Objective: In September 2016, the FDA approved the Medtronic 670G “hybrid” closed-loop system. In “Auto Mode,” this system automatically controls basal insulin delivery based on CGM data, but requires users to enter carbohydrate intake and blood sugar for boluses. Studies show improved time in range associated with the use of Auto Mode. In an effort to track our real-world experience with this first commercial closed-loop device, we followed pediatric and adult patients placed on the 670G.

Methods: This was a 1-year prospective observational study, recruiting 5/2017-9/2018, of patients with type 1 diabetes, ≥7 years, starting the 670G system.

Results: 84 patients started on the 670G (range 9-61 years), 26 (31%) were <18 years. Figure 1 shows a violin plot of percentage time in Auto Mode at each visit. Upon starting Auto Mode, 96% of participants continued for the first week. For those with available data by 3 months 22% stopped using Auto Mode, at 6 months 30%, at 9 months 43% and by 12 months 50% (70% <18, 40% ≥18). Reasons for discontinuation included CGM issues, too many alarms and lack of control. At 6 months there was a significant correlation between improved A1c and time in Auto Mode (r = 0.4, p = 0.01).

Conclusions: While use of closed-loop technology correlates with improved glycemic control, a focus on usability and human factors is necessary to ensure patients stay on treatment. Alarms and sensor calibration are a major patient concern, which next generation technology should alleviate.


R. Lal: Consultant; Self; Abbott. M. Basina: None. D.M. Maahs: Advisory Panel; Self; Novo Nordisk Inc. Consultant; Self; Abbott, Sanofi. Research Support; Self; Dexcom, Inc., Tandem Diabetes Care. B.A. Buckingham: Advisory Panel; Self; ConvaTec Inc., Novo Nordisk Inc., Profusa, Inc. Consultant; Self; Medtronic MiniMed, Inc. Research Support; Self; Beta Bionics, ConvaTec Inc., Dexcom, Inc., Insulet Corporation, Medtronic MiniMed, Inc., Tandem Diabetes Care. Other Relationship; Self; Insulet Corporation, Tandem Diabetes Care. K.K. Hood: Consultant; Self; Lilly Diabetes. Research Support; Self; Dexcom, Inc. Speaker's Bureau; Self; Johnson & Johnson Diabetes Institute. B.P. Conrad: None. J. Leverenz: None. A. Chmielewski: None. K. Peterson: None. D. Wilson: Advisory Panel; Self; Tolerion, Inc. Research Support; Self; Beta Bionics, Dexcom, Inc., Medtronic.


National Institute of Diabetes and Digestive and Kidney Diseases (T32DK007217); Seiler Fund

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