GSTM1 and anemia: [4] In a cross-sectional, US multicenter survey of 2004, the rate of anemia was much higher at 47.7% in patients with CKD.[36] The percentage of patients with Hb ≤12 g/dL increased from 26.7% to 75.5% as GFR decreased from ≥60 mL/min/1.73 m2 to <15 mL/min/1.73 m2.