GSTM1 and anemia (phenotype): For both the venous and capillary samples, anemia was defined as Hb concentration <12 g/dL, mild anemia as 11 g/dL ≤ Hb < 12 g/dL, moderate anemia as 8 g/dL ≤ Hb < 11 g/dL, and severe anemia as Hb < 8 g/dL.