medwireNews: Research shows that the use of an artificial pancreas (AP) system helps to compensate for omission and underestimation of insulin boluses in adolescents with Type 1 diabetes.

However, the researchers stress that the system cannot replace active diabetes management.

Sixteen adolescents, who were aged between 13 and 17 years and using an insulin pump, participated in the randomised, crossover trial, during which they had a snack without first taking an insulin bolus and then ate lunch after a bolus that was only 75% of that required for the carbohydrate content of the meal.

In one treatment phase, they used their home insulin pump on usual basal rates and in the other phase they used a closed-loop AP, run via an Android smartphone.

“Perhaps the most striking finding of the study overall was the extent of hyperglycemia during both treatment phases following insulin omission,” say Marc Breton (University of Virginia, Charlottesville, USA) and co-workers.

During the 4 hours following the unannounced snack, the participants’ blood glucose levels remained within a near-normal range (70–180 mg/mL) for 45.07% of the time during the AP treatment phase versus 21.31% during the usual treatment phase. This did not come at the expense of more hypoglycaemia, which occurred at an average of 0.06 versus 0.13 hypoglycaemic events per person during the closed-loop and usual care phases, respectively.

Although the closed-loop system significantly reduced the time spent in hyperglycaemia, it was still “suboptimal by diabetes standards”, says the team.

“This underscores that even in the setting of the AP overall [blood glucose] control will be improved by accurate meal announcement”, write Breton et al in Pediatric Diabetes. “Current AP systems appear likely to lower [blood glucose] values but will function better in the context of active diabetes management.”

The findings were similar for lunch with a reduced insulin bolus; during the 4 hours after lunch, blood glucose was near-normal for 42.32% of the time with closed-loop treatment versus 16.88% with usual care. There were no hypoglycaemic events in either group after lunch.

The overall amount of insulin delivered was significantly higher in the closed-loop phase than the usual care phase, at 19.0 versus 17.1 U. The largest increase, of 72%, was in the period after the unannounced snack, at 6.9 versus 4.0 U.

The team says: “To our knowledge, this represents the first evidence of an AP system improving [blood glucose] following insulin omission for carbohydrate intake among adolescents – the age group with highest average HbA1c [glycated haemoglobin] levels and potentially the most to gain from such an intervention.”

By Eleanor McDermid, Senior medwireNews Reporter

Pediatr Diabetes 2014; Advance online publication

Free abstract