Fig. 1(A) Representative blood glucose (BG) monitoring data obtainable with self-monitoring of blood glucose (SMBG; in green) and with continuous glucose monitoring (CGM; in blue). Dotted circles denote hyperglycemic and hypoglycemic episodes that, using only SMBG measurements, are not detectable. (B) Assessment of the accuracy of a CGM sensor can be performed by comparing Yellow Spring Instruments Inc. (YSI) measurements (red stars) versus Dexcom G4 Platinum CGM (black solid line) measurements. For example, mean absolute relative difference can be calculated as the average ratio between the absolute difference between the CGM measurements and the YSI over the YSI.
Fig. 2Accuracy evolution of state-of-the-art CGM systems through years. From the left: Medtronic Enlite, Abbott Freestyle Navigator, Dexcom G4 Platinum, Abbott Freestyle Libre, Dexcom G4 Platinum with 505 software, Senseonics Eversense, Dexcom G5, Dexcom G6. MARD, mean absolute relative difference; SMBG, self-monitoring of blood glucose.
Table 1Summary of the main characteristics in terms of accuracy, features, and limitations of state-of-the-art CGM sensor devices
Manufacturer |
CGM system |
Accuracy (MARD), % |
Calibrations |
Sensor lifetime, day |
Smart features |
Main limitations |
Medtronic |
Enlite Sensor |
13.6 |
Every 12 hr |
6 |
Trend arrows, rate-of-change alerts, hypo/hyperglycemic alarms, integration with Medtronic's pumps |
Approved only for as an adjunctive device, acetaminophen interference |
Guardian Sensor 3 |
10.6 (abdomen) 9.1 (arm) |
Every 12 hr |
7 |
Trend arrows, rate-of-change alerts, hypo/hyperglycemic alarms, integration with Medtronic's pumps |
Approved only for as an adjunctive device, acetaminophen interference |
Abbott |
Freestyle Navigator II |
14.5 |
2, 10, 24, 72 hr after insertion |
5 |
Trend arrows, rate-of-change alerts, hypo/hyperglycemic alarms |
Approved only in some European countries as adjunctive device |
Freestyle Libre |
11.4 |
No |
14 |
Trend arrows |
Sensor need to be scanned to get a glucose reading, not recommended for patient with hypoglycemic unawareness, confirmatory SMBG still recommended when specific episodes occur |
Freestyle Libre 2 |
Not available |
No |
14 |
Trend arrows, rate-of-change alerts, hypo/hyperglycemic alarms, remote monitoring |
Sensor need to be scanned to get a glucose reading, not recommended for patient with hypoglycemic unawareness, confirmatory SMBG still recommended when specific episodes occur |
Dexcom |
G4 Platinum |
9 |
Every 12 hr |
7 |
Trend arrows, rate-of-change alerts, hypo/hyperglycemic alarms, remote monitoring |
Approved only as an adjunctive device |
G5 Mobile |
9 |
Every 12 hr |
7 |
Trend arrows, rate-of-change alerts, hypo/hyperglycemic alarms, remote monitoring, wireless communication with up to 5 devices |
Confirmatory SMBG still recommended when specific episodes occur, acetaminophen interference |
G6 |
10 |
No |
10 |
Trend arrows, rate-of-change alerts, hypo/hyperglycemic alarms, remote monitoring, wireless communication with up to 5 devices |
Confirmatory SMBG still recommended when specific episodes occur |
Senseonics |
Eversense |
11.4 |
No |
90 |
Trend arrows, rate-of-change alerts, hypo/hyperglycemic alarms |
The sensor needs to be inserted and removed in doctor's office, approved as adjunctive device in Europe only |