Understanding colorectal cancer risk for symptomatic patients in primary care: A cohort study utilising faecal immunochemical tests and blood results in England

Background: A faecal immunochemical tests (FIT) cut-off of ≥10 μg Hb/g faeces is now recommended in the UK as a gateway to urgent (suspected cancer) investigation for colorectal cancer (CRC), based on an expected CRC risk threshold of 3%. Aims: To quantify the risk of CRC at FIT cut-offs by age, haemoglobin and platelet strata. Methods: A cohort study of a symptomatic CRC pathway based on primary care FIT tests in Nottingham, UK (November 2017–2021) with 1-year follow-up. Heat maps showed the cumulative 1-year CRC risk using Kaplan–Meier estimates. Results: In total, 514 (1.5%) CRCs were diagnosed following 33,694 index FIT requests. Individuals with a FIT ≥ 10 μg Hb/g faeces had a >3% risk of CRC, except patients under the age of 40 years (CRC risk 1.45% [95% CI: 0.03%–2.86%]). Non-anaemic patients with a FIT < 100 μg Hb/g faeces had a CRC risk of <3%, except those between the age of 70 and 85 years (5.26% 95% CI: 2.72%–7.73%). Using a ≥3% CRC threshold in patients