GSTM1 and colorectal carcinoma: A study performed in Scotland demonstrated that an abnormal (positive) guaiac faecal occult blood test (gFOBT) result, which can be considered as a marker for elevated f-Hb, was shown to be associated with an increased risk of death, not only from CRC, but also from all-causes, cardiovascular disease, respiratory disease, digestive disease, neuropsychological conditions, and endocrine disease [20].