The TREAT study, in patients with type 2 diabetes, CKD stage 3/4 (i.e. not receiving haemodialysis), and anaemia, randomised more than 4000 patients to one of two treatment arms: darbepoetin alfa to achieve a Hb level of approximately 13 g/dL or placebo, with rescue darbepoetin alfa when the Hb level was <9.0 g/dL [4]. The gene discussed is GSTM1; the disease is anemia (phenotype).