Patients were divided into the following three groups according to their hemoglobin (Hb) concentrations within 24 h after MT; no anemia (Hb concentrations ≥13 g/dL for men and ≥ 12 g/dL for women), mild anemia (Hb concentrations of 11–13 g/dL and 10–12 g/dL, respectively), and moderate-to-severe anemia (Hb concentrations <11 g/dL and < 10 g/dL, respectively). This evidence concerns the gene GSTM1 and anemia (phenotype).