Comparability of Blood Glucose Concentrations Measured in Different Sample Systems for Detecting Glucose Intolerance (Technical Briefs‪)‬

Glucose concentrations are usually measured in whole blood or plasma. Plasma values are influenced by the concentration of proteins, especially those with large volumes, such as lipoproteins. Blood values additionally depend on the total volume of the various blood cells, which is usually expressed as the hematocrit (1,2). The interconversion of glucose values for venous and capillary blood is further complicated by the arteriovenous difference. In the fasting state, the glucose concentrations in arterial, capillary, and (forearm) venous blood are supposed to be almost indistinguishable. In contrast, arterial blood glucose values may differ by 20% or as much as 70% in the postprandial state (3,4). The mean arteriovenous differences are largest in lean nondiabetic individuals, smallest in diabetic individuals, and larger in deep veins than in superficial vessels (1,5). Other factors can influence the differences in glucose concentrations among the various samples (6-9). Thus, the conversion of concentration values from one system (or sample type) to another is subject to unpredictable errors.