Accuracy of subcutaneous continuous glucose monitoring in critically ill adults: improved sensor performance with enhanced calibrations

Diabetes Technol Ther. 2014 Feb;16(2):97-101. doi: 10.1089/dia.2013.0221. Epub 2013 Nov 4.


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.

Subjects and 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.

Publication types

  • Randomized Controlled Trial
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Biosensing Techniques
  • Blood Glucose / analysis*
  • Blood Glucose / metabolism
  • Calibration
  • Critical Illness* / therapy
  • Female
  • Glycated Hemoglobin A / analysis*
  • Glycated Hemoglobin A / metabolism
  • Humans
  • Hyperglycemia / metabolism*
  • Intensive Care Units
  • Male
  • Monitoring, Physiologic* / methods
  • Predictive Value of Tests
  • Prospective Studies
  • Reproducibility of Results


  • Blood Glucose
  • Glycated Hemoglobin A
  • hemoglobin A1c protein, human