GSTM1 and Iron deficiency anemia: Patients selected for colonoscopy were significantly younger (median 60 vs 61 years, p = 0.02), more likely to have reported PR bleeding (44.1% vs 27.3%, p < 0.001) or persistent diarrhoea (27.4% vs 21.5%, p = 0.001), had significantly higher f-Hb (≥ 10 μg/g 52.9% vs 19.8%, p < 0.001), and more iron deficiency anaemia (8.0% vs 5.4%, p = 0.018).