This is an important property because erythrocytes must change their shape extensively under the influence of mechanical forces in fluid flow or while passing through microcirculation (see hemodynamics).
In human RBCs there are structural supports that aid resilience, which include the cytoskeleton: actin and spectrin that are held together by ankyrin.
Sickle-cell disease is characterized by extensive impairment in erythrocyte deformability, being dependent on the oxygen partial pressure.
While the clinical implications are still being explored, deformability can be indicative of quality or preservation thereof for stored RBC product available for blood transfusion.
[citation needed] Ektacytometry based on laser diffraction analysis is a commonly preferred (and a fairly direct) method for measuring deformability.
[citation needed] Erythrocytes/RBC may also be tested for other (related) membrane properties, including erythrocyte fragility (osmotic or mechanical) and cell morphology.
Fragility testing involves subjecting a sample of cells to osmotic and/or mechanical stress(es), then ascertaining how much hemolysis results thereafter, and then characterizing susceptibility to or propensity for stress-induced hemolysis with an index or profile (which can be useful to assess cells' ability to withstand sustained or repeated stresses).