[Erythrocyte deformability: critical evaluation of the study methods]

The rheological behavior of red cells in macrocirculation and in capillaries is briefly described. The following methods measuring red cell deformability are critically evaluated: a. degree of red cell 'packing' after centrifugation; b. single erythrocyte passage through microchannels (micropipette technique, rigidometer); c. filtration techniques of washed red cells; d. polymicroviscosimetry (paper filtration, filtrometer) and viscosimetry (ektacytometer). It is considered the adequacy of each method in assessing the different factors responsible for the variations of red cell deformability (internal viscosity, surface area/volume ratio, viscoelastic properties of the membrane.