GSTM1 and anemia (phenotype): Known groups validity was demonstrated with discrimination between groups (patients with varying levels of anaemia, using haemoglobin (Hb) levels at baseline) defined by SF-36 Physical Function and Vitality median split scores to FACT-An scores at baseline and FACT-An, FACT Anemia and FACT Fatigue subscale median split used to show a baseline difference to SF-36 scores.18