GSTM1 and anemia (phenotype): Previous studies have also suggested that the diagnostic accuracy of FIT is lower in patients with anaemia, but this was not found to be the case in iron deficiency or iron deficiency anaemia.21,23 In line with the qFIT pilot study, the optimal cut-off value for those patients with abdominal pain was set lower at 10 μg Hb/g faeces.32 Lastly, only in the small subgroup of patients who had an abdominal mass did FIT achieve a sensitivity of 100% (see Supplementary Table S6).