The available guidelines for perioperative blood transfusion are limited, butthe risks and benefits of this measure should always bequestioned.547Traditional practices, such as correction of preoperative anemia for normalor near-normal values of hemoglobin concentration (Hb ≥ 12 g/dL) toprepare patients for surgery, are not supported in the literature and arenot recommended in clinical practice.546. This evidence concerns the gene GSTM1 and anemia (phenotype).