Real-World Implementation of Hybrid Closed-Loop (HCL) Insulin Delivery

Objective: Clinical trials demonstrate improved glycemic control with HCL insulin delivery systems, yet limited real-world data exists substantiating these findings. Data from the inaugural cohort of patients initiating a HCL system (Medtronic 670G) at a university medical center was used to examine real-world utilization, adherence, and glycemic control over the first 6-12 weeks of pump use.

Research Design and Methods: Data from 35 patients with type 1 diabetes (22-72 years of age) were obtained from insulin pump downloads at 4 time points: previous insulin pump, HCL start in manual-mode, 2-weeks after auto-mode transition, and between 6-12 weeks after HCL start. In person training by certified diabetes educators was performed for manual-mode, sensor initiation, and auto-mode with phone and electronic messaging following initiation of auto-mode.

Results: A total of 46 patients received HCL between June 1 and December 31 of 2017. Of these, 7 patients did not have sensors allowing them to initiate HCL, 3 did not have a 6-12 week download, and 1 never transitioned into auto-mode. Mean self-monitoring blood glucose (SMBG) per day increased from 5.15 baseline to 6.49 at 6-12 weeks (p<0.05) with 3.26 sensor calibrations per day. Time in auto-mode was 79.3% at 2 weeks, and 71.7% by 6-12 weeks with 82% of patients spending >50% of time in auto-mode. Over the 14-day final download there were 8.2 auto-mode exits. Time in target was 65.5% in manual-mode, 73.4% at 2-weeks (p=0.09), and 71.7% by 6-12 weeks (p=0.06). HbA_1C decreased 0.51% (p=0.02), total daily dose increased (p=0.027), while basal-to-bolus ratio did not change over the study period. Baseline mean SMBG and HbA_1C, but not basal:bolus ratio, bolus calculator use, or bolus frequency, were significant predictors of time in auto-mode and time-in-target at 6-12 weeks.

Conclusions: These data illustrate real-world implementation of HCL technology within a major medical center. Patients initiating HCL achieved acceptable time-in-auto mode and time-in-target range.