Switching from Suspend-Before-Low Insulin Pump Technology to a Hybrid Closed-Loop System Improves Glucose Control and Reduces Glucose Variability: A Retrospective Observational Case-Control Study

Abstract

There are no data whether hybrid closed-loop (HCL) systems are superior to sensor-augmented pump (SAP) therapy with predictive low glucose suspend (PLGS) feature in improving glucose control. Aim of our study was to evaluate the effect on metabolic control and glucose variability of the switch from SAP therapy with PLGS to a HCL system in type 1 diabetic individuals. Forty adults with type 1 diabetes, who had been using SAP therapy with PLGS feature (Minimed 640G; Medtronic, Northridge, CA) for at least 12 months were evaluated in a 6-month case-control observational retrospective study. Twenty subjects who consecutively switched from Minimed 640G to a HCL system (Minimed 670G; Medtronic) (670G group) were compared with a control group consisting of 20 subjects who continued with the MiniMed 640G pump (640G group) matched for age, gender, and HbA_1c. At the end of the study there was a significant reduction in average HbA_1c levels (-4.9 ± 6.4 mmol/mol [-0.4% ± 0.6%], P < 0.01), sensor glucose concentrations (-15.4 ± 17.7 mg/dL, P < 0.005), coefficient of variation of sensor glucose concentrations (-3.8% ± 3.6%, P < 0.01), percentage time spent in both hyperglycemic range 181-250 mg/dL (-5.1% ± 4.5%, P < 0.05), and >250 mg/dL (-6.1% ± 6.9%, P < 0.05) in the 670G group, whereas they remained unchanged in the 640G group. Percentage of time spent in euglycemic range significantly increased (11.6% ± 8.3%, P < 0.005) only in the 670G group. There was no change in time spent in hypoglycemic range in both groups. In adults with type 1 diabetes, switching from a 640G to a 670G system significantly improved glucose control and reduced glucose variability, thus reaching in most cases the recommended targets for time spent in euglycemic and hyperglycemic ranges without increasing the risk of hypoglycemia.

Keywords: Hybrid closed-loop system; Predictive low glucose suspend; Sensor-augmented pump; Type 1 diabetes mellitus.