Our results show that the need for RBC transfusion in the perioperative period is directly related to the value of preoperative Hb, even in the absence of a defined anemia; subjects with Hb < 13.2 g/dL required an average transfusion of 3.1 units of RBCs, while if hemoglobin was > 16.1 g/dL, the required RBC units dropped to 0.6. This evidence concerns the gene GSTM1 and anemia (phenotype).