Red blood cell deformability as a predictor of anemia in severe falciparummalaria

Decreased erythropoiesis and increased clearance of both parasitized and no ninfected erythrocytes both contribute to the pathogenesis of anemia in fal ciparum malaria. Erythrocytes with reduced deformability are more likely to be cleared from the circulation by the spleen, a process that is augmented in acute malaria. Using a laser diffraction technique, we measured red blo od cell (RBC) deformability over a range of shear stresses and related this to the severity of anemia in 36 adults with severe falciparum malaria. The RBC deformability at a high shear stress of 30 Pa, similar to that encount ered in the splenic sinusoids, showed a significant positive correlation wi th the nadir in hemoglobin concentration during hospitalization (r = 0.49, P < 0.002). Exclusion of five patients with microcytic anemia strengthened this relationship (r = 0.64, P < 0.001). Reduction in RBC deformability res ulted mainly from changes in unparasitized erythrocytes. Reduced deformabil ity of uninfected erythrocytes at high shear stresses and subsequent spleni c removal of these cells may be an important contributor to the anemia of s evere malaria.