GSTM1 and chronic obstructive pulmonary disease: Further clinical evaluation is required to clarify the value of this approach, especially in view of the reduced oxygen delivery capacity of HbF, as this might favour the implementation of a target Hb level higher than 10 g/dL in response to increased need (e.g. PHT, coronary heart disease and chronic obstructive pulmonary disease (COPD)) and an increased ratio of HbF/HbA.