A Real-World Prospective Study of the Safety and Effectiveness of the Loop Open Source Automated Insulin Delivery System

Abstract

Objective: To evaluate the safety and effectiveness of the Loop Do-It-Yourself automated insulin delivery system. Research Design and Methods: A prospective real-world observational study was conducted, which included 558 adults and children (age range 1-71 years, mean HbA1c 6.8% ± 1.0%) who initiated Loop either on their own or with community-developed resources and provided data for 6 months. Results: Mean time-in-range 70-180 mg/dL (TIR) increased from 67% ± 16% at baseline (before starting Loop) to 73% ± 13% during the 6 months (mean change from baseline 6.6%, 95% confidence interval [CI] 5.9%-7.4%; P < 0.001). TIR increased in both adults and children, across the full range of baseline HbA1c, and in participants with both high- and moderate-income levels. Median time <54 mg/dL was 0.40% at baseline and changed by -0.05% (95% CI -0.09% to -0.03%, P < 0.001). Mean HbA1c was 6.8% ± 1.0% at baseline and decreased to 6.5% ± 0.8% after 6 months (mean difference = -0.33%, 95% CI -0.40% to -0.26%, P < 0.001). The incidence rate of reported severe hypoglycemia events was 18.7 per 100 person-years, a reduction from the incidence rate of 181 per 100 person-years during the 3 months before the study. Among the 481 users providing Loop data at 6 months, median continuous glucose monitoring use was 96% (interquartile range [IQR] 91%-98%) and median time Loop modulating basal insulin was at least 83% (IQR 73%-88%). Conclusions: The Loop open source system can be initiated with community-developed resources and used safely and effectively by adults and children with type 1 diabetes.

Keywords: Automated insulin delivery; Closed-loop control; Continuous glucose monitors; Safety; Type 1 diabetes.

FIG. 1.

(A) Time in range 70–180 mg/dL in the first 4 weeks after Loop initiation. (B) Cumulative distribution of time in range at baseline and follow-up. Solid blue line represents baseline. Solid red line represents months 1–6.

FIG. 2.

(A) Time in range 70–180 mg/dL over a 24 h period. Solid blue line represents median baseline. Solid blue dot represents mean baseline. Shaded blue represents baseline quartiles. Solid red line represents median months 1–6. Solid red dot represents mean months 1–6. Shaded red represents months 1–6 quartiles. (B) Time <54 mg/dL over a 24 h period. Solid blue line represents median baseline. Solid blue dot represents mean baseline. Shaded blue represents baseline quartiles. Solid red line represents median months 1–6. Solid red dot represents mean months 1–6. Shaded red represents months 1–6 quartiles.