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Previous methods for assessing the control of diabetes at home have concentrated on the measurement of glucose concentrations in urine and, more recently, blood. These levels reflect only one aspect of deranged metabolism in the disease. A technique is described whereby glucose, lactate, and 3-hydroxybutyrate can be measured in capillary blood samples dried on boric acid impregnated filter paper. The technique is sufficiently sensitive to measure 0.05 mmol/l glucose, 0.02 mmol/l lactate, and 0.004 mmol/1 3-hydroxybutyrate with precisions of 4.0%, 4.5%, and 8.0%, respectively. This method could prove useful in the broader metabolic assessment of the diabetic state.

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.