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 Ò Navigator Ò (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.

Factory-Calibrated Continuous Glucose Sensors: The Science Behind the Technology

“…To our knowledge, no scientific studies have been published previously evaluating the feasibility of factory calibration besides the ones leading to FreeStyle Libre. [9][10][11][12][13] All calibration-related studies and publications were focused on understanding and improving the standard BG-based fingerstick calibration [14][15][16][17][18][19][20][21][22][23][24][25][26][27][28][29][30] or overcoming transient effects, such as lag and signal artifacts [31][32][33][34][35] that can impact calibration. This demonstrates the novelty of this alternative approach and also possibly the superiority of the chemistry used in FreeStyle Libre over other sensor systems.…”

Accuracy of Intra-arterial and Subcutaneous Continuous Glucose Monitoring in Postoperative Cardiac Surgery Patients in the ICU

“…Improvements in accuracy of the FreeStyle Navigator device may be obtained by performing calibrations more frequently. 14 Another open-label study investigated the use of the GluCath IA-CGM device in cardiac surgery patients admitted to the ICU and reported similar accuracy with an aggregate MARD of 13.0% (individual sensors ranging from 4.7% to 33.5%). 15 As in all studies in this field, the extent of acceptable deviation between sensor and arterial reference glucose measurements can be debated.…”

Inpatient Continuous Glucose Monitoring and Glycemic Outcomes

“…This review excluded studies evaluating CGM accuracy and reliability, which have been reviewed previously. [23][24][25][26][27][28][29][30][31] While we reference isolated inpatient non-ICU CGM cases, we primarily included observational and randomized CGM glycemic outcome studies in this review (six ICU studies, three non-ICU studies), reflecting the scarcity of evidence on this topic, and the need for further studies.…”

“…As of 2011, the Endocrine Society recommended against inpatient CGM due to lack of published safety and efficacy data. 22 Since that time, numerous publications have evaluated inpatient CGM accuracy, reliability, and safety; [23][24][25][26][27][28][29][30][31] however, few studies have evaluated the glycemic outcomes of subcutaneous CGM, which are limited by the lack of Type 1 Diabetes Mellitus (T1DM) subjects and the use of different CGM systems. This article will review subcutaneous CGM glycemic outcomes in the adult ICU and non-ICU setting.…”