Demographics and Medical Variables
Demographic information including age at the most recent clinic visit,
gender, ethnicity and type of insurance as proxy for socioeconomic
status were extracted from the EHR. Baseline disease information
included the genotype, baseline hemoglobin level, hematocrit and
absolute reticulocyte count. Treatment variables included both
hydroxyurea and chronic transfusion therapy. Hydroxyurea was included as
a treatment if the medication had been prescribed to the patient
although compliance of the medication was not factored. Chronic
transfusion therapy was for patients with history of stroke, abnormal
TCD, severe acute chest syndrome or severe pain. Disease complications
such as acute chest syndrome, stroke and avascular necrosis were
extracted by hand from the medical record.