Accuracy of Plasma Glucose Measurements in the Hypoglycemic Range

OBJECTIVE: This study was designed to evaluate three different enzymatic methods for glucose measurement in plasma samples with special emphasis on glucose concentrations in the hypoglycemic range. RESEARCH DESIGN AND METHODS: Glucose dehydrogenase (Hemo-Cue analyzer), glucose oxidase (YSI analyzer), and hexokinase (Abbott analyzer) methods were used to measure plasma samples that were obtained during research studies. RESULTS: Mean glucose concentrations (n = 240) were 5.3 +/- 0.2, 5.4 +/- 0.2, and 5.6 +/- 0.2 mM (95.6 +/- 3.9, 96.7 +/- 3.9, and 101.6 +/- 4.0 mg/dl) using glucose dehydrogenase, glucose oxidase, and hexokinase, respectively (NS). In the hypoglycemic range, mean glucose concentrations with each method retained the same hierarchy of measurements: 2.7 +/- 0.05, 2.8 +/- 0.04, and 2.9 +/- 0.03 mM (48.4 +/- 0.9, 50.6 +/- 0.8, and 52.3 +/- 0.6 mg/dl) by glucose dehydrogenase, glucose oxidase, and hexokinase, respectively (P < 0.005). Individual glucose dehydrogenase measurements (n = 240) correlated well with glucose oxidase and hexokinase, r = 0.99, and were considerably easier to perform at the bedside. The differences between the glucose measurement methods were consistent and similar in low, normal, and high concentration ranges. CONCLUSIONS: We conclude that any interpretation or comparison of critical clinical and research measurements of glucose in different settings take into account methodological differences, particularly in the hypoglycemic range.