Rheological properties of sickle erythrocytes in patients with sickle-cell anemia: The effect of hydroxyurea, fetal hemoglobin, and α-thalassemia.

OBJECTIVE: Determine the effect of fetal hemoglobin (HbF) and α-thalassemia on red blood cell (RBC) deformability of patients with sickle-cell anemia (SCA) with and without hydroxyurea (HU).

METHODS: Adult patients were enrolled in the Sickle Cell Program of the Cardeza Foundation (Thomas Jefferson University) and were followed up prospectively during the period in which the Multicenter Study of Hydroxyurea (MSH) in patients with SCA was conducted. Ninety-one patients did not receive HU, 20 patients were enrolled in MSH, and 10 patients were enrolled in an open-label study of HU in SCA. Of the 20 patients enrolled in MSH, 11 took HU and nine took placebo. Control group included 113 normal individuals. Red blood cell deformability index (DI) was measured by ektacytometry.

RESULTS: Patients with SCA taking HU (n = 21) had higher DI than those taking placebo (n = 9) or who were not taking this therapy (n = 91). In patients without therapy, those with α-thalassemia (n = 31) had higher DI than those without. We showed a significant positive correlation between the level of HbF and DI. SCA patients without α-thalassemia and HbF <10% (n = 48) had lower DI than patients with α-thalassemia and HbF <10% (n = 23) and patients with (n = 8) or without α-thalassemia but with HbF >10% (n = 12). DI measured in patients without α-thalassemia and HbF >10% was higher than in the three other subgroups.

CONCLUSION: Elevated levels of HbF with or without HU and α-thalassemia improve sickle RBC rheology, which, in turn, improve the clinical picture of SCA.