For example, The Correction of Hemoglobin and Outcomes in Renal Insufficiency (CHOIR) trial included 1,432 patients with CKD stages 3–4 with anemia (defined as Hb <110 g/L) and randomly arranged them to groups with a higher or lower treatment target (135 g/L vs. 113 g/L) with a study duration of 3 years. Here, GSTM1 is linked to anemia (phenotype).