Relationships of glucose concentrations in capillary whole blood, venous whole blood and venous plasma.

We studied the difference in glucose levels between capillary and venous whole blood during 75-g oral glucose tolerance test (OGTT) in 75 healthy subjects. Capillary and venous whole blood glucose values were measured by HK-G6PD method after deproteinization. The post-loaded glucose levels in capillary blood were significantly higher than those in venous blood, and the mean values of capillary and venous difference at 30, 60, 90, 120 and 180 min were 1.37, 1.40, 1.07, 0.95 and 0.52 mmol/l, respectively, with the maximum difference at 60 min. No correlation was found in the magnitude of the differences in glucose between capillary and venous blood specimens. We determined the inaccuracy of six self-monitoring blood glucose devices relative to the reference method using venous plasma, venous whole blood and capillary whole blood from 31 diabetic patients. The differences of mean values of venous whole blood and capillary whole blood, and venous whole blood and venous plasma, and capillary whole blood and venous plasma were 9.6%, 11.3% and -3.2%, respectively. The range of bias and Sy/x were 0.31-1.06 mmol/l and 0.71-1.07 mmol/l, respectively, compared to the reference method using venous plasma.