Study authors Sue A. Brown, MD, and Boris P. Kovatchev, PhD, along with their team from the Jaeb Center for Health Research, Tampa, Florida (the coordinating center for the multicenter study), examined the percentage of time that blood-glucose values of subjects were within the established target range of 70 to 180 mg per deciliter as recorded by continuous glucose monitoring. The team assigned a total of 168 subjects with type 1 diabetes to receive either the sensor-augmented pump (control group, n = 56) or the closed-loop system (treatment group, n = 112) during the 6-month trial. The glycated hemoglobin level ranged from 5.4% to 10.6%, and all patients completed the trial. 

In this International Diabetes Closed-Loop Study, the team determined that the average percent time within target blood glucose range increased in the closed-loop group from 61% ± 17% (±SD) at baseline to 71% ± 12% during the 6 months and remained unchanged at 59% ±1 4% in the control group (95% CI, 9-14; P <.001). Although it was not a primary outcome, the team noted that the percentage of time that glucose values were greater than 180 mg per deciliter, along with percentage of time that the glucose values were less than 70 mg per deciliter or less than 54 mg per deciliter, also favored the closed-loop system. No serious hypoglycemic events were reported in either the treatment group or the control group; however, one episode of diabetic ketoacidosis was reported in the closed-loop group.

“This artificial pancreas system has several unique features that improve glucose control beyond what is achievable using traditional methods,” said Dr. Kovatchev. “In particular, there is a special safety module dedicated to prevention of hypoglycemia, and there is gradually intensified control overnight to achieve near-normal blood sugar levels every morning.” 

According to Guillermo Arreaza-Rubín, MD, director of the National Institute of Diabetes and Digestive and Kidney Diseases’ Diabetes Technology Program and project scientist for the study, “Testing the safety and effectiveness of new technologies in real-world settings is critical to prove the usability of these systems by people with diabetes to achieve a better daily control of their blood glucose levels.” 

Researchers concluded that this 6-month trial involving patients with type 1 diabetes supports the use of a closed-loop system due to the findings of the “greater percentage of time spent in a target glycemic range than the use of a sensor-augmented insulin pump” and that the system improved patients’ control over blood glucose during the day and overnight, with the latter being the more serious complication if values drop to dangerous levels during sleep. 

The International Diabetes Closed-Loop Study involves five separate artificial-pancreas clinical protocols implemented by 10 research centers, including the University of Colorado Anschutz Medical Campus. This 6-month study was the third phase in the series of trials. It was conducted with participants living their usual day-to-day lives, so the researchers could best understand how the system works in typical daily routines.

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