Comparison of continuous glucose monitoring systems

The comparison covers types of the equipment I have personal experience with (sorted alphabetically):

There are other types of equipment I did not have a possibility to evaluate yet:

In general, all compared systems operate on the same principles and all of them are composed of a sensor, a transmitter and a receiver.

Medtronic receivers are more robust both physically and in their software. They are better customizable and have a wider set of functions, including predictive alarms, ability to scroll through the previously measured glucose values and they display time passed since the sensor has been started. Medtronic receivers operate on standard AAA batteries that are easy to exchange and can be immersed (though, only in fresh water, not sea water). Dexcom receivers have a built in battery that needs to be recharged approximately every 3 days and are protected against dripping water only. This limits Dexcom systems usage during water sports and multiple day outdoor activities. On the other hand Dexcom calibration is based on values measured by the sensor before the blood glucose value entry while Medtronic calibration is based on values measured after the blood glucose value entry. The Dexcom calibration method and the fact, that Dexcom devices do not stop showing glucose values after the expiration of 12 hours period since the last calibration, allows Dexcom technology users to select right times for precise calibration. The ability to calibrate more precisely combined with fewer less averaging algorithms leads Dexcom technology to be more precise and have lower lag between glucose values measured by blood glucose meter and continuous glucose monitoring system.

The signal between the Dexcom transmitter and receiver is stronger; therefore, it is possible to keep a greater distance between them. I have rarely experienced problems with lost communication when I covered the Dexcom transmitter with my palm or any other part of my body or let the receiver to fall off the bed during the night. This was a frequent problem with Medtronic. On the other hand the Dexcom receivers communicate with the transmitter every 5 minutes while Medtronic does it every 10 seconds. If the communication fails, Dexcom systems lose the actual glucose value(s) while Medtronic’s transmitter keeps them in its memory and can transfer them when the connection is re-established. Also, the Medtronic transmitter can be disconnected from the inserted sensor and re-connected again which is not possible with Dexcom.

Dexcom sensors are inserted manually. This means that the speed of skin penetration is lower and can be controlled. Dexcom sensor electrodes are purely metallic, adhesive material area of the sensor base is large and the transmitter is attached to the sensor from the top. This construction maximally limits irritation of the insertion site, leads to the longer life time of sensors and is gentler to insertion sites. Medtronic sensors are inserted with the spring operated serters. They are metallic on polyimide (plastic) base. The adhesive material area is small and the transmitter is attached to the sensor from the side. This may irritate the insertion site by subtle movements of the transmitter when the body moves. It may also mean that tape is required to keep the sensor in place for the duration of the sensor.

Dexcom, unlike Medtronic, neither displays nor stores the values of the measured electrical parameter. In addition, the set of data that can be downloaded from Dexcom devices is smaller which brings more limitations to Dexcomm’s custom made data analyses. The Dexcom software for data upload from the receiver is installed on the PC locally and all the data is stored on a local disc as well. Medtronic uses a dedicated web site to upload, analyse and store the data. There might be some advantages of this solution but I do not feel comfortable with having my private data placed somewhere on the internet.

The table below shows detailed comparison. Background colours indicate my evaluation of the parameter:

Criteria Dexcom Seven® Plus Dexcom G4TM Medtronic Paradigm® 522 and 722 Medtronic Paradigm® 554 and 754 (VEO)
Device type Standalone CGMS Standalone CGMS Insulin pump with CGMS functionality Insulin pump with CGMS functionality
Accuracy
Average lag between blood glucose values and glucose values displayed by the system in my case 7 minutes 40 seconds To be evaluated 12 minutes 10 seconds 9 minutes 40 seconds
Clarke error grid available in the user guide Yes Yes Yes No
Functionality
Measured glucose value range 2.2 - 22.2 mmol/l 2.2 - 22.2 mmol/l 2.2 - 22.2 mmol/l 2.2 - 22.2 mmol/l
Measured values displayed every 5 minutes 5 minutes 5 minutes 5 minutes
Request for re-calibration every 12 hours 12 hours 6 hours for first one, 12 hours for all next 12 hours
Device stops showing glucose values if not re-calibrated in time No No Yes Yes
Graphs show values for last 1, 3, 6, 12 and 24 hours 1, 3, 6, 12 and 24 hours 3 and 24 hours 3, 6, 12 and 24 hours
Number of values displayed in graph 1-hour graph: 12 (all)
3-hour graph: 36 (all)
6-hour graph: 72 (all)
12-hour graph: 144 (all)
24-hour graph: 288 (all)
1-hour graph: 12 (all)
3-hour graph: 36 (all)
6-hour graph: 72 (all)
12-hour graph: 144 (all)
24-hour graph: 288 (all)
3-hour graph: 36 (all)
24-hour graph: 36 (every 8-th)
3-hour graph: 36 (all)
6-hour graph: 36 (every 2-nd)
12-hour graph: 36 (every 4-th)
24-hour graph: 36 (every 8-th)
Possibility to scroll through historical values No No Yes Yes
Trend arrows Yes Yes Yes Yes
Trend arrows delayed against graph by 10 minutes 10 minutes 10 minutes 10 minutes
High and low glucose alerts Yes Yes Yes Yes
High and low glucose alerts show High or low value limit High or low value limit actual glucose value actual glucose value
Low glucose alert values 3.3, 3.9, 4.4, 5.0, 5.5 mmol/l
or 60, 70, 80, 90, 100 mg/dl
3.3 - 5.5 mmol/l in steps of 0.28 mmol/l
or 60 - 100 mg/dl in steps of 5 mg/dl
2.2 – High glucose alert value minus 0.6 mmol/l in steps of 0.1 mmol/l
or 40 – High glucose alert value minus 10 mg/dl in steps of 1 mg/dl
2.2 – High glucose alert value minus 0.6 mmol/l in steps of 0.1 mmol/l
or 40 – High glucose alert value minus 10 mg/dl in steps of 1 mg/dl
High glucose alert values 6.7 - 22.2 mmol/l in steps of 1.1 mmol/l
or 120 - 400 mg/dl in steps of 20 mg/dl
6.7 - 22.2 mmol/l in steps of 0.55 mmol/l
or 120 - 400 mg/dl in steps of 10 mg/dl
Low glucose alert value plus 0.6 - 22.2 mmol/l in steps of 0.1 mmol/l
or Low glucose alert value plus 10 - 400 mg/dl in steps of 1 mg/dl
Low glucose alert value plus 0.6 - 22.2 mmol/l in steps of 0.1 mmol/l
or Low glucose alert value plus 10 - 400 mg/dl in steps of 1 mg/dl
Number of high and low glucose alert values which can be set during the day 1 1 1 8
Rise / fall alert Yes Yes No Yes
Rise / fall rate values 0.11 and 0.17 mmol/l/min
or 2 and 3 mg/dl/min
0.11 and 0.17 mmol/l/min
or 2 and 3 mg/dl/min
No 0.065 - 0.275 mmol/l/min in steps of 0.005 mmol/l/min
or 1.1 - 5.0 mg/dl/min in steps of 0.1 mg/dl/min
Predictive alerts No No No Yes
Alert fired in advance of reaching low or high glucose No No No 5 - 30 min in steps of 5 min
Sensor instability indication Yes Yes No No
Time of last measurement is displayed No Yes Yes Yes
Actual value of electrical parameter is displayed No No Yes Yes
Information about actual length of sensor relation No
alarms 6, 2, and 0.5 hours before relation end
Yes Yes Yes
Blood glucose range for calibration 2.2 - 22.2 mmol/l
or 40 - 400 mg/dl
1.1 - 33.3 mmol/l
or 20 - 600 mg/dl
2.2 - 22.2 mmol/l
or 40 - 400 mg/dl
2.2 - 22.2 mmol/l
or 40 - 400 mg/dl
Possibility to personalize the device (language, glucose units, time) No Yes Yes Yes
Event log (insulin, food, exercise, …) Advanced Advanced No Basic
Receiver
Receiver size length: 114 mm
width: 58 mm
height: 22 mm
length: 101 mm
width: 46 mm
height: 13 mm
Paradigm 522
length: 76 mm
width: 51 mm
height: 20 mm

Paradigm 722
length: 94 mm
width: 51 mm
height: 20 mm
Paradigm 554
length: 83 mm
width: 51 mm
height: 20 mm

Paradigm 754
length: 94 mm
width: 51 mm
height: 20 mm
Receiver weight (including battery) 100 g 69 g Paradigm 522: 100 g

Paradigm 722: 108 g
Paradigm 554: 95 g

Paradigm 754: 102 g
Display type Black & white Colour Black & white Black & white
Display size length: 49 mm
height: 33 mm
length: 46 mm
height: 35 mm
length: 49 mm
height: 21 mm
length: 49 mm
height: 21 mm
Graph size length: 28 mm
height: 30 mm
length: 39 mm
height: 25 mm
length: 19 mm
height: 12 mm
length: 19 mm
height: 12 mm
Battery type Rechargeable, built in Rechargeable, built in Exchangeable, AAA type Exchangeable, AAA type
Battery to be exchanged / recharged 3 days 3 - 5 days 10 days 10 days
Water resistance (see section Ingress Protection rating codes for details) Not certified IP22 IPX7 IPX7
Transmitter
Size (including sensor base) length: 38 mm
width: 23 mm
height: 10 mm
length: 38 mm
width: 23 mm
height: 13 mm
length: 42 mm
width: 35 mm
height: 9 mm
length: 40 mm
width: 35 mm
height: 9 mm
Battery type Non-rechargeable, built in Non-rechargeable, built in Rechargeable, built in Rechargeable, built in
Battery to be recharged / replaced 1 - 2 years to replace 6 - 12 months to replace 7 days to recharge
2 years to replace
7 days to recharge
2 years to replace
Water resistance (see section Ingress Protection rating codes for details) IPX7 IP28 IPX8 IPX8
Transmitter and receiver connect every 5 minutes 5 minutes 10 seconds 10 seconds
Number of glucose values stored in transmitter in case of lost communication 0 0 0 8 (40 minutes)
Declared maximum distance between transmitter and receiver 1.5 meters
effectively higher
6 meters 1.5 meters
effectively lower
1.5 meters
effectively lower
Sensor
Native sensor Seven G4 Platinum Sof Enlite
Length of sensor relation 7 days 7 days 3 days 6 days
Average sensor life time in my case 14 days 14 days 6 days 6 days
Occasional bleeding during sensor insertion in my case No No Yes No
Occasional irritation of insertion site in my case No No Yes Yes
Initial period between sensor start and first calibration 2 hours 2 hours 2 hours 2 hours
Possibility to start sensor relation without initial period No No Yes if sensor is inserted and connected to transmitter for more than 2 hours Yes if sensor is inserted and connected to transmitter for more than 2 hours
Possibility to re-connect transmitter to sensor No No Yes Yes
Sensor material Platinum / silver Platinum / silver Gold / chrome on polyimide base Gold / chrome on polyimide base
Reagents Glucose oxidase Glucose oxidase Glucose oxidase in Bovine Serum Albumin (BSA) Glucose oxidase in Bovine Serum Albumin (BSA)
Sensor size length: 13 mm
diameter at the base: 0.4 mm
diameter at the end: 0.3 mm
length: 13 mm
diameter at the base: 0.25 mm
diameter at the end: 0.25 mm
length: 14 mm
width: 0.7 mm
height: 0.5 mm
length: 9 mm
width: 0.4 mm
height: 0.15 mm
Degree of sensor insertion 45o 45o 45o 90o
Data download
Software for data download / evaluation stored on Local drive,
distributed on CD
Local drive,
downloadable from Dexcom web site
Internet Internet
Downloaded data stored on Local drive Local drive Internet Internet