GSTM1 and chronic kidney disease: HRQoL Scores by Hb level and CKD stage are presented in Table 2, with the patients divided into three groups according to their renal function; CDK 3a, with GFR range 45–59 ml/min/1.73 m2,CKD 3b,with GFR range 30–44 ml/min/1.73 m2 and CKD 4, with GFR range 15–29 ml/min/1.73 m2.