Objective: To describe the real world impact of the 670G Hybrid Closed Loop (HCL) system on glucose control in pediatric patients with type 1 diabetes (T1D).
Methods: Patients starting the 670G were recruited to participate in a 12-month observational study. Data on 670G use and glycemic outcomes were obtained from pump downloads and chart review as part of routine clinical care. Descriptive statistics are reported as medians (25th%ile, 75th%ile).
Results: Nineteen pediatric patients (14 y (11.7, 17.4); 53% F) with 32 days (26, 44) of 670G data were included. T1D duration was 7 years (3, 9) and HbA1C was 8.5% (7.9, 9.6). Patients spent 70% (35, 85) of each week in HCL. System exits from HCL mode (auto mode) to standard pump mode (manual mode) occurred 0.64 times/day (0.5, 1.05), primarily due to hyperglycemia. Sensor glucose time in target range (70-180 mg/dl) was 60% (50, 64) with 1% of sensor glucose values ≤70 mg/dl. Increased time spent in HCL was correlated with reduced mean sensor glucose and standard deviation of glucose, and increased time in target range (Table).
Conclusions: Youth using the 670G in clinical care were able to stay in HCL most of the time in the initial weeks of system use. HCL use may improve glucose control for pediatric patients with T1D. Data collection is ongoing and will elucidate the impact of the 670G on glycemic control longitudinally and describe patient use of the system in real-world conditions.
Correlation of % time in HCL 'auto mode' with glucose variables
| Variable | Spearman Correlation Coefficient | p-value |
| % time sensor values 70-180 mg/dl | 0.67 | 0.002 |
| Mean sensor glucose value | -0.60 | 0.007 |
| % time sensor <54 mg/dl | -0.049 | 0.84 |
| % time sensor values 54-69 mg/dl | 0.17 | 0.50 |
| % time sensor values >250 mg/dl | -0.67 | 0.002 |
| Standard deviation of sensor glucose values | -0.54 | 0.02 |
| Variable | Spearman Correlation Coefficient | p-value |
| % time sensor values 70-180 mg/dl | 0.67 | 0.002 |
| Mean sensor glucose value | -0.60 | 0.007 |
| % time sensor <54 mg/dl | -0.049 | 0.84 |
| % time sensor values 54-69 mg/dl | 0.17 | 0.50 |
| % time sensor values >250 mg/dl | -0.67 | 0.002 |
| Standard deviation of sensor glucose values | -0.54 | 0.02 |
C. Berget: None. L.H. Messer: Other Relationship; Self; Medtronic MiniMed, Inc.. L. Pyle: None. E. Westfall: None. G.P. Forlenza: Advisory Panel; Self; Dexcom, Inc.. Research Support; Self; Medtronic, Tandem Diabetes Care, Inc., Insulet Corporation, Dexcom, Inc., Novo Nordisk Inc., Bigfoot Biomedical. K.A. Driscoll: None.
