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.