Raising the threshold from 10 to 20 μg Hb per g resulted in modest reduction in NNI for colorectal cancer but a marked increase in missed colorectal cancers, from 6.6 to 12.5 per cent (FIT1) and 3.4 to 10.2 per cent (FITMAX). The gene discussed is GSTM1; the disease is colorectal cancer.