Because of the link between deformability and sickled cells, deformability can be used to evaluate the amount of sickled cells in the blood. Deformability of the erythrocytes that cause the microcirculatory distress can be demonstrated through various other hemorheological characteristics.[1] In order to determine the deformability of erythrocytes multiple factors including blood and plasma viscosity and hematocrit (a calculation of the percent of red blood cells present in the blood) are measured.[2][28]