Values are means ± SD. All patients were at steady state at the time of the study, ie, no blood transfusions in the previous 3 months and absence of acute episodes at least two months before inclusion into the study. Measurements of 4 hemolytic markers (BIL, bilirubin; LDH, lactate dehydrogenase; AST, aspartate aminotransferase; RET, reticulocytes) were performed using standard methods, and a principal component analysis was used to derive a hemolytic component value from these markers.⁹  This standard statistical data reduction approach uses conventional clinical measurements to explain the maximum-shared variance among these indirect measures of hemolysis. The hemolytic component has recently been demonstrated to reflect intravascular hemolysis,⁹  had a mean of 0 (standard deviation = 1.0), and predicted 49.2% of the variation among all 4 measured variables (eigenvalue = 1.97). Blood viscosity, RBC deformability, and aggregation properties were determined as previously described.¹⁰  Polymerase chain reaction (Gap-PCR) was used to detect the 6 common α-thalassemia deletions, including −α^3.7 and −α^4.2 alleles, and triplication defects of the α-globin genes.

HbF, fetal Hb; Hct, hematocrit; MCHC, mean corpuscular hemoglobin concentration; MCV, mean cell volume; PLT, platelets; VOC, vaso-occlusive crisis; WBC, white blood cell; ηb, blood viscosity.

Significant difference between the 2 groups: *P < .05; **P < .01; ***P < .001.