GSTM1 and stage 5 chronic kidney disease: Six-month hemoglobin levels were as follows: always low (18.0%), intermediate/target (1.5%), always high (0.8%), low-amplitude fluctuation/Hb low (n = 37; 27.8%), low-amplitude fluctuation/Hb high (13.53%), and high-amplitude fluctuation (38.6%), among end-stage renal disease patients.