Centers: #1 and #2 were dialysis centers while #3 and #4 were self care dialysis units.(BMI: body mass index; BP: blood pressure; CKD chronic kidney disease; Hb: haemoglobin; hs-CRP: serum high-sensitive C-reactive protein; LTI: lean tissue index; MVF: maximal voluntary force; nPCR: normalised protein catabolism rate; SMM: skeletal muscle mass; SMMI skeletal muscle mass index. The gene discussed is GSTM1; the disease is chronic kidney disease.