices transmit your glucose data every 1, 3, or 5 minutes, most of the latest CGM devices provide real-time glucose readings. This has not only reduced the need for frequent finger pricks but resulted in better A1C levels as well. This blog gives an overview of CGM devices, the most prominent players in the US CGM industry, Abbott and Dexcom, and the comparison between the most accurate CGM sensor models by these companies.

What is a CGM Device?

A CGM device consists of a small sensor that has a microneedle attached to it, which measures glucose levels in the interstitial fluid. These sensors are typically attached at the back of the upper arm (in adults) and can be taken off in case of irritation. This sensor communicates wirelessly with a receiver or a compatible smartphone, providing real-time data about glucose levels.

According to PubMed, “The microneedle sensor of this CGMS uses a 1 mm length needle in a 3 mm × 3 mm microneedle array for percutaneous minimally invasive blood glucose measurement. This size of microneedle does not cause bleeding damage to the body when used.”

Market Leading CGM Sensors:

Most popular CGM devices include but are not limited to, Freestyle Libre by Abbott and the Dexcom G6 by Dexcom. Both of the CGMs offer acceptable accuracy, and the latest models are compatible with automatic insulin delivery systems as well.

And to support an active lifestyle, the latest sensor models by both of these companies are waterproof as well (up to specific feet in pools). Based on all the convenience these sensors provide; both boast a big customer base. However, as many people want insights on Dexcom vs libre accuracy. Here is a precise comparison between the most accurate CGM sensors by both companies;

Freestyle Libre & the Most Accurate Sensors by Abbott

The Freestyle Libre system, developed by Abbott, has become a widely used CGM in both the United States and globally. Takes edge on developing the smallest CGM sensors in the world, i.e.; Freestyle Libre 3 sensor and Freestyle Libre 3 Plus sensor. These are not just the smallest, but the most accurate CGM sensors, with the least MARD (mean absolute relative difference) values.

What is MARD?

This is the parameter for measuring the accuracy of continuous glucose monitors (CGMs). The lower the MARD, the better the accuracy. According to the National Institute of Health, “a CGM system with a MARD <10% is regarded to have good analytical performance.”

MARD Values of Libre 3 and Libre 3 Plus

Freestyle Libre 3 sensor (the first smallest CGM sensor in the world) has an overall MARD value of 7.8%. And the Libre 3 Plus sensor (with the same size as Libre 3) has an overall MARD value of 8%.

Freestyle Libre Accuracy Problems

While Freestyle Libre offers impressive accuracy, some users report discrepancies between the sensor readings and actual glucose levels. This can sometimes occur due to:

• Sensor Placement: The sensor’s position on the skin can affect its readings, especially if not inserted correctly or if it becomes displaced during use.
• Environmental Factors: Extreme temperatures or certain skin conditions can lead to inaccurate readings.
• Time Lag: The sensor measures glucose in interstitial fluid, which can have a time lag compared to blood glucose meter reading that measure your glucose directly from blood. This delay can be up to 5-10 minutes, meaning real-time blood glucose spikes might not immediately show on the Freestyle Libre.

Despite these occasional issues, many users find Freestyle Libre’s convenience and general accuracy to be beneficial for daily diabetes management.

Freestyle Libre Accuracy vs Finger Prick

For comparison, finger prick tests are considered the gold standard for measuring blood glucose, offering immediate, accurate results. However, these tests are invasive, require constant repetition, and can be painful or inconvenient.

When comparing the accuracy of the Freestyle Libre to a finger prick test, the Libre system is often close but may not always be perfectly aligned. In some cases, especially in extreme glucose fluctuations, users report differences between the CGM reading and the results of a finger prick test.

Dexcom & the Most Accurate CGM Sensors by Dexcom

Dexcom is considered as one of the pioneers in the CGM industry. Famous for new inventions, Dexcom usually comes up with unique features and convenience. The latest CGM devices by this brand include Dexcom G6 and Dexcom G7.

Dexcom G6 and G7 Accuracy

The Dexcom G6 and the more recent G7 models are known for their high accuracy and ease of use. The G6 was a significant advancement over previous models with pretty good accuracy. However, some of the users were not quite happy due to its 2-hour warm up time and size not as small as many individuals want.

The Dexcom G7 comes with a quite smaller, and a 30-min warm-up time. However, based on the survey reports many users said they wanted to move back to the Dexcom G6 as they had a much better experience with the G6. While many say they liked Dexcom G6 more than the G7, some users showed satisfaction over the Dexcom G7’s smaller size and quicker warmups.

Dexcom G6 and G7 MARD Values

According to PubMed, “the overall MARD of Dexcom G6 was 12.8%, and median ARD was 10.1%.” The newer Dexcom G7 offers even better performance, with a reported MARD of 8.2% and 9.1%, for the sensors placed on arm and abdomen, respectively. This demonstrates significant improvement in sensor accuracy, helping users manage their diabetes with greater confidence.

Dexcom Accuracy Problems

While both the Dexcom G6 and G7 provide reliable readings, some users report occasional discrepancies. Factors that can contribute to these issues include:

• Sensor Placement: Proper insertion and placement on the skin are essential for accurate readings. If the sensor is not positioned correctly or becomes displaced, it can affect accuracy.
• Environmental Factors: Extreme temperatures may interfere with sensor readings, causing inaccuracies.
•  Time Lag: Like other CGMs, the Dexcom sensors measure glucose levels in interstitial fluid, which may have a time lag compared to blood glucose measurements. This delay is typically a few minutes, meaning blood glucose spikes may not immediately show on the Dexcom device.

Dexcom vs Libre Accuracy

While both Dexcom and Freestyle Libre have their own perks for the users, such as Dexcom usually take edge on bringing innovation, till date, the freestyle libre CGM devices have shown better MARD values. Hence, Abbott shows better accuracy than Dexcom.

Still confused on which CGM device is suitable for you? Check our complete range of CGM sensors here. We at CGM Monitors provide utmost flexibility to our customers. Simply fill out this free Benefit Check form or you may also make a purchase using your Debit/Credit card.

References:

Accuracy of Dexcom G6 Continuous Glucose Monitoring

Accuracy of the Third Generation of a 14-Day Continuous Glucose Monitoring

Accuracy and Safety of Dexcom G7

Disclaimer: This blog contains information based on research and is for informational purposes only. Please always consult a doctor before taking any medical action.