GSTM1 and congestive heart failure: Two quantitative SRs investigating chronic heart failure patients reported that QoL, VO2max, exercise capacity and dyspnea improved significantly after a mean Hb increase of 2.0–2.1 g/dL at a mean baseline Hb of 10.7–11.2 g/dL (Ngo et al., 2009; Kang et al., 2016).