Fluctuating deformability of oxygenated sickle erythrocytes in the asymptomatic state and in painful crisis.

A new gravity filtration technique for the study of sickle cell deformability has shown a significant loss of filterability of oxygenated erythrocytes on day 2 of painful crisis in eight patients with homozygous sickle cell anaemia; there was no increase in irreversibly sickled cell (ISC) count. Serial study (mean of 5.2 occasions) in six out-patients when asymptomatic also showed considerable fluctuation in sickle cell filterability with time; this was again independent of ISC count. Erythrocyte filtration methods demonstrate fluctuations in the rheology of sickle cells that are not detected by ISC counts and which are probably secondary to clinically occult, as well as overt, vaso-occlusive events in the microcirculation.