FIELD: medicine; laboratory analysis techniques. SUBSTANCE: decalcified filter is coated with sodium-chloride solution and 60% erythrocyte suspension, intensity of spot coloring with 60% erythrocyte suspension is visually estimates, and if uneven deformation of spot-constituting erythrocytes is detected, that is, if there is circular slightly-colored area in center of spot surrounded by light-color peripheral ring and a clear boundary is noted between lateral ring and central area of erythrocyte suspension spot, width of peripheral ring of erythrocyte suspension presented by negligible quantity of most deformable erythrocytes is determined. Then index of erythrocyte deformability is calculated from following formula: 
where Z is index of erythrocyte deformability; Der is diameter of erythrocyte suspension spot; PRWer is width of peripheral ring of erythrocyte suspension presented by negligible quantity of most deformed erythrocytes; Dscs is diameter of sodium-chloride solution spot. EFFECT: enhanced sensitivity, facilitated procedure, unbiased estimation of erythrocyte deformation. 2 cl, 1 dwg
