One Year Clinical Experience of the First Commercial Hybrid Closed-Loop System

Abstract

Objective: In September 2016, the U.S. Food and Drug Administration approved the Medtronic 670G "hybrid" closed-loop system. In Auto Mode, this system automatically controls basal insulin delivery based on continuous glucose monitoring data but requires users to enter carbohydrates and blood glucose for boluses. To track real-world experience with this first commercial closed-loop device, we prospectively followed pediatric and adult patients starting the 670G system.

Research design and methods: This was a 1-year prospective observational study of patients with type 1 diabetes starting the 670G system between May 2017 and May 2018 in clinic.

Results: Of the total of 84 patients who received 670G and consented, 5 never returned for follow-up, with 79 (aged 9-61 years) providing data at 1 week and 3, 6, 9, and/or 12 months after Auto Mode initiation. For the 86% (68 out of 79) with 1-week data, 99% (67 out of 68) successfully started. By 3 months, at least 28% (22 out of 79) had stopped using Auto Mode; at 6 months, 34% (27 out of 79); at 9 months, 35% (28 out of 79); and by 12 months, 33% (26 out of 79). The primary reason for continuing Auto Mode was desire for increased time in range. Reasons for discontinuation included sensor issues in 62% (16 out of 26), problems obtaining supplies in 12% (3 out of 26), hypoglycemia fear in 12% (3 out of 26), multiple daily injection preference in 8% (2 out of 26), and sports in 8% (2 out of 26). At all visits, there was a significant correlation between hemoglobin A1c (HbA1c) and Auto Mode utilization.

Conclusions: While Auto Mode utilization correlates with improved glycemic control, a focus on usability and human factors is necessary to ensure use of Auto Mode. Alarms and sensor calibration are a major patient concern, which future technology should alleviate.

Trial registration: ClinicalTrials.gov NCT03017482.

© 2019 by the American Diabetes Association.

Figures

Figure 1

Violin plot reflecting percentage of time in Auto Mode by time of follow-up, with the number of participants with available data noted. For the available data, usage of Auto Mode diminishes over time. At 1 week, mean 74% and median 82%; at 3 months, mean 50% and median 66%; at 6 months, mean 44% and median 52%; at 9 months, mean 37% and median 31%; and at 12 months, mean 35% and median 17%.

Figure 2

Scatter plots of percentage of time in Auto Mode vs. HbA1c by time of follow-up. Linear regression demonstrates significant correlation at every time point. One-week data are constructed from baseline HbA1c compared with Auto Mode use 1 week after initiation of the 670G system.