title: Accuracy of Continuous Glucose Monitoring During Three Closed-Loop Home Studies Under Free-Living Conditions.
abstract: OBJECTIVE
  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.
  
  
  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.
authors.affiliation: 1 Wellcome Trust-MRC Institute of Metabolic Science, University of Cambridge , Cambridge, United Kingdom .
authors.forename: Hood
authors.initials: H
authors.lastname: Thabit
authors.affiliation: 1 Wellcome Trust-MRC Institute of Metabolic Science, University of Cambridge , Cambridge, United Kingdom .
authors.forename: Lalantha
authors.initials: L
authors.lastname: Leelarathna
authors.affiliation: 1 Wellcome Trust-MRC Institute of Metabolic Science, University of Cambridge , Cambridge, United Kingdom .
authors.forename: Malgorzata E
authors.initials: ME
authors.lastname: Wilinska
authors.affiliation: 1 Wellcome Trust-MRC Institute of Metabolic Science, University of Cambridge , Cambridge, United Kingdom .
authors.forename: Daniella
authors.initials: D
authors.lastname: Elleri
authors.affiliation: 1 Wellcome Trust-MRC Institute of Metabolic Science, University of Cambridge , Cambridge, United Kingdom .
authors.forename: Janet M
authors.initials: JM
authors.lastname: Allen
authors.affiliation: 2 Academic Unit of Diabetes, Endocrinology and Metabolism, Department of Human Metabolism, University of Sheffield , Sheffield, United Kingdom .
authors.forename: Alexandra
authors.initials: A
authors.lastname: Lubina-Solomon
authors.affiliation: 2 Academic Unit of Diabetes, Endocrinology and Metabolism, Department of Human Metabolism, University of Sheffield , Sheffield, United Kingdom .
authors.forename: Emma
authors.initials: E
authors.lastname: Walkinshaw
authors.affiliation: 3 Diabetes Research Group, King's College London , London, United Kingdom .
authors.forename: Marietta
authors.initials: M
authors.lastname: Stadler
authors.affiliation: 3 Diabetes Research Group, King's College London , London, United Kingdom .
authors.forename: Pratik
authors.initials: P
authors.lastname: Choudhary
authors.affiliation: 4 Division of Endocrinology and Metabolism, Department of Internal Medicine, Medical University of Graz , Graz, Austria .
authors.forename: Julia K
authors.initials: JK
authors.lastname: Mader
authors.affiliation: 5 Profil , Neuss, Germany .
authors.forename: Sibylle
authors.initials: S
authors.lastname: Dellweg
authors.affiliation: 5 Profil , Neuss, Germany .
authors.forename: Carsten
authors.initials: C
authors.lastname: Benesch
authors.affiliation: 4 Division of Endocrinology and Metabolism, Department of Internal Medicine, Medical University of Graz , Graz, Austria .
authors.forename: Thomas R
authors.initials: TR
authors.lastname: Pieber
authors.affiliation: 5 Profil , Neuss, Germany .
authors.forename: Sabine
authors.initials: S
authors.lastname: Arnolds
authors.affiliation: 2 Academic Unit of Diabetes, Endocrinology and Metabolism, Department of Human Metabolism, University of Sheffield , Sheffield, United Kingdom .
authors.forename: Simon R
authors.initials: SR
authors.lastname: Heller
authors.affiliation: 3 Diabetes Research Group, King's College London , London, United Kingdom .
authors.forename: Stephanie A
authors.initials: SA
authors.lastname: Amiel
authors.affiliation: 1 Wellcome Trust-MRC Institute of Metabolic Science, University of Cambridge , Cambridge, United Kingdom .
authors.forename: David
authors.initials: D
authors.lastname: Dunger
authors.affiliation: 1 Wellcome Trust-MRC Institute of Metabolic Science, University of Cambridge , Cambridge, United Kingdom .
authors.forename: Mark L
authors.initials: ML
authors.lastname: Evans
authors.affiliation: 1 Wellcome Trust-MRC Institute of Metabolic Science, University of Cambridge , Cambridge, United Kingdom .
authors.forename: Roman
authors.initials: R
authors.lastname: Hovorka
mesh_terms: D000293:Adolescent; D000328:Adult; D001786:Blood Glucose / Q000032:analysis*; D015190:Blood Glucose Self-Monitoring / Q000295:instrumentation / Q000592:standards*; D002648:Child; D018592:Cross-Over Studies; D003922:Diabetes Mellitus, Type 1 / Q000097:blood* / Q000150:complications / Q000188:drug therapy; D004867:Equipment Design; D005260:Female; D006442:Glycated Hemoglobin / Q000032:analysis; D006801:Humans; D007003:Hypoglycemia / Q000175:diagnosis / Q000188:drug therapy / Q000209:etiology; D007004:Hypoglycemic Agents / Q000008:administration & dosage; D007328:Insulin / Q000008:administration & dosage; D007332:Insulin Infusion Systems / Q000592:standards; D008297:Male; D008875:Middle Aged; D012016:Reference Values; D015203:Reproducibility of Results; D012924:Social Conditions; D064871:Teach-Back Communication; D013997:Time Factors
chemical_list: D001786:Blood Glucose; D006442:Glycated Hemoglobin; D007004:Hypoglycemic Agents; D007328:Insulin; C517652:hemoglobin A1c protein, human