GSTM1 and adenoma: A study by Digby et al. showed that participants with a personal history of adenoma or a family of CRC (elevated CRC risk) who returned a fecal Hb level ≤ 2 μg Hb/g had a 7.3% rate of advanced neoplasia at colonoscopy, and for those with undetectable fecal Hb (0 Hb/g), the rate was only 2.8%, which is equivalent to an overall relative risk reduction of 59.4% [40].