Performance of three enzymic methods for filter paper glucose determination.

Collection of blood spots on filter paper offers a practical alternative for home monitoring of diabetic patients. We have compared the merits of three protein precipitants, trichloracetic acid (TCA), perchloric acid (PCA) and sulphosalicylic acid (SSA) for the elution of glucose from the filter paper, and their subsequent effects on three enzymic methods, glucose dehydrogenase (GDH), hexokinase (HK), and glucose oxidase (GOD) for the determination of glucose using a microcentrifugal analyser. The combination of TCA elutant with the GDH method was superior with respect to time course of reaction and elution time from the filter paper, and was chosen for routine use. Within- and between-batch precision for this method was 2.7% and 3.2% respectively at normal glucose concentrations. Recovery of glucose added to whole blood was 110 +/- 5%. Comparison with an automated glucose oxidase method for plasma glucose gave a slope of 1.1, intercept of -0.7 and a correlation coefficient of 0.9 (n = 64). We conclude that the combination of TCA and glucose dehydrogenase provides a robust, precise and accurate method for the quantitation of glucose in filter-paper blood spots. The procedure offers increased sensitivity and better precision than GOD methods. The use of TCA as elutant gives a faster elution time and has the least effect on any of the enzymic methods.