Combining the quantitative faecal immunochemical test and full blood count reliably rules out colorectal cancer in a symptomatic patient referral pathway

PURPOSE: Faecal Immunochemical Test (FIT) has proven utility for Colorectal Cancer (CRC) detection in symptomatic patients. Most studies have examined FIT in symptomatic patients subsequently referred from primary care. We investigated associations between CRC and FIT in both referred and non-referred symptomatic patients. METHODS: A retrospective, observational study of all patients with a FIT submitted Aug 2018 to Jan 2019 in NHS GG&C was performed. Referral to colorectal/gastroenterology and decision to perform colonoscopy were recorded. FIT results were grouped as f-Hb < 10/10–149/150–399/ ≥ 400 μg/g. The MCN cancer registry identified new cases of CRC. Covariables were compared using the χ(2) test. Multivariate binary logistic regression identified independent predictors of CRC. RESULTS: A total of 4968 patients were included. Raised FIT correlated with decision to refer (p < 0.001) and scope (p < 0.001). With 23-month median follow-up, 61 patients were diagnosed with CRC. These patients were older (median 69 vs 59 years, cancer and no cancer respectively, p = 0.001), more likely to be male (55.7% vs 42.1%, p = 0.033), and to report rectal bleeding (51.7% vs 36.1%, p = 0.013). FIT (< 10 µg/g 8.2% vs 76.7% and ≥ 400 µg/g 55.7% vs 3.8%, p < 0.001) and anaemia (45.9% vs 19.7%, p < 0.001) were associated with CRC. On multivariate analysis, age (p = 0.023), male sex (p = 0.04), FIT (≥ 400 OR 54.256 (95% CI:20.683–142.325; p < 0.001)), and anaemia (OR 1.956 (1.071–3.574; p = 0.029)) independently predicted CRC. One patient (0.04%) with a negative FIT and normal haemoglobin had CRC. CONCLUSION: GP referral and secondary care investigation patterns were influenced by FIT. The combination of normal Hb and f-Hb excluded CRC in 99.96% of cases, providing excellent reassurance to those prioritising access to endoscopy services. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1007/s00384-021-04079-2.