Stabilization of Glucose in Blood Samples: Why It Matters

Abstract

In this issue of Clinical Chemistry , Gambino et al. (1) describe careful studies of a blood-collection container that stabilizes the concentration of glucose in blood samples. At a time of an increasing disease burden attributable to diabetes and the use of lower glucose concentrations than in the past for the diagnosis of diabetes, this study and its findings are especially important. Measurements of glucose are used worldwide to diagnose diabetes and to identify patients at risk of developing diabetes [e.g., (2)(3)]. For both diagnosis and risk assessment, fixed cutpoints of plasma glucose concentrations are used to classify patients and to make decisions regarding management. For this reason, all steps in the analytical process require careful attention. Clinical chemists in hospital laboratories and diagnostic companies have made great strides in improving the measurement of glucose. With the use of enzymatic methods and sophisticated analyzers with stable optics, electronics, fluid handling, and other components, central clinical laboratories routinely achieve an astoundingly low within-laboratory imprecision (CV) of 1%–2%. [Glucose meters do not fare so well and are not recommended for diagnosis of diabetes (4).] By contrast, the preanalytical issues surrounding glucose measurements have not been solved. The loss of glucose in blood samples has been studied for many years (5). Glucose is lost through glycolysis at a rate of 5%–7%/h at concentrations near the reference interval. In absolute terms, a loss in glucose of about 0.67 mmol/L (12 mg/dL) occurs at a concentration of 5.55 mmol/L (100 mg/dL) after 2 h at room temperature (6). Higher rates of loss occur commonly, such as with increased ambient temperature and in samples with high white blood cell counts. In 1923, Major introduced potassium fluoride as a potent inhibitor of glycolysis (7), and fluoride, usually as NaF, has been used for decades to …