Experimental basis of standardized specimen collection: Effect of posture on blood picture

22 subjectively healthy females were supine, sat in an armchair and stood while specimens of peripheral venous blood were collected after at least 15 min in each position without using a tourniquet. The albumin, haemoglobin, erythrocyte concentration and the haematocrit increased significantly when the subjects assumed a more erect position, probably as a result of increased hydrostatic pressure. The leucocyte count did not rise, and there was a statistically significant drop in the lymphocyte concentration when changing from supine to sitting. However, the leucocyte concentration rose significantly when the subjects stood up from supine or sitting, and the platelets increased significantly from supine to sitting or standing. When interpreting laboratory data, the difference in the behaviour of different cell species should be kept in mind. However, on the whole this study supports the stipulation contained in international recommendations that the posture of the subject should be standardized before collection of peripheral blood for haematological tests.