Validation and feasibility of two Continuous Glucose Monitoring

Purpose: To validate two Continuous Glucose Monitoring systems (CGMs) against arterial AccuChek® point-of-care glucose measurements in critically ill patients. Methods: Two CGMs, Guardian RT® (GRT) and Freestyle Navigator® (FsN), were used for 5 days in mechanically ventilated patients with Multiple Organ Dysfunction syndrome. The measurements at T=0, T +10 min and T + 20 min were linked to T=0 reference data to investigate a possible sensor delay. Data were analyzed by: 1) the absolute difference, 2) correlation, 3) Bland-Altman analysis, 4) Clarke Error Grid analysis. The practical features and effect of vaso-active medication on CGMs accuracy were evaluated. Results: In 350 paired measurements in 18 patients, the Median Absolute Difference was 10.6% to 11.6% for FsN® and 10.3% to 11.5% for GRT®. Pearson’s correlation coefficients were 0.79 to 0.82 for FsN® and 0.76 to 0.80 for GRT®. Limits of agreement for Bland Altman analysis varied between -2.49 to 1.99 for FsN® and between -2.59 to 2.67 for GRT®. Of the FsN® measurements, 96.9% – 97.2% were in zones A+B of the Clarke Error Grid, versus 97.6% – 97.8% for GRT®. Both CGMs performed slightly better at T +20 min compared to T=0 measurements. seven hypoglycaemic events were detected by both CGMs systems and not by routine AccuChek® measurement. The GRT® system had fewer practical problems compared to the FsN® system. No influence of vasoactive drugs was found. Conclusions: Both systems performed equally well. Using a CGMs can show early detection of hypoglycaemia. A disadvantage of the FsN® is the 10-hour warm-up period it requires.