Hybrid closed loop system delivers glycaemic benefits: Australian RCT

An Australian study has shown that a hybrid closed-loop (HCL) insulin delivery system results in better glycaemic outcomes in people with type 1 diabetes (T1D) compared to user determined insulin dosing and self-monitoring of blood glucose.

The results come from a six-month randomised controlled trial involving 120 adults with T1D at seven Australian centres, half of whom used the Medtronic 670G system with a glucose sensor (Enlite 3) and transmitter (GST3c MiniLink) to automate basal insulin delivery.

For the primary outcome of Time in Range (TIR), the HCL users ( n=61) showed an improvement from 55% at baseline to 70% at 26 weeks, compared to no change in a control group (n=59).

Secondary glucose outcomes also favoured the HCL user group, with less time in each of the low and high glucose ranges, lower mean glucose, lower HbA1c, and higher 1,5-anhydroglucitol levels compared with standard therapy.

People who used the HCL system showed a modest reduction from 7.4% to 7.0% in HbA1c during the trial, compared to no change in the control group.

There was a larger mean decrease in proportional basal insulin use with HCL (-5.4% vs. control 1.9%) and a larger increase in proportional bolus insulin use (HCL 5.0% vs. control -1.6%) by 26 weeks.

Users of the HCL system also showed improvement in some psychosocial outcomes, such as diabetes-related satisfaction and wellbeing, but there were no changes in treatment satisfaction, diabetes distress, sleep or cognition.

There were 17 serious adverse events in the HCL group compared to 13 in the control group.  The nine adverse events related to the HCL device included four episodes of severe hypoglycemia.

Writing in Diabetes Care, lead investigators Dr Sybil McCauley and Professor David O’Neal of St Vincent’s Hospital, Melbourne, said there was no published evidence from a randomised controlled trial for the Medtronic HCL system and the Australian trial differed from uncontrolled studies in using self-monitoring of blood glucose as a comparator rather than sensor-augmented pump therapy.

They said the 15% difference in TIR with the HCL device would translate to 3.6 extra hours per day within the healthy glucose range for users compared with the control group, and noted there was a relatively greater improvement in overnight glycaemia.

The study authors said the trial had shown that the HCL system could deliver clinically meaningful improvements in people with T1D, including people who were not currently using technologies such as insulin pumps or continuous glucose monitors.

This “refutes prior assumptions made by clinicians as well as experiences of participants in a shorter trial, some of whom expressed that HCL could be “too big a step”,” they wrote.

“For most people living with type 1 diabetes globally, this trial demonstrates that HCL is feasible, acceptable, and advantageous,” they concluded.

However they acknowledged that the trial had been done in a select group of patients who received intensive support, and that people using the HCL system required several healthcare visits for training in how to use the device. Therefore further evaluation is needed of models of care to support the introduction of the HCL system, they said.

A podcast featuring Professor O’Neal discussing hybrid closed loop systems will be available on the limbic next week.

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