A total of 1,671 patients with CKD and renal anemia from the BRIGHTEN study, who were initiated on an erythropoiesis-stimulating agent (ESA) according to Japanese guidelines for renal anemia recommending initiating treatment when the hemoglobin (Hb) level is 11 g/dL), were analyzed using the ESA resistance index-1B (ERI-1B) and the initial ESA response index (iEResI). Here, GSTM1 is linked to chronic kidney disease.