The Use of Quantitative Faecal Immunochemical (FIT) Testing in the Streamlining of Lower Gastrointestinal Investigations

Aims Faecal Immunochemical Testing (FIT) offers a potential method to stratify the urgency of colonic investigations for colorectal cancer (CRC) in the symptomatic population. This study aims to determine the impact of FIT on the post COVID rationalization of lower GI investigations in a real-world district general hospital setting.

Methods Single-centre prospective study conducted at our Hospital between January 2020 and September 2021. All patients with lower GI symptoms and a FIT score referred via the Two Week Wait (TWW) pathway who were subsequently triaged to colonic investigations (colonoscopy, CT virtual colonoscopy or CT abdomen/ pelvis with prolonged faecal tagging) were included in the analysis. The diagnostic accuracy of FIT for CRC and significant bowel disease (CRC, inflammatory bowel disease, high risk polyps) was assessed. Multivariable logistic regression was performed to assess the predictive value of demographic (age, gender) and clinical variables (individual lower GI symptoms and high-risk symptoms meeting NICE NG12 TWW referral criteria) in the prediction of CRC and SBD

Results 1098 patients (18-101 years, median 62 years) were included in the analysis. The prevalence of CRC in this cohort was 5.6%. The negative predictive values of FIT for CRC at three cut-offs (10 μgHg/g, 50 μgHg/g, 100 μgHg/g) were 98.9% (95% CI, 96.6 to 99.6), 97.7% (95% CI 96.6 to 98.4) and 96.8% (95% CI 95.8 to 97.6) respectively. Multivariate logistic regression demonstrates that increasing age (odds ratio 1.06; 95% CI 1.04 to 1.09) and a FIT>50 µg/g (odds ratio 12.48; 95% CI 3.75 to 41.62 respectively) are the sole of predictors of CRC

Conclusions A combination of age and FIT value are the most predictive variables of future CRC and SBD risk. In the current post COVID environment, FIT can play a role in streamlining lower GI investigations for two-week referrals, where FIT above 50 µg/g are prioritised as most urgent. Units with significant endoscopy backlogs should consider de-escalating two-week referrals of younger patients with low FIT values less than 10 µg/g.

Conflicts of Interest

Authors do not have any conflict of interest to disclose.

Publication History

Article published online:
27 March 2025