Hb is an independent predictor of OEF and CBF. Univariate correlations with Spearman’s rank test (ρ) of Hb (A) and Hb S percentage (B) with OEF and of Hb (C) and Hb S percentage (D) with CBF. Light lines connect individual patient values before and after transfusion. Blue lines indicate group-level regression. (E) Multivariate modeling of OEF and CBF as functions of Hb, Hb S percentage, age, and sex retain Hb (OEF and CBF) and age (CBF) as independent predictors. SE, standard error.