Our models, which included f‐Hb, age, sex, MCV and platelet count, increased the positive predictive value for CRC compared to the f‐Hb cut off of ≥ 10 μg/g currently recommended by NICE and others, with minimal change in the negative predictive value [6, 21, 22]. The gene discussed is GSTM1; the disease is colorectal carcinoma.