title: Comparison of the numerical and clinical accuracy of four continuous glucose monitors.
abstract: OBJECTIVE
  The purpose of this study was to compare the numerical and clinical accuracy of four continuous glucose monitors (CGMs): Guardian, DexCom, Navigator, and Glucoday.
  
  
  METHODS
  Accuracy data for the four CGMs were collected in two studies: Study 1 enrolled 14 adults with type 1 diabetes at the University of Virginia (UVA), Charlottesville, Virginia; study 2 enrolled 20 adults with type 1 diabetes at the Profil Institute for Metabolic Research, Neuss, Germany. All participants underwent hyperinsulinemic clamps including 1.5-2 h of maintained euglycemia at 5.6 mmol/l followed by descent into hypoglycemia, sustained hypoglycemia at 2.5 mmol/l for 30 min, and recovery. Reference blood glucose sampling was performed every 5 min. The UVA study tested Guardian, DexCom, and Navigator simultaneously; the Profil study tested Glucoday.
  
  
  RESULTS
  Regarding numerical accuracy, during euglycemia, the mean absolute relative differences (MARDs) of Guardian, DexCom, Navigator, and Glucoday were 15.2, 21.2, 15.3, and 15.6%, respectively. During hypoglycemia, the MARDs were 16.1, 21.5, 10.3, and 17.5%, respectively. Regarding clinical accuracy, continuous glucose-error grid analysis (CG-EGA) revealed 98.9, 98.3, 98.6, and 95.5% zones A + B hits in euglycemia. During hypoglycemia, zones A + B hits were 84.4, 97.0, and 96.2% for Guardian, Navigator, and Glucoday, respectively. Because of frequent loss of sensitivity, there were insufficient hypoglycemic DexCom data to perform CG-EGA.
  
  
  CONCLUSIONS
  The numerical accuracy of Guardian, Navigator, and Glucoday was comparable, with an advantage to the Navigator in hypoglycemia; the numerical errors of the DexCom were approximately 30% larger. The clinical accuracy of the four sensors was similar in euglycemia and was higher for the Navigator and Glucoday in hypoglycemia.
authors.affiliation: University of Virginia, Charlottesville, Virginia, USA. boris@virginia.edu
authors.forename: Boris
authors.initials: B
authors.lastname: Kovatchev
authors.forename: Stacey
authors.initials: S
authors.lastname: Anderson
authors.forename: Lutz
authors.initials: L
authors.lastname: Heinemann
authors.forename: William
authors.initials: W
authors.lastname: Clarke
mesh_terms: D000328:Adult; D001786:Blood Glucose / Q000032:analysis*; D003922:Diabetes Mellitus, Type 1 / Q000097:blood*; D004867:Equipment Design; D005858:Germany; D006801:Humans; D007003:Hypoglycemia / Q000097:blood; D008991:Monitoring, Physiologic / Q000295:instrumentation* / Q000592:standards; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D014768:Virginia
chemical_list: D001786:Blood Glucose