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wear with the exception of the first day of wear, which had the lowest accuracy (Consensus EGA showed 72.0% in Zone A for Day 1 compared with 88.4% in Zone A for Day 2). This may be due in part to the body’s natural inflammatory re- sponse to sensor insertion, which has been shown to affect glucose concentration in interstitial fluid.26 In the present study, the System’s sensor did not show any marked differences in accuracy outcomes relative to BMI, age, type of diabetes, clinical site, insulin administration, or hemoglobin A1c. In comparison, the accuracy (Clarke EGA) of the FreeStyle NavigatorÒ sensor (Abbott Diabetes Care), which used a sensor with the same wired enzyme technology, as reported by Weinstein et al.,27 did not differ as a function of age, sex, ethnicity, years since diagnosis of diabetes, or sensors worn on either the arm or abdomen but differed depending on the subject’s BMI. The percentage of readings in Zone A (Clarke EGA) for participants who had a BMI of <25 kg/m2 was 78.8% compared with 84.4% for participants with a BMI of >30 kg/m2 , which the authors suggested could have been attributed to differences in blood flow relative to subcutaneous adipose tissue thickness. The present study with the System included a broad range of BMI (18.7– 47.2 kg/m2 ), which did not affect the sensor accuracy. Place- ment of the System’s sensor was on both arms for each subject, and future studies could evaluate the effects of sensor accuracy in different locations on the body. These results have clinical implications for individuals with diabetes and for the clinicians who treat them. Several randomized controlled studies have revealed better hemo- globin A1c outcomes associated with the frequency of sensor wear.28–32 Thus, a sensor with a longer wear period that does not require fingerstick calibration with its associated burden and pain may support more frequent sensor use with im- proved glycemic outcomes. This system with no additional fingerstick may also benefit groups that have demonstrated poor adoption of persistent sensor use. The System’s sensor provides a broader interval and volume of measurements, including day and night readings, which can be used to evaluate glucose patterns and trends. In comparison, capillary BG readings provide single, intermittent measure- ments, which may not capture intervals of extreme variability or nocturnal events. In a recent study, it was demonstrated that the use of continuous glucose monitoring with or without alarms reduces time spent outside glucose targets compared with self-monitoring of BG.13 The System provides the user with the current glucose result, glucose pattern, and trend in- formation on the display of the hand-held reader when the sensor is scanned. This type of monitoring system may benefit individuals who have ceased sensor use due to alarm fatigue, becoming overwhelmed by alarms.11 Limitations of the cur- rent study are single body site used for data collection, limited venous reference data over the 14-day wear due to practical limitation of obtaining blood, and a limited number of sensor lots used in the study. Further research is needed to evaluate whether the System could provide additional benefits such as improvement in glycemic outcomes with continued use over time, as well as improved compliance with sensor wear. Conclusions In this prospective study, the performance of the factor- only calibrated FreeStyle Libre Flash glucose monitoring system was demonstrated by the accuracy of sensor readings and the stability of accurate readings over 14 days of use. The accuracy of the System was unaffected by subject charac- teristics, making it suitable for a broad range of individuals. Under normal conditions, the System provides an easy to use and comfortable sensor wear experience for up to 14 days without the need for fingerstick measurements. It is antici- pated that the provision of comprehensive glucose data for up to 14 days with reduced pain and burden for the end user will support enhanced diabetes management. Acknowledgments The authors thank Joe Bugler for his critical review of the manuscript and Zoe K. Welsh for graphical and statistical support. Suzie Webster (ConsignMed, Inc.) provided medical writing and editorial assistance. Funding for this study was provided by Abbott Diabetes Care. Author Disclosure Statement S.A. is an employee of Abbott Diabetes Care. M.P.C., L.J.K., T.B., and B.W.B. were the study investigators and declare that no competing financial interests exist. References 1. Freckmann G, Pleus S, Link M, Zshornack E, Klotzer H, Haug C: Performance evaluation of three continuous glu- cose monitoring systems: comparison of six sensors per subject in parallel. J Diabetes Sci Techol 2013;7:842–853. 2. Pfu¨tzner A, Mitri M, Musholt PB, Sachsenheimer D, Borchert M, Yap A, Forst T: Clinical assessment of the accuracy of blood glucose measurement devices. Curr Med Res Opin 2012;28:525–531. 3. Freckmann G, Baumstark A, Schmid C, Pleus S, Link M, Haug C: Evaluation of 12 blood glucose monitoring sys- tems for self-testing: system accuracy and measurement reproducibility. Diabetes Technol Ther 2014;16:113–122. 4. Klaff LJ, Brazg R, Hughes K, Tideman AM, Schachner HC, Stenger P, Pardo S, Dunne N, Parkes JL: Accuracy evaluation of Contour Next compared with five blood glucose monitoring systems across a wide range of blood glucose concentrations occurring in a clinical research setting. Diabetes Technol Ther 2015;17:8–15. 5. Thomas LE, Kane MP, Bakst G, Busch RS, Hamilton RA, Abelseth JM: A glucose meter accuracy and precision comparison: the FreeStyle Flash versus the Accu-Chek Advantage, Accu-Chek Compact Plus, Ascensia Contour, and the BD Logic. Diabetes Technol Ther 2008;10:102– 110. 6. Damiano E, El-Khatib F, Zheng H, Nathan D, Russell S: A comparative effectiveness analysis of three continuous glucose monitors. Diabetes Care 2013;36:251–259. 7. Damiano E, McKeon K, El-Khatib F, Zheng H, Nathan D, Russell S: A comparative effectiveness analysis of three continuous glucose monitors: the Navigator, G4 Platinum, and Enlite. J Diabetes Sci Technol 2014;8:699–708. 8. Matuleviciene V, Joseph J, Andelin M, Hirsch I, Attvall S, Pivodic A, Dahlqvist, Klonoff D, Haraldsson B, Lind M: A clinical trial of the accuracy and treatment experience of the Dexcom G4 sensor (Dexcom G4 system) and Enlite sensor (Guardian REAL-Time system) tested simulta- neously in ambulatory patients with type 1 diabetes. Dia- betes Technol Ther 2014;16:759–767. FACTORY-CALIBRATED FLASH GLUCOSE MONITORING 7

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