Hi-R-Ed Online

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Proven Benefit

However, simply having data does not necessarily reduce hypoglycemic events. The presence of real time alerts to warn of impending hypoglycemia makes a profound difference in the occurrence of hypoglycemia. This is an important consideration in the choice of CGM devices.

Alerts increase confidence in insulin dosing as we have a warning before hypoglycemia occurs.

How it works

CGM devices are all comprised of three pieces, the sensor with an inserted sub Q filament,

A transmitter that sends the sensor signal to the patient (Some devices include the sensor and transmitter in a single piece, others have them as separate items)

And a receiver that displays data. This may take the form of an insulin pump, a handheld receiver device, or an app on a smart phone.

Glucose sensor is inserted in subcutaneous tissue and connected to a transmitter

Glucose sensor sends minute electrical signals to the transmitter

Transmitter sends data wirelessly to a pump or handheld monitor, where data can be viewed and acted upon in real-time

System performance

1. Sensor wear is generally 6-14 days, though implanted CGM device sensors are currently approved for 90 days of continuous use.

2. All sensors have a warm-up period where after insertion when they do not transmit data, typically 2-3 hours.

3. Systems vary in accuracy and in what range they are most accurate. Accuracy is an important consideration when values will be used to calculate insulin dosage.

Accuracy

Clarke error grid: 98%+ in zones A & B
(low risk of accidental insulin overdose)

Mean absolute difference (real-time CGM vs YSi)
Dexcom G5: 9-10% Medtronic Enlite: 12-14%

Freestyle Libre 11-12%

CGM system accuracy

Mean Average Relative Difference (MARD) is a measure commonly used to determine the accuracy of continuous glucose monitors. The relative values for sensors vary, and sensors with higher MARD values tend to show a wider range of inaccuracy at values above target range and below about 100 mg/dl.

MARD Compared to YSI (lab)
Freestyle Libre: 11.4%
Medtronic Guardian: 10.6%
Dexcom G6: 9.9%
Senseonics™ Eversense®: 8.8%

1 Wadwa et al. Diab Tech & Ther, 20:6, 2018 (0 cal/day)

2 FDA SSED P160017/S017, 2/13/2018 (2 cal/day)

3 Bailey et al. Diab Tech & Ther, 17:11, 2015 (0 cal/day)

4 PRECISE II: Diab Tech & Ther, 20:3, 2018 (2 cal/day)

5 Precision Data—Date on File—Senseonics 2017