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16-10-2019 | Diabetes | News | Article

iDCL trial shows sustained time in range improvement with hybrid closed-loop delivery

medwireNews: People with type 1 diabetes using the Tandem Control-IQ hybrid closed-loop insulin delivery system spent significantly more time within their target blood glucose range than people using a sensor-augmented insulin pump during 6 months of use in the iDCL trial.

The Tandem Control-IQ system comprises the t:slim X2 insulin pump, the Dexcom G6 continuous glucose monitor, and a glucose control algorithm originally developed at the University of Virginia.

As reported in The New England Journal of Medicine, during 6 months of use the 112 study participants randomly assigned to use this system spent an average 71% of their time with blood glucose levels between 70 and 180 mg/dL (3.9 and 10.0 mmol/L).

This was an 11 percentage point improvement over the average of 59% in the 56 control group participants, who used a sensor-augmented insulin pump. It was also a 10 percentage point improvement over a 2-week baseline period using an insulin pump and continuous glucose monitor; the control group had no improvement relative to this baseline period.

In a linked editorial, Daniela Bruttomesso (University of Padua, Italy) describes the findings as “impressive and clinically relevant,” given the demonstrable positive effect of better glycemic control on the risk for diabetic complications.

However, she highlights that the closed-loop system was not tested against a pump that suspends insulin delivery when hypoglycemia is imminent, which could have resulted in a smaller difference between the two groups.

The 11 percentage point difference amounted to people in the closed-loop group spending an additional 2.6 hours per day within the target range and the effect was evident from within the first month of use.

In the closed-loop group, blood glucose was within the target range for an average 70%of the daytime and 76% of the night. For the control group it was 59% for both.

The study participants were aged at least 14 years (average 33 years, with 28–30% <18 years), the majority were already using insulin pumps and continuous glucose monitoring, and their average glycated hemoglobin (HbA1c) level at screening was 7.6% (60 mmol/mol). There was no restriction on HbA1c at entry, so about a third had levels below 7.0% (53 mmol/mol) and around 4% had levels of 9.0% (75 mmol/mol) or higher.

Closed-loop control significantly improved time in both hyperglycemia and hypoglycemia versus sensor-augmented pump use, by a respective 10.0 and 0.88 percentage points, with the closed-loop group spending an average of 27% and 1.58% of time in these states, compared with 38% and 2.25%, respectively, for the control group.

Adverse events were mostly hyperglycemia or ketosis events, with 13 events in the closed-loop group (including one episode of diabetic ketoacidosis) and two in the control group. Boris Kovatchev (University of Virginia, Charlottesville, USA) and co-researchers attributed “almost all” of these events to infusion set failure.

By Eleanor McDermid

medwireNews is an independent medical news service provided by Springer Healthcare. © 2019 Springer Healthcare part of the Springer Nature group

N Engl J Med 2019; 381: 1707–1717
N Engl J Med 2019; doi:10.1056/NEJMe1912822