Abstract
The amount of trapped plasma, expressed as a percentage of the packed cell volume, was determined in samples of heparinized blood from 26 children with severe thalassaemia and from 37 normal children over a wide range of artificial packed cell volumes. There was invariably more plasma trapped among the centrifuged red cells of the thalassaemic children, the mean difference between normal and thalassaemic children being 1% of the packed cell volume. In both normal and thalassaemic children the volume of trapped plasma, expressed as a percentage of the packed cell volume, was directly proportional to the packed cell volume. Plasma trapping did not appear to be related to the size of the erythrocytes in either the normal or the thalassaemic children. It varied inversely with the density of the red cells, as estimated by their mean haemoglobin concentration, in the thalassaemic children.