At the lower limit of f-Hb detection, 73.7% of symptomatic patients had a negative FIT.<h4>Conclusion</h4>FSP demonstrated that FIT identified both a small group of symptomatic patients with a high risk of undiagnosed CRC for urgent investigation and the majority of symptomatic patients with a very low f-Hb who could avoid colonoscopy. Here, GSTM1 is linked to colorectal carcinoma.