Patients without preoperative anemia showed similar results to those obtained in the overall patients: the no-iron group showed a higher transfusion rate and a higher Hb level on POD-5 of the first and second TKA, but had similar Hb level on POW-6 and Hb level change to the iron group (Table 5). The gene discussed is GSTM1; the disease is anemia (phenotype).