Application of diffractometry and a linear image sensor to measurement of erythrocyte deformability

We applied laser diffractometry and a linear image sensor to measurement of erythrocyte deformability to detect the light intensity pattern of the diffraction image. Deformability was evaluated as the deformability index (DI), calculated from the width and length of the diffraction pattern ellipse, estimated by the linear image sensor. With the erythrocytes under various shear stresses, the DI was linearly related to results by the geometric method (r = 0.996, p < 0.01). The coefficient of variance of DI at a shear stress of 236 dynes/cm2 was 0.2% (seven human blood samples), which was satisfactory for practical use. The DI was independent of the erythrocyte concentration in the range of 1.5 x 10(7)-5.0 x 10(7) cells/ml of suspension. Correlation between the DI and the logarithm of shear stress was linear in the range of 5 to 350 dynes/cm2 of shear stress in suspension media of different viscosities. Heat-treatment, which decreased membrane flexibility, caused parallel reduction of the DI plotted against the logarithm of shear stress. The method was sensitive and gave reproducible results. It may be useful for clinical applications.