Experimental basis of standardized specimen collection: the effect of the site of venipuncture on the blood picture, the white blood cell differential count, and the serum albumin concentration

The effect of the specimen collection site on blood picture and WBC differential count was investigated in 13 and 25 volunteers, respectively. Lower values were found for the mature neutrophils and higher monocyte values in ear and finger blood compared to venous blood. There were no statistically significant differences in the WBC differential count values found in the ear and finger specimens. A higher S-Alb concentration was found in ear and finger specimens compared to venous blood. The average WBC concentration was higher in the ear and finger specimens than in the venous blood (7.66 x 10(9)/l, 7.11 x 10(9)/l and 6.88 x 10(9)/l, respectively). Also the platelet concentration exhibited a statistically significant difference, the mean concentrations being 273 x 10(9)/l, 260 x 10(9)/l and 231 x 10(9)/l in the vein, finger and ear specimens, respectively. The differences found are partly explained by peripheral ultrafiltration of intravascular fluid, leading to haemoconcentration, and partly by the different properties of different white blood cells. In conclusion, the specimens for blood picture and WBC differential count should always be obtained from the same site, especially in follow-up cases.