Correlation of total CD34⁺collection with disease severity and duration of HU washout. (A) Association of self-reported number of hospitalizations in the year before enrollment and total CD34⁺ cells/kg. (B) Association of self-reported number of medications taken on a daily basis to control chronic pain and total CD34⁺ cells/kg. (C) Association of number of days hydroxyurea (HU) was held before mobilization and apheresis total CD34⁺ cells/kg. □, Participants on chronic transfusion and hydroxyurea (HU), ○, participants on chronic transfusions; ●, participants on HU.