Measurement of erythrocyte filterability using washed-erythrocyte and whole-blood methods

A positive-pressure, washed-erythrocyte method for the measurement of red cell filterability has been compared with a negative-pressure, whole-blood technique. Using 5 µm pore-size polycarbonate filters, both methods detected a sub-population of 4–5 × 10⁷/l glutaraldehyde-hardened erythrocytes and both showed a decrease in erythrocyte filterability in proportion to increasing concentrations of added fibrinogen. The washed-erythrocyte method gave better reproducibility with less variation between filter batches and is recommended for the study of patients in whom plasma hyperproteinaemia may adversely affect erythrocyte filtration.