New optical technique for measuring erythrocyte deformability with the ektacytometer.

The laser light scattered by erythrocytes subjected to a well-defined shear stess can be analyzed with the ektacytometer to obtain information regarding the changes in cell shape due to fluid shear. We describe an optical technique whereby an observed quantitative output derived from a mesurement of light intensity through a spatial filter is related to the change in cellular dimensions that were previously observed under similar fluid-shear conditions by use of microscopy and a cone-plate viscometer (rheoscope). We also present the predictions of a theoretical model (of the ektacytometer) based on approximations of light-scattering theory developed for nonspherical particles, and give preliminary results for the accuracy and sensitivity of this measurement of erythrocyte deformability. With this optical technique the instrumentation (ektacytometer) is made quite simple and suitable for use in the typical laboratory. This would allow a regular, quantitative assessment of this important blood cell quality, to supplement the data obtained from the complete blood count.