The influence of a soiled finger in capillary blood glucose monitoring.

There are several aspects concerning self-monitoring of blood glucose (SMBG) which can influence the outcome of the measurement. For example, there is no general agreement regarding the use of the first or second drop of blood for glucose monitoring. Our aim was to investigate the influence of wiping a drop of blood on glucose concentrations measured by SMBG when having a finger soiled with different sugar-containing products, and the effects of cleaning a soiled finger with chlorhexidine. Twenty-five non-diabetic adults participated. After they had washed their hands, their fingers were soiled with various sugar-containing products. The products used were dextrose, fruit, jam, honey, and chocolate paste. Glucose concentrations were determined in the first, second and third drop of capillary blood (intervention 1). Furthermore, measurements were done in one drop before and in two drops of blood after cleaning a soiled finger with chlorhexidine (intervention 2). All results were compared with a control measurement from a clean and dry finger. Glucose levels were determined with the Accu-Check Inform II (Roche, Almere, the Netherlands). The general linear model (GLM) with repeated measures (multivariate testing) was used to test for overall changes in glucose concentrations. Furthermore, using the ‘simple’ contrast, each concentration was compared with the control. Table 1 shows glucose concentrations in sequential drops of blood in different circumstances. In both interventions the highest glucose concentrations were found in the first drop of blood, with a significant decrease in sequential blood glucose concentrations from the first drop of blood to control (p=0.013 and p<0.0005 respectively). In 53% of the cases in intervention 1 and in 34% of the cases in intervention 2, the blood glucose concentration in the third drop of blood was still more than 10% higher than the control measurement. In the literature only one study describes the difference between glucose concentrations in the first and the second drop of blood. This study showed no differences between the readings. The study was conducted in volunteers l e t t e r t o t h e e d i t or