Discrepancies Between Capillary Glucose Measurements and Traditional Laboratory Assessments in Both Shock and Non-shock States After Trauma

Introduction: The purpose of this study was to analyze the accuracy of capillary blood glucose (CBG) against laboratory blood glucose (LBG) in critically ill trauma patients during the shock state.

Methods: All critically ill trauma patients admitted to the Surgical Intensive Care Unit at the Los Angeles County + University of Southern California Medical Center requiring blood glucose monitoring from January 2007 to December 2008 were included. Accuracy of CBG was compared against LBG during shock and non-shock states. Shock was defined as either systolic blood pressure <90 mm Hg or mean arterial pressure <70 mm Hg and the need for vasopressor therapy. The Bland-Altman method was used to determine the agreement between CBG and LBG during shock and non-shock states. CBG values were considered to disagree significantly with LBG values when the difference exceeded 15%.

Results: During the 2-y study period, a total of 1215 patients were admitted to the Surgical Intensive Care Unit. Overall, the mean age was 38.4 ± 20.9 y, 79.6% (967) were male, and 75.0% (911) sustained blunt trauma. A total of 1935 paired samples of CBG and LBG were included in this analysis (367 during shock and 1568 during non-shock). During shock, the mean difference between CBG and LBG levels was 13.4 mg/dL (95% CI, -15.4 to 42.2 mg/dL), and the limits of agreement were -27.1 and 53.9 mg/dL. A total of 136 CBG values (37.1%) differed from the LBG values by more than 15%. During non-shock, the mean difference between CBG and LBG levels was 12.6 mg/dL (95% CI, -19.9 to 32.5 mg/dL), and the limits of agreement were -20.6 and 45.8 mg/dL. A total of 639 CGB values (40.8%) differed from the LBG values by more than 15%. Agreement was lowest among hypoglycemic readings in both shock and non-shock states.

Conclusion: There is poor correlation between the capillary and laboratory glucose values in both shock and non-shock states.