Measurement of erythrocyte deformability by two laser diffraction methods

The aim of this work is to study the deformability of red blood cells (RBC) by two laser diffraction methods: the Laser-assisted Optical Rotational Ce ll Analyser (LORCA, Mechatronics, Amsterdam, Netherlands) and a Shear Stres s Diffractometer (RHEODYN SSD, Myrenne, Roetgen, Germany). Experiments were carried out on 46 healthy human subjects. The elongation index EI of norma l and hardened RBCs (obtained by heating blood at 49 degrees C or by incuba ting RBCs in solutions of diamide) was measured. The results showed that th e standard deviations of the experimental data for normal RBCs were relativ ely small, especially at high shear stresses (more than 3.0 Pa), but higher than those reported before. Some correlations between the results given by the two instruments were also found. It should be noted that for hardened RBCs, the standard deviations of the measurements were important compared w ith the mean values in the two instruments.