However, a different result was obtained in patients with preoperative anemia: the mean change in Hb level was significantly lower in the iron group despite the lower transfusion rate (no-iron group vs. iron group, 0.6 ± 0.9 vs. 0.1 ± 1.1, P = 0.016; Table 6). Here, GSTM1 is linked to anemia (phenotype).