Measurement of erythrocyte deformability by radial spreading rheometry

Abstract

A new instrument (Radial Spreading Rheometer) has been deve loped to measure the radial spreading time of a concentrated washed erythrocyte suspension through a horizontally suspended filter paper. A calibration time (CT) for radial spreading of buffer was used to calibrate individual filter papers. The radial spreading time (RST) for washed erythrocytes was then expressed as the ratio RST/CT and adjusted to a standard packed cell volume of 0.50 (50%). The ratio RST/CT was independent of (a) temperature within the range 20–35°C, (b) leucocyte count up to 5.0 × 10⁹/l, and (c) platelet count up to 76 × 10⁹/l. The ratio RST/CT correlated significantly (r = 0.418, P < 0.05) with erythrocyte mean cell haemoglobin concentration but not with mean cell volume. Radial spreading rheometry is a low-cost technique for measuring erythrocyte deformability by bulk flow of a concentrated cell suspension through the wide channels of paper filters.