Point-of-Care versus Central Laboratory Glucose Testing in Postoperative Cardiac Surgery Patients

Objective. To determine the accuracy of the glucometer currently used for point-of-care testing (POCT) of blood glucose in our cardiothoracic surgery intensive care unit (CTICU). Design. Prospective cohort study. Setting. Tertiary care community hospital affiliated with a school of medicine. Participants. Coronary artery bypass graft (CABG) surgery patients. Measurements. Blood glucose levels obtained via POCT with a glucometer using fingerstick and radial artery blood samples were compared with values obtained via central laboratory testing of radial artery blood samples (gold standard) in 106 CABG patients on continuous insulin infusions (CII) upon arrival to the CTICU from the operating room and 102 CABG patients on CII in the CTICU 6 hours later. Results. Fingerstick POCT and central lab blood glucose values correlated well (r = 0.83 for admission and 0.86 for 6-hour values), but the mean values were significantly different as determined by paired t-tests. Upon arrival, the fingerstick POCT mean value was 120.9 mg/dL, while the central laboratory value was 127.9 mg/dL (P value = 0.03). At the 6-hour time point, the mean value for fingerstick POCT was 129.7 mg/dL compared to a central laboratory value of 137.3 (P value = 0.02). Conclusion. The blood glucose POCT values correlated well with central laboratory values, but the values were statistically significantly different. Nevertheless, accurate clinical decisions were made despite the inaccuracies of POCT glucose testing, as experienced bedside nurses were able to use the glucometer successfully and safely. The device’s results informed them when the blood glucose was out of a prescibed range and the direction of the change, and they were able to adjust the CII accordingly.