Representative oxygen gradient ektacytometry curve. RBC deformability is continuously measured with the laser assisted optical rotational red cell analyzer (Lorrca) while the sample is gradually deoxygenated and reoxygenated. Oxygen gradient ektacytometry generates 3 key parameters: EI_max reflects deformability at normoxia; EI_min represents minimal deformability due to change in shape; and orientation of RBCs when sickling, upon deoxygenation. PoS embodies the oxygen tension when the first RBCs start to sickle. Diffraction patterns and schematic illustration of RBCs that cause the change in deformability (EI) are shown for each parameter. Parts of this figure have been created with BioRender.com.