Comparison of blood counts in venous, fingertip and arterial blood and their measurement variation

We compared routine blood pictures in venous, fingertip and arterial blood and their measurement variation. A pair of venous and fingertip blood sampl es were simultaneously collected from 24 volunteers, and another pair of ve nous and arterial samples from another 12 volunteers. The volunteers were h ealthy adults, aged 20-22 years, with males and females in equal numbers. T hree aliquots of blood were taken from each person for three measurements o f blood counts, including haemoglobin concentration and haemocrit, using an automatic haematology analyser, Compared to arterial blood, there was a si gnificant increase of erythrocyte count (2.7%) and haematocrit (3.1%) in th e venous blood. The total and large leucocyte counts were significantly hig her (9.2% and 12.6%, respectively) in the fingertip blood than in the venou s blood. There were a decreasing number of leucocytes in the fingertip bloo d with repeated sampling. The intermeasurement variation for total leucocyt e or haemoglobin measurement was significantly larger as measured with the fingertip blood or arterial blood than with the venous blood. The intermeas urement coefficients of variation of haemoglobin (1.3%) and small leucocyte ratio or platelet (approximately 4.0%) measurements with venous and arteri al blood were the smallest and largest, respectively. Volume of arterial pl asma was diminished by 2-3% after microcirculation. Elevation of total leuc ocyte count in the fingertip blood was mainly due to the increase of granul ocytes. Measurement with venous blood was of better precision than with fin gertip or arterial blood.