A laser diffraction system for the measurement of R BC deformation (i.e., Elongation Index, EI) has been evaluated and the results compared to data obtained via direct observation with a cone-plate Rheoscope; this laser system is designed to be used with a Contraves LS-30 viscometer and is based on the ektacytometric principle. When compared with the Rheoscope, EI values from the laser system are in close agreement (r = 0.965, 7 normal donors) over a shear stress range of 6.2 to 245.8 dynes/cm2. Both methods demonstrated decreasing RBC deformability consequent to increasing periods of heat treatment at 48
C, with the paired data being fitted by a Y = X relationship. In addition, the laser system clearly demonstrated the expected inverse relation between cell age (i.e., density and cell deformation. The laser system was also used to measure light transmission-shear rate relations and thus to determine the minimum shear rate necessary to induce complete RBC disaggregation (
); paired studies indicated excellent agreement between this method and results obtained with a Myrenne Aggregometer (r = 0.989, 7 normal donors). In overview, this laser diffraction system offers a useful, relatively low cost method for the measurement of RBC deformability and of RBC aggregation parameters; whole blood and plasma viscosity measurements are also possible via the associated Contraves viscometer.
