However, with a reassurance threshold of <7 μg/g, a CRC risk of 3% is reached at the 7–249 μg/g f-Hb range, so that a threshold for urgent referral of ≥200 μg/g could be employed, and, using the same logic, with a reassurance threshold of <10 μg/g, the threshold for urgent referral would be ≥100 μg/g. This evidence concerns the gene GSTM1 and colorectal carcinoma.