A comparison between haematological parameters in 'capillary' and venous blood from healthy adults

In 40 healthy adult volunteers of both sexes blood samples were taken simultaneously from an antecubital vein in EDTA-Vacutainers and from a fingertip in EDTA-Microtainers. Haematological measurements were subsequently performed in an Ortho-ELT 800 WS analyzer. Significant differences were obtained between the two sets of samples. In accordance with current literature, the 'capillary' thrombocyte count was either identical to, or more frequently substantially lower than the corresponding venous count. On the contrary, the 'capillary' erythrocyte count and the haematocrit and haemoglobin values significantly exceeded those of venous blood, while the red cell indices MCV, MCH and MCHC were identical. The total leucocyte count was substantially elevated in 'capillary' blood compared with the corresponding venous samples. Moreover, the 'capillary' differential leucocyte counts showed elevations which directly reflected the various particles' size. Possible explanations of these findings are discussed.