GSTM1 and colorectal cancer: Although f-Hb concentration has been already shown to predict the occurrence incident colorectal neoplasm and mortality of colorectal cancer, treating the value of f-Hb as ordinal data type has been scarcely addressed until several recent studies have found the feasibility of treating f-Hb as ordinal data type rather than only the dichotomous variable for the use in a qualitative manner.