The fragility of normal and abnormal erythrocytes in a controlled hydrodynamic shear field.

Fresh human erythrocytes (suspended in a compatible isotonic viscous saline medium containing plasma) were disrupted by the uniform shear stresses generated in the laminar flow field of a conventional cone and plate viscometer. A range of normal fragilities was established and blood samples from patients having certain well-defined haematological abnormalities were found to be partially or completely outside these limits. The present technique is sensitive enough to distinguish between young and old cell fractions isolated from the same original population and also appears to be able to resolve discrete sub-populations having different mechanical fragilities within unfractionated samples from certain patients (e.g. macrocytosis). This technique provides additional information which could aid or facilitate diagnosis and might eventually form the basis of a routine screening test in clinical haematology.