Pre-operative Hb was 144 g/L (SD 9) in the non-anaemic group, 119 g/L (SD 9) in the treated anaemia group and 119 g/L (SD 12) in the untreated anaemia group (p-value < 0.001 for t-test comparing patients with and without anaemia). Here, GSTM1 is linked to anemia (phenotype).