In the propensity-matched cohort, preoperative Hb was markedly higher in the not preoperative anemia group than in the preoperative anemia group (133 ± 12.1 g/L vs. 98 ± 14.2 g/L, P<0.001, n=1690 in each group, Table 1 and Figure 2A). This evidence concerns the gene GSTM1 and anemia.