For symptomatic patients, NICE advises that those with a FIT result ≥10 μg Hb/g faeces are referred on for further diagnostic testing; of these about 7% will be diagnosed with CRC.2 9 In contrast, England uses a cut-off of 120 μg Hb/g in asymptomatic screening to select who requires further investigation.11 Variations in thresholds are due to the differences in risk between asymptomatic and symptomatic populations; the risk of cancer is higher for those with symptoms therefore the threshold for further investigations is lower. This evidence concerns the gene GSTM1 and cancer.