GSTM1 and colorectal carcinoma: The aim of this study was to use the data accumulated since the introduction of FIT in the SBoSP in order to assess the development of a more rational approach to estimating an individual's risk of harbouring CRC based on f-Hb, age, sex, deprivation as assessed by the Scottish Index of Multiple Deprivation (SIMD), NHS Board of residence and screening history.