PTH-108 The use of quantitative faecal immunochemical (FIT) testing in the streamlining of lower gastrointestinal investigations

IntroductionThe COVID-19 pandemic has resulted in a significant backlog of endoscopies, and challenges in achieving two-week-wait and eighteen-week-wait targets. Faecal Immunochemical Testing (FIT) offers a potential method to stratify the urgency of investigation by endoscopic or cross-sectional imaging. FIT scores are now used at Hillingdon Hospital during the referral triage process; patients with FIT >50µg/g being prioritised. This study aims to determine the impact of FIT testing on the post-COVID rationalisation of lower GI investigations in a real-world district general hospital setting,MethodsData was collected prospectively from January 2020 to January 2021 for all patients referred to Hillingdon hospital with lower GI symptoms and a FIT score, who were subsequently triaged to colonoscopy and/or an lower GI imaging modality (CT virtual colonoscopy or CT abdomen/pelvis with prolonged faecal tagging). We evaluated the diagnostic accuracy of FIT for colorectal cancer (CRC) and other significant bowel disease (SBD: inflammatory bowel disease, high-risk polyps as per 2020 BSG post-polypectomy guidelines) across a range of FIT thresholds (50µg/g). Multivariable logistic regression was performed to assess the predictive value of various demographic (age, gender) and clinical variables (lower GI symptoms, two-week vs non two-week referrals) in the prediction of CRC and SBD.Results481 patients (21-95 years, median 62 years) were included in the analysis. The prevalence of CRC in this cohort was 6.6%. The negative predictive values of FIT for CRC at three cut-offs (10µg/g, 50µg/g and 100µg/g) were 98.3% (95%CI 93.6-99.5%), 98.1% (95%CI 96.2-99.1%) and 96.7% (95%CI 94.9-97.9) respectively. The sensitivities at these cut-offs were 93.8% (95%CI 79.2-99.2%), 81.3% (95%CI 63.6-92.8%) and 62.5% (95%CI 43.7-78.9%) respectively. Based on a 10µg/g cut-off, two CRCs would have been missed, both of which arose in males over 75 years old. Multivariate regression analyses demonstrate that increasing age, male gender, and FIT>50µg/g are the sole of predictors of CRC (see table) and SBD.ConclusionsA combination of age, male gender and FIT values are 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 >50µg/g are prioritised as most urgent. Units with significant endoscopy backlogs could also consider de-escalating