Relevant Medical Variables
Chart abstraction was used to obtain specific SCD genotype, overall hemoglobin, sickle hemoglobin, fetal hemoglobin, and mean corpuscular volume (MCV), with all lab values taken +/- 45 days of testing. In addition, for participants who had undergone a TCD, the most recent values for left and right middle cerebral artery (MCA) arteries were included as this is a region of heightened risk for stenosis and silent stroke35. Disease genotype was used as a proxy measure of disease severity, as Hemoglobin SS disease (HbSS) and Hemoglobin S beta zero thalassemia (HbSB0) are typically characterized as more severe forms of disease while Hemoglobin SC disease (HbSC) and Hemoglobin S beta plus thalassemia (HbSB+) are considered less severe disease subtypes1. Overall hemoglobin, sickle hemoglobin, fetal hemoglobin, and mean corpuscular volume were included given evidence of an association between anemia and neurocognitive performance5,8,36. Mean corpuscular volume (MCV) was also included in analyses as a crude indicator of hydroxyurea compliance37.