Safety of outpatient closed-loop control: first randomized crossover trials of a wearable artificial pancreas

Diabetes Care. 2014 Jul;37(7):1789-96. doi: 10.2337/dc13-2076. Epub 2014 Jun 14.


Objective: We estimate the effect size of hypoglycemia risk reduction on closed-loop control (CLC) versus open-loop (OL) sensor-augmented insulin pump therapy in supervised outpatient setting.

Research design and methods: Twenty patients with type 1 diabetes initiated the study at the Universities of Virginia, Padova, and Montpellier and Sansum Diabetes Research Institute; 18 completed the entire protocol. Each patient participated in two 40-h outpatient sessions, CLC versus OL, in randomized order. Sensor (Dexcom G4) and insulin pump (Tandem t:slim) were connected to Diabetes Assistant (DiAs)-a smartphone artificial pancreas platform. The patient operated the system through the DiAs user interface during both CLC and OL; study personnel supervised on site and monitored DiAs remotely. There were no dietary restrictions; 45-min walks in town and restaurant dinners were included in both CLC and OL; alcohol was permitted.

Results: The primary outcome-reduction in risk for hypoglycemia as measured by the low blood glucose (BG) index (LGBI)-resulted in an effect size of 0.64, P = 0.003, with a twofold reduction of hypoglycemia requiring carbohydrate treatment: 1.2 vs. 2.4 episodes/session on CLC versus OL (P = 0.02). This was accompanied by a slight decrease in percentage of time in the target range of 3.9-10 mmol/L (66.1 vs. 70.7%) and increase in mean BG (8.9 vs. 8.4 mmol/L; P = 0.04) on CLC versus OL.

Conclusions: CLC running on a smartphone (DiAs) in outpatient conditions reduced hypoglycemia and hypoglycemia treatments when compared with sensor-augmented pump therapy. This was accompanied by marginal increase in average glycemia resulting from a possible overemphasis on hypoglycemia safety.

Trial registration: NCT01714505 NCT01727817 NCT01742741.

Publication types

  • Comparative Study
  • Randomized Controlled Trial
  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Blood Glucose / drug effects
  • Blood Glucose Self-Monitoring
  • Cell Phone
  • Cross-Over Studies
  • Diabetes Mellitus, Type 1 / blood
  • Diabetes Mellitus, Type 1 / drug therapy*
  • Female
  • Humans
  • Hypoglycemia / chemically induced
  • Hypoglycemic Agents / administration & dosage*
  • Hypoglycemic Agents / adverse effects
  • Hypoglycemic Agents / therapeutic use
  • Insulin / administration & dosage*
  • Insulin / adverse effects
  • Insulin / therapeutic use
  • Insulin Infusion Systems
  • Male
  • Middle Aged
  • Outpatients
  • Pancreas, Artificial* / adverse effects
  • Treatment Outcome


  • Blood Glucose
  • Hypoglycemic Agents
  • Insulin

Associated data