Evaluation of Leucocyte Removal Methods for Studies of Erythrocyte Deformability

Erythrocyte filtration, as measured by the initial-flow-rate Hemorheometre technique, showed a highly significant correlation (r = 0.603, P < 0.001) with even a small number of contaminating leucocytes (mean 0.08 × 10⁹/l, SEM 0.01) in 29 erythrocyte test suspensions. Failure to reduce leucocyte contamination to <0.025 × 10⁹/l caused falsely abnormal erythrocyte filtration values. Centrifugation failed to remove sufficient leucocytes from anaemic blood specimens but pre-filtration through Imugard IG500 cotton wool reduced leucocyte contamination to <0.025 × 10⁹/l in 73 of 74 blood samples. There was no evidence for selective cotton wool trapping of erythrocyte sub-populations to an extent that affected rheological measurements obtained by the Hemorheometre, the Ektacytometer, or by adhesion of erythrocytes to cultured human vascular endothelium.