The measurement of erythrocyte deformability using micropore membranes. A sensitive technique with clinical applications.

This article describes a positive-pressure filtration technique using low pore-density, 3 microns pore-diameter polycarbonate membranes employed to evaluate erythrocyte deformability in a clinically oriented hematology laboratory. Mean erythrocyte resistance to filtration was expressed by a numerical index which takes into account both the initial resistance of dilute red cell suspensions to passage across the membrane and the relative pressure rise observed after filtration of 30 ml of the same suspension (3 . 10(8) cells). The resistance index of 99 blood samples obtained from 88 healthy adult volunteers ranged between 1.4 and 2.9, with normal Gaussian distribution and mean of 2.04. Values obtained on similarly prepared samples from 20 patients with various hemolytic anemias always fell outside this range, indicating a reduced deformability in every case. The existence of a strong positive correlation was found between the resistance index and the degree of reticulocytosis in these patients. This method appears more sensitive than previously described filtration techniques in detecting the presence of small numbers of poorly deformable erythrocytes in vivo, while being more practical and statistically more significant than the micropipette elastimetry technique. Our results, however, raise a new question concerning the role of reticulocytes in the evaluation of red cell deformability on blood samples from patients with hemolytic anemia.