title: Accuracy of subcutaneous continuous glucose monitoring in critically ill adults: improved sensor performance with enhanced calibrations.
abstract: OBJECTIVE
  Accurate real-time continuous glucose measurements may improve glucose control in the critical care unit. We evaluated the accuracy of the FreeStyle(®) Navigator(®) (Abbott Diabetes Care, Alameda, CA) subcutaneous continuous glucose monitoring (CGM) device in critically ill adults using two methods of calibration.
  
  
  METHODS
  In a randomized trial, paired CGM and reference glucose (hourly arterial blood glucose [ABG]) were collected over a 48-h period from 24 adults with critical illness (mean±SD age, 60±14 years; mean±SD body mass index, 29.6±9.3 kg/m(2); mean±SD Acute Physiology and Chronic Health Evaluation score, 12±4 [range, 6-19]) and hyperglycemia. In 12 subjects, the CGM device was calibrated at variable intervals of 1-6 h using ABG. In the other 12 subjects, the sensor was calibrated according to the manufacturer's instructions (1, 2, 10, and 24 h) using arterial blood and the built-in point-of-care glucometer.
  
  
  RESULTS
  In total, 1,060 CGM-ABG pairs were analyzed over the glucose range from 4.3 to 18.8 mmol/L. Using enhanced calibration median (interquartile range) every 169 (122-213) min, the absolute relative deviation was lower (7.0% [3.5, 13.0] vs. 12.8% [6.3, 21.8], P<0.001), and the percentage of points in the Clarke error grid Zone A was higher (87.8% vs. 70.2%).
  
  
  CONCLUSIONS
  Accuracy of the Navigator CGM device during critical illness was comparable to that observed in non-critical care settings. Further significant improvements in accuracy may be obtained by frequent calibrations with ABG measurements.
authors.affiliation: 1 Metabolic Research Laboratories, Institute of Metabolic Science, University of Cambridge , Cambridge, United Kingdom .
authors.forename: Lalantha
authors.initials: L
authors.lastname: Leelarathna
authors.forename: Shane W
authors.initials: SW
authors.lastname: English
authors.forename: Hood
authors.initials: H
authors.lastname: Thabit
authors.forename: Karen
authors.initials: K
authors.lastname: Caldwell
authors.forename: Janet M
authors.initials: JM
authors.lastname: Allen
authors.forename: Kavita
authors.initials: K
authors.lastname: Kumareswaran
authors.forename: Malgorzata E
authors.initials: ME
authors.lastname: Wilinska
authors.forename: Marianna
authors.initials: M
authors.lastname: Nodale
authors.forename: Ahmad
authors.initials: A
authors.lastname: Haidar
authors.forename: Mark L
authors.initials: ML
authors.lastname: Evans
authors.forename: Rowan
authors.initials: R
authors.lastname: Burnstein
authors.forename: Roman
authors.initials: R
authors.lastname: Hovorka
mesh_terms: D015374:Biosensing Techniques; D001786:Blood Glucose / Q000032:analysis* / Q000378:metabolism; D002138:Calibration; D016638:Critical Illness / Q000628:therapy; D005260:Female; D006442:Glycated Hemoglobin / Q000032:analysis* / Q000378:metabolism; D006801:Humans; D006943:Hyperglycemia / Q000378:metabolism*; D007362:Intensive Care Units; D008297:Male; D008991:Monitoring, Physiologic / Q000379:methods; D011237:Predictive Value of Tests; D011446:Prospective Studies; D015203:Reproducibility of Results
chemical_list: D001786:Blood Glucose; D006442:Glycated Hemoglobin; C517652:hemoglobin A1c protein, human