Patients with anemia were further divided according to the severity of anemia, including 34 patients (5.2%) with severe anemia (Hb levels ≤ 80 g/L), 115 patients (17.5%) with moderate anemia (Hb levels = 81–90 g/L), 203 patients (30.9%) with mild/moderate anemia (Hb levels = 91–100 g/L), and 304 patients (46.3%) with mild anemia (Hb levels = 101–130 g/L). This evidence concerns the gene GSTM1 and anemia (phenotype).