GSTM1 and anemia (phenotype): In contrast to recommendations for patients with HD-CKD, anemia treatment guidelines recommend a trial of oral iron before i.v. iron treatment in patients with ND-CKD [5] although a meta-analysis of six studies (treatment duration 22 days to 6 months) showed significantly greater levels of Hb and serum ferritin in i.v. iron compared to oral iron-treated patients [25].