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. 2025 Feb 4:19322968251315459.
doi: 10.1177/19322968251315459. Online ahead of print.

Performance of Three Continuous Glucose Monitoring Systems in Adults With Type 1 Diabetes

Manuel Eichenlaub  1 , Delia Waldenmaier  1 , Stephanie Wehrstedt  1 , Stefan Pleus  1 , Manuela Link  1 , Nina Jendrike  1 , Sükrü Öter  1 , Cornelia Haug  1 , Maren Schinz  2 , Vincent Braunack-Mayer  2 , Regula Schneider  2 , Derek Brandt  2 , Guido Freckmann  1
Affiliations

Performance of Three Continuous Glucose Monitoring Systems in Adults With Type 1 Diabetes

Manuel Eichenlaub et al. J Diabetes Sci Technol. .

Abstract

Background: The performance of continuous glucose monitoring (CGM) systems is difficult to compare due to different study designs and a lack of head-to-head studies. This study evaluated the performance of FreeStyle Libre 3 (FL3), Dexcom G7 (DG7), and Medtronic Simplera (MSP) against different comparator methods and during clinically relevant glycemic scenarios.

Method: Twenty-four adult participants with type 1 diabetes mellitus wore one sensor of each CGM system in parallel for up to 15 days. Sensors of DG7 and MSP were exchanged on days 5 and 8, respectively. Three 7-hour sessions with 15-minute comparator blood glucose-level measurements using YSI 2300 (YSI, venous), Cobas Integra (INT, venous), and Contour Next (CNX, capillary) were conducted on days 2, 5, and 15. Simultaneously, glucose-level excursions with transient hyperglycemia and hypoglycemia were induced according to a recently published testing procedure. The accuracy was evaluated using various metrics, including mean absolute relative differences (MARDs).

Results: Compared with YSI data, the MARDs of FL3, DG7, and MSP were 11.6%, 12.0%, and 11.6%, respectively. Relative to the INT data, the corresponding MARDs were 9.5%, 9.9%, and 13.9%, respectively, and compared with CNX data, MARDs were 9.7%, 10.1%, and 16.6%, respectively. Both FL3 and DG7 showed better accuracy in the normoglycemic and hyperglycemic range, while MSP performed better in the hypoglycemic range.

Conclusions: Performance results of all CGM systems varied depending on the comparator method. However, across comparators FL3 and DG7 tended to be more accurate compared with MSP. All CGM systems showed a lower accuracy compared with previous studies, emphasizing the need for comprehensive study design guidelines.

Keywords: CG-DIVA; CGM performance; accuracy; comparator method; dynamic glucose regions.

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Conflict of interest statement

Declaration of Conflicting InterestsThe author(s) declared the following potential conflicts of interest with respect to the research, authorship, and/or publication of this article: G.F. is the general manager and medical director of the Institute for Diabetes Technology (Institut für Diabetes-Technologie Forschungs- und Entwicklungsgesellschaft mbH an der Universität Ulm, Ulm, Germany), which carries out clinical studies, for example, with medical devices for diabetes therapy on its own initiative and on behalf of various companies. G.F./IfDT have received research support, speakers’ honoraria, or consulting fees in the last three years from Abbott, Ascensia, Berlin Chemie, Boydsense, Dexcom, Lilly Deutschland, Novo Nordisk, Perfood, Pharmasens, Roche, Sinocare, Terumo, and Ypsomed. M.E., D.W., S.W., S.P., M.L., N.J., S.Ö., and C.H. are employees of IfDT. M.S., V.B.M., R.S., and D.B. have no conflict of interest.

Figures

Figure 1.
Figure 1.
Panel a: Deviation intervals with respect to YSI of the continuous glucose deviation and variability analysis (CG-DIVA) in different glucose ranges covering the US food and drug administration iCGM criteria: the dark gray boxes contain 85%, 70%, 80%, and 87% of expected deviations, respectively, and the light gray boxes contain 98%, 99%, and 99% of expected deviations. Colored dashes show median deviation. Panel b: Sensor-specific median (dot) and 90% range of relative differences to YSI. For DG7 and MSP solid and dashed lines indicate sensors tested before and after sensor replacement, respectively. Abbreviations: FL3, FreeStyle Libre 3 CGM system; DG7, Dexcom G7 CGM system; MSP, Medtronic Simplera CGM system; YSI, YSI 2300 STAT PLUS laboratory analyzer.
Figure 2.
Figure 2.
Diabetes technology society error grid analysis of FL3 (panel a), DG7 (panel b) and MSP (panel c) against YSI data. Abbreviations: FL3, FreeStyle Libre 3 CGM system; DG7, Dexcom G7 CGM system; MSP, Medtronic Simplera CGM system; YSI, YSI 2300 STAT PLUS laboratory analyzer; CGM, continuous glucose monitoring.
Figure 3.
Figure 3.
Mean time course of comparator and CGM glucose data during the first half of the frequent sampling period (FSP, panel a) and surrounding hypoglycemia (panel b). In panel b, all measurements were synchronized to the time point of the first YSI measurement <70 mg/dL after the initial glucose level peak. Abbreviations: CGM, continuous glucose monitoring; FL3, FreeStyle Libre 3 CGM system; DG7, Dexcom G7 CGM system; MSP, Medtronic Simplera CGM system; YSI, YSI 2300 STAT PLUS laboratory analyzer; INT, COBAS INTEGRA 400 plus Analyzer; CNX, Contour Next blood glucose monitoring system.
Figure 4.
Figure 4.
Stability of CGM sensors in terms of MARD (panel a) and bias (panel b) with respect to free-living CNX measurements stratified according to the time after sensor insertion. The dashed lines indicate aggregate results for this data set over the entire study duration. Abbreviations: FL3, FreeStyle Libre 3 CGM system; DG7, Dexcom G7 CGM system; MSP, Medtronic Simplera CGM system; MARD, mean absolute relative difference; CNX, Contour Next blood glucose monitoring system.
Figure 5.
Figure 5.
Kaplan-Meier survival plot. The vertical lines indicate sensors removed prior to the end of their lifetime as part of the protocol (censoring). Abbreviations: FL3, FreeStyle Libre 3 CGM system; DG7, Dexcom G7 CGM system; MSP, Medtronic Simplera CGM system.
Figure 6.
Figure 6.
Summary results of selected items of the user satisfaction questionnaire. Abbreviations: FL3, FreeStyle Libre 3 CGM system; DG7, Dexcom G7 CGM system; MSP, Medtronic Simplera CGM system.
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