GSTM1 and colorectal carcinoma: However, given the assessed loss in detection of AN and CRC, most of them in their early stages, it may be that the f-Hb cut-off that is going to be implemented should not be change only by sex or age, at least initially, in accordance with the recommendations of the European guidelines, in order not to increase the ratio of interval cancers, which is another important variable to examine.