All 40 participants with anemia (hemoglobin (Hb) <12.5 g/dl, transferrin saturation <20%, ferritin <100 ng/ml) in a setting of chronic heart failure (LVEF < or =35%) or chronic renal failure (creatinine clearance <90 ml/min) were either given IV iron therapy or a placebo, at random, for five weeks after which they were evaluated on the based on Minnesota Living with Heart Failure Questionnaire (MLHFQ) and 6-min walk (6MW) test [48]. This evidence concerns the gene GSTM1 and anemia (phenotype).