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

Abstract

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 χ2 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.

A cohort study of duplicate faecal immunochemical testing in patients at risk of colorectal cancer from North-West England

“…As all the patients who were subsequently diagnosed with CRC following two negative tests were subsequently found to have anaemia, if FIT was performed in combination with a FBC, it is possible that almost all patients with CRC could be identified using a minimally invasive approach. This supports the strategies of combining negative FIT and lack of anaemia described by the Nottingham and Glasgow groups 23 24. While the validity of this approach will require robust evaluation, this raises the possibility that a significant proportion of symptomatic patients who are currently referred as suspected cancer patients to secondary care for colonoscopy could potentially avoid urgent referral.…”

“…This supports the strategies of combining negative FIT and lack of anaemia described by the Nottingham and Glasgow groups. 23 24 While the validity of this approach will require robust evaluation, this raises the possibility that a significant proportion of symptomatic patients who are currently referred as suspected cancer patients to secondary care for colonoscopy could potentially avoid urgent referral. Since patients with two negative FIT results have such a low chance of having a diagnosis of CRC, this provides excellent reassurance for primary care physicians and patients.…”

Prevalence of repeat faecal immunochemical testing in symptomatic patients attending primary care

“…This is the first study to examine the prevalence of serial FIT measurements in symptomatic patients and the associated rate of CRC. Serial FIT results account for almost one tenth of all test results and this cohort of patients had a lower prevalence of CRC overall than those cohorts we have described in previous studies [1, 2, 7, 16]. Those patients with two consecutive f‐Hb results <10 μg/g in a 12‐month period have a very low risk of CRC (0.1%).…”

“…and this cohort of patients had a lower prevalence of CRC overall than those cohorts we have described in previous studies [1,2,7,16]. Those patients with two consecutive f-Hb results <10 μg/g in a 12-month period have a very low risk of CRC (0.1%).…”

“…or less [2,14]. The false-negative rate of the FIT for CRC is generally reported as 5%-10% [1,7,17].…”