Rheologic Predictors of the Severity of the Painful Sickle Cell Crisis

Deformable sickle erythrocytes have been reported by Mohandas end Evens to be more adherent to vascular endothelium than rigid irreversibly sickled cells (ISC). To define the clinical implications of this finding we have determined genetic, hematological, clinical, and rheological characteristics of sickle erythrocytes obtained from 65 patients with sickle cell anemia and fetal hemoglobin (Hb F) levels .05). RBC deformability, determined by an ektacytometer, showed great heterogeneity among patients with three or four α-globin genes. Linear regression analyses of the data showed significant positive correlation of the frequency and severity of the painful crisis with RBC deformability (r = 0.49, P < .001), and negative correlations with the percentage of dense cells (r = –0.37, P = .002), and the percentage of ISC (r = –0.46, P < .001). We propose that the more deformable the sickle RBC are, the greater their adherence to vascular endothelium, and the more they cause vaso-occlusive crises, RBC deformability and the percentage of dense cells (or ISC) seem to have a predictive value of the frequency and severity of painful crises in sickle cell anemia.