GSTM1 and stage 5 chronic kidney disease: Abbreviations RBC: red blood cell; HD: hemodialysis; rhu EPO: recombinant human erythropoietin; ESRD: end-stage renal disease; EPO: erythropoietin; ROS: reactive oxygen species; CKD: chronic kideny disease; ESAs: erythropoiesis-stimulating agents; HIF-PHD: hypoxia-inducible factor prolyl hydroxylase; CO: carbon monoxide; Hb: hemoglobin