Decitabine increased fetal hemoglobin levels (HbF) in all treated patients. (A) Flow cytometric analysis for F cells (RBCs expressing high levels of HbF). The F-cell percentage is the proportion of gated RBCs with HbF expression similar to that of the cord blood positive control. (B) Change in F-cell percentage with treatment. (C) The peak HbF values with decitabine treatment (light gray bars) were higher than those measured during previous treatment with hydroxyurea (dark gray bars) for between 4 and 36 months. Peak HbF levels were not measured in UPN 2 during hydroxyurea treatment.