Comparison Of Capillary Blood Glucose Versus Arterial Blood Glucose In Diabetic Patients Admitted In Icu On Vasopressor Support – A One Year Cross Sectional Observational Study

Abstract

Background: Glycemic control in critically ill patients decreases infection and mortality. Patients receiving vasopressors have altered peripheral perfusion, which may affect accuracy of capillary blood glucose values measured with point of care device. Objective: Comparison of capillary blood glucose versus arterial blood glucose in diabetic patients admitted in ICU on vasopressor support. Methods: The accuracy of capillary and arterial blood glucose meter measurements was compared with central laboratory arterial glucose measurements; the factors associated with inaccurate measures were also determined. The accuracy of arterial and capillary samples v/s standard lab method were evaluated according to the intra class correlation coefficient, on the basis of International Organization for Standardization (ISO 15197:2013 standards). Surveillance Error Grid (SEG) analysis and Clarke’s error grid was used for analysis. Agreement between the two samples was determined using the method of Bland and Altman. RESULTS: The level of agreement of both capillary blood glucose and arterial blood glucose measured by the glucometer with respect to standard laboratory method according to the ISO 15197 guideline 2013 was only 80.0% and 81.6% respectively. Bland–Altman plot showed a mean bias of -1.44 mg/dL in capillary POCT method whereas in arterial POCT method, mean bias was 2.37 mg/dL. Distribution of the results in Surveillance Error Grid analysis shows that, capillary blood glucose values had (10.4%) data pairs outside no risk zone while arterial blood glucose group had only 5.6% data pairs outside no risk zone. But none of the values were outside of the slight lower risk zone (light green). As per Clarke’s error grid analysis, 84% of the capillary POCT and 90.4% of arterial POCT values with respect to standard lab values were within Zone A and all other remaining values were within zone B indicating that none of the values led to erroneous treatment clinically. CONCLUSION: • Arterial point of care testing values had slightly better agreement in comparison to capillary point of care testing which could be deemed negligible. • Both the values were inaccurate according to ISO standards although they had reasonably good correlation with standard lab values. • Most studies conducted so far have shown and recommended arterial blood glucose estimation at the bedside over capillary point of care testing among critically ill patients. As per our study we choose to conclude that there is no significant variation between arterial and capillary point of care testing for blood glucose estimation. Considering arterial as a more invasive method, capillary method of glucose estimation stands as a reasonable and easy option for bedside glucose monitoring among critically ill patients on vasopressor support.