GSTM1 and anemia: No significant differences were observed in Hb decrease of more than 2 mmol/L (RR 0.87; 95% CI, 0.70-1.08), preoperative blood transfusion (RR 0.72; 95% CI, 0.50-1.05), postoperative blood transfusion (RR 1.11; 95% CI, 0.97-1.26), PRBC units (OR 1.27; 95% CI, 0.91-1.77), or postoperative anemia (RR 1.02; 95% CI, 0.89-1.15).