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.