Real-Time Continuous Glucose Monitoring Shows High Accuracy within 6 Hours after Sensor Calibration: A Prospective Study

Xiao-Yan Yue,Ye-Hua Cai,Jian-Xin Zhou,Ning-Ning Yin,Yi Zheng,Richard C Willson

doi:10.1371/journal.pone.0060070

Abstract

Accurate and timely glucose monitoring is essential in intensive care units. Real-time continuous glucose monitoring system (CGMS) has been advocated for many years to improve glycemic management in critically ill patients. In order to determine the effect of calibration time on the accuracy of CGMS, real-time subcutaneous CGMS was used in 18 critically ill patients. CGMS sensor was calibrated with blood glucose measurements by blood gas/glucose analyzer every 12 hours. Venous blood was sampled every 2 to 4 hours, and glucose concentration was measured by standard central laboratory device (CLD) and by blood gas/glucose analyzer. With CLD measurement as reference, relative absolute difference (mean±SD) in CGMS and blood gas/glucose analyzer were 14.4%±12.2% and 6.5%±6.2%, respectively. The percentage of matched points in Clarke error grid zone A was 74.8% in CGMS, and 98.4% in blood gas/glucose analyzer. The relative absolute difference of CGMS obtained within 6 hours after sensor calibration (8.8%±7.2%) was significantly less than that between 6 to 12 hours after calibration (20.1%±13.5%, p<0.0001). The percentage of matched points in Clarke error grid zone A was also significantly higher in data sets within 6 hours after calibration (92.4% versus 57.1%, p<0.0001). In conclusion, real-time subcutaneous CGMS is accurate in glucose monitoring in critically ill patients. CGMS sensor should be calibrated less than 6 hours, no matter what time interval recommended by manufacturer.

Highlights

Epidemiologic data have shown that there is a high incidence of hyperglycemia in critically ill patients, and its occurrence is associated with adverse clinical outcome [1,2]
The appropriate target range of blood glucose in critically ill patients is inconclusive at present time, it has been widely accepted that accurate and timely measurement of blood glucose is essential in intensive care unit (ICU) setting, even in patients receiving a conventional glucose control protocol [6,7]
It has been found that glucose measurements by blood gas/glucose analyzers located in ICU are more accurate than those by handheld glucose analyzers [11,12]

Summary

Introduction

Epidemiologic data have shown that there is a high incidence of hyperglycemia in critically ill patients, and its occurrence is associated with adverse clinical outcome [1,2]. Handheld glucose analyzer can provide a fast bedside result, its accuracy in critically ill patients has been questioned [9,10] Another type of POC instrument commonly used in glucose monitoring in ICU is blood gas analyzer with function of glucose measurement [3]. The limitation of glucose monitoring method in critical care settings may contribute to the discrepancy of results in glucose control studies, which may hamper the further investigation [13]. These issues have urged the need for real-time continuous glucose monitoring system (CGMS) devices [6]

Objectives

Methods

Results

Conclusion