1009-P: Glucose Outcomes in Adult Patients with Type 1 Diabetes on a Hybrid Closed-Loop System: A Single Center Study

Objectives: Medtronic’s 670G insulin pump was the first to incorporate automatic basal insulin delivery based on input from CGM data, a setting called Smart Guard Automode. We assessed glycemic control (A1c) in 52 patients with T1DM who used the Medtronic 670G hybrid closed loop system and started Automode from 2017 to 2019. Our goal was to determine the effects of Automode use on A1c over time. The average age was 46.4 ± 12.3 years, 53.4% male and 78.8% Caucasian. The average age at diagnosis was 19.1 ± 13.5 years and duration was 27.3 ± 14.6 years. Diabetic complications were present in 55.8% patients.

Methods: Patients were divided into two groups depending on whether their A1c was above or below the mean baseline A1c for the cohort; 26 patients had A1c ≤7.6% (mean 6.9 ± 0.4, range 6.2 to 7.6, Group 1) and 26 had A1c >7.6 (mean 8.3 ± 0.5, range 7.7-9.3, Group 2). Follow-up A1c was assessed a mean of 17.1 ± 7.3 months after beginning Automode.

Results: 1. The average A1c of the 52 patients prior to initiating Automode was 7.6 ± 0.8 (range 6.2-9.3). Follow-up A1c for the cohort was 7.5 ± 0.67 (range 6.3-9). 2. At follow-up, Group 1’s mean A1c remained about the same at 7.1 ± 0.5 (range 6.3-8.4) whereas Group 2’s mean A1c was reduced to 7.8 ± 0.6 (range 6.9-9). Females displayed greater A1c improvement (-0.2 ± 0.6, range -1.2-9) than males (-0.1 ± 0.6, range -1.4-0.7) and those with complications showed greater A1c improvement (-0.2 ± 0.5, range -1.2-0.7) than those without (-0.1 ± 0.6, range -1.4-0.9). Additionally, the 27 patients with duration of diabetes ≥25 years showed greater improvement in A1c (-0.2 ± 0.5, range -1.2-0.7) than those with duration <25 years (-0.06 ± 0.6, range -1.4-0.9).

Conclusion: Patients with worse baseline glucose control (mean 8.3 ± 0.5) had improved A1c using the hybrid closed loop system compared to patients with higher A1c (mean 6.9 ± 0.4). We also observed a nonsignificant trend towards improvements in females, patients with complications and longer duration of diabetes.