The CRC analysis identified male gender (odds ratio, OR 2.39 (95% CI 1.039–5.519), p = 0.041), iron deficiency anaemia (OR 2.99 (95% CI 1.27–7.03), p = 0.012) and f-Hb ≥ 10 μg Hb/g faeces (OR 86.60 (95% CI 11.70–641.16), p < 0.001) as independent predictors [29]. This evidence concerns the gene GSTM1 and Iron deficiency anemia.