Accuracy of Continuous Glucose Monitoring During Three Closed-Loop Home Studies Under Free-Living Conditions

Diabetes Technol Ther. 2015 Nov;17(11):801-7. doi: 10.1089/dia.2015.0062. Epub 2015 Aug 4.

Abstract

Objectives: Closed-loop (CL) systems modulate insulin delivery based on glucose levels measured by a continuous glucose monitor (CGM). Accuracy of the CGM affects CL performance and safety. We evaluated the accuracy of the Freestyle Navigator(®) II CGM (Abbott Diabetes Care, Alameda, CA) during three unsupervised, randomized, open-label, crossover home CL studies.

Materials and methods: Paired CGM and capillary glucose values (10,597 pairs) were collected from 57 participants with type 1 diabetes (41 adults [mean±SD age, 39±12 years; mean±SD hemoglobin A1c, 7.9±0.8%] recruited at five centers and 16 adolescents [mean±SD age, 15.6±3.6 years; mean±SD hemoglobin A1c, 8.1±0.8%] recruited at two centers). Numerical accuracy was assessed by absolute relative difference (ARD) and International Organization for Standardization (ISO) 15197:2013 15/15% limits, and clinical accuracy was assessed by Clarke error grid analysis.

Results: Total duration of sensor use was 2,002 days (48,052 h). Overall sensor accuracy for the capillary glucose range (1.1-27.8 mmol/L) showed mean±SD and median (interquartile range) ARD of 14.2±15.5% and 10.0% (4.5%, 18.4%), respectively. Lowest mean ARD was observed in the hyperglycemic range (9.8±8.8%). Over 95% of pairs were in combined Clarke error grid Zones A and B (A, 80.1%, B, 16.2%). Overall, 70.0% of the sensor readings satisfied ISO criteria. Mean ARD was consistent (12.3%; 95% of the values fall within ±3.7%) and not different between participants (P=0.06) within the euglycemic and hyperglycemic range, when CL is actively modulating insulin delivery.

Conclusions: Consistent accuracy of the CGM within the euglycemic-hyperglycemic range using the Freestyle Navigator II was observed and supports its use in home CL studies. Our results may contribute toward establishing normative CGM performance criteria for unsupervised home use of CL.

Trial registration: ClinicalTrials.gov NCT01221467 NCT01440140 NCT01666028.

Publication types

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

MeSH terms

  • Adolescent
  • Adult
  • Blood Glucose / analysis*
  • Blood Glucose Self-Monitoring / instrumentation
  • Blood Glucose Self-Monitoring / standards*
  • Child
  • Cross-Over Studies
  • Diabetes Mellitus, Type 1 / blood*
  • Diabetes Mellitus, Type 1 / complications
  • Diabetes Mellitus, Type 1 / drug therapy
  • Equipment Design
  • Female
  • Glycated Hemoglobin A / analysis
  • Humans
  • Hypoglycemia / diagnosis
  • Hypoglycemia / drug therapy
  • Hypoglycemia / etiology
  • Hypoglycemic Agents / administration & dosage
  • Insulin / administration & dosage
  • Insulin Infusion Systems / standards
  • Male
  • Middle Aged
  • Reference Values
  • Reproducibility of Results
  • Social Conditions
  • Teach-Back Communication
  • Time Factors

Substances

  • Blood Glucose
  • Glycated Hemoglobin A
  • Hypoglycemic Agents
  • Insulin
  • hemoglobin A1c protein, human

Associated data

  • ClinicalTrials.gov/NCT01221467
  • ClinicalTrials.gov/NCT01440140
  • ClinicalTrials.gov/NCT01666028