Since 2005, the World Health Organization (WHO) recommendation has been to reserve transfusion for those children with profound anemia (hemoglobin [Hb] ≤ 4 g/dL; Hb ≤ 10 g/dL in neonates) and in those where anemia is less severe (Hb 4‐6 g/dL) only when signs of critical illness are present. This evidence concerns the gene GSTM1 and anemia (phenotype).