Preoperative Hb was markedly lower in the postoperative anemia group [124.4 (17.1) vs. 142.9 (13.0), p < 0.001], which correlated with lower postoperative Hb [107.8 (14.9) vs. 136.5 (9.6) in the group of patients without anemia, p < 0.001]. This evidence concerns the gene GSTM1 and anemia (phenotype).