229-OR: A Calibration Protocol for Continuous Glucose Monitor Accuracy in the ICU

Abstract

Guidelines now recommend inpatient continuous glucose monitor (CGM) use, assuming that it is sufficiently accurate due to its apparent safety. The FDA issued a non-objection letter for inpatient CGM use, but it is not yet officially approved for hospitals, including in the ICU. To further study CGM in the ICU, we tested the accuracy of the Dexcom G6 (G6) in 32 adults in a medical-surgical ICU in Vancouver, BC using a calibration protocol in 1035 matched CGM and arterial point-of-care (POC) pairs. Our first uncalibrated study had a mean absolute relative differential (MARD) of 13.24%, which barely meets the critical care expert recommendation of MARD <14%. This study aims to show a higher accuracy can be achieved with a simple calibration protocol on Day 1, then none thereafter. The MARD for calibrated patients was 9.27%, significantly lower than 13.19% for uncalibrated patients (p<0.001). Calibration also had excellent safety with 100% of values within Clarke Error Grid Zones A and B compared to 99.07% without calibration. Our protocol achieved the lowest MARD and safest Clarke Error Grid profile of any ICU study comparing CGM to standard of care arterial POC and well exceeds the critical care expert recommendations. Our large sample of heterogenous critically ill patients also reached comparable accuracy to the MARD of 9% for G6 in outpatients. We believe our calibration protocol will allow CGM to be used with sufficient accuracy in the ICU. Disclosure S.Bann: None. J.C.Hercus: None. P.Atkins: None. A.Alkhairy: None. D.M.Thompson: None.