The mean haemoglobin was lower in the anaemic group that underwent further investigation than those who did not (Hb 10.68 g/dl versus 11.24 g/dl, P<0.05): 33.2 % of patients with a microcytic anaemia (mean cell volume <80) did not have any markers of iron status measured. Here, GSTM1 is linked to anemia (phenotype).