Oxygen effects on glucose meter measurements with glucose dehydrogenase- and oxidase-based test strips for point-of-care testing

Objectives: To determine the effects of different oxygen tensions (Po-2) on glucose measurements with glucose dehydrogenase (GD)-based and glucose oxidase (GO)-based test strips, to quantitate changes in glucose measurements observed with different Po-2 levels, and to discuss the potential risks of oxygen-derived glucose errors in critical care. Design: Venous blood from healthy volunteers was tonometered to create different oxygen tensions simulating patient arterial Po-2 levels. Venous blood from diabetic patients was exposed to air to alter oxygen tensions simulating changes in Po-2 during sample handling. Whole-blood glucose measurements obtained from these samples with six glucose meters were compared with reference analyzer plasma glucose measurements. Glucose differences were plotted vs. different Po-2 levels to identify error trends. Error tolerances were as follows: a) within +/-15 mg/dL of the reference measurement for glucose levels less than or equal to 100 mg/dL; and b) within +/-15% of the reference measurement for glucose levels >100 mg/dL. Setting and Subjects: Five healthy volunteers in the bench study and 11 diabetic patients in the clinical study. Results: In the bench study, increases in Po-2 levels decreased glucose measured with GO-based amperometric test strips, mainly at Po-2 levels >100 torr. At nearly constant glucose concentrations, glucose meter systems showed large variations at low (39 torr) vs. high (396 torr) Po-2 levels. Glucose measured with GO-based amperometric and GO-based photometric test strips generally were within error tolerances. In the clinical study, 31.6% (Precision PCx), 20.2% (Precision QID), and 23.0% (Glucometer Elite) of glucose measurements with GO-based amperometric test strips, 14.3% (SureStep) of glucose measurements with GO-based photometric test strips, and 4.6% (Accu-Chek Advantage H) and 5.9% (Accu-Chek Comfort Curve) of glucose measurements with GO-based amperometric test strips were out of the error tolerances. Conclusions: Different oxygen tensions do not significantly affect glucose measured with the GO-based amperometric test strips, and have minimal effect on GO-based photometric test strips, Increases in oxygen tension lowered glucose measured with GO-based amperometric test strips. We recommend that the effects of different oxygen tensions in blood samples on glucose measurements be minimized by using oxygen-independent test strips for point-of-care glucose testing in critically ill and other patients with high or unpredictable blood Po-2 levels.