The hepatic rSO2 of patients with severe anemia undergoing HD was low, but it improved significantly in response to the increase in Hb following an intradialytic blood transfusion (hepatic rSO2, from 46.7 ± 1.7% to 55.4 ± 2.0% before versus after intradialytic blood transfusion), and changes in hepatic rSO2 were positively and significantly associated with the transfusion-induced Hb increase [10]. This evidence concerns the gene GSTM1 and anemia (phenotype).