The role of quantitative faecal immunochemical test (qFIT) in patients presenting with per-rectal bleeding: A cohort study from a colorectal unit in Scotland

Background and Aims The quantitative faecal immunochemical test (qFIT) is established for triaging patients with lower gastrointestinal symptoms, but its utility in those with per-rectal bleeding (PRB) requires further validation. This study aimed to: (1) evaluate qFIT as a first-line investigation for ruling out colorectal cancer (CRC) in patients with PRB; (2) assess the diagnostic yield of qFIT across different quantitative ranges; and (3) determine the positive predictive values and negative predictive values (NPVs) for CRC and clinically relevant benign bowel pathologies (BBPs). Methods A cohort analytical study was conducted (May 2022–September 2023) involving 203 patients referred via the two-week wait pathway with suspected CRC. Patients were stratified into four groups based on the presence of PRB and qFIT result (positive: ≥10 µg Hb/g). Diagnostic outcomes (CRC and BBP) were confirmed via colonoscopy, imaging, cross-sectional imaging, and histopathology where applicable. Results Of 203 patients, 76 (37.4%) presented with PRB. In the PRB group, 53 had a positive qFIT (Group 1), and 23 had a negative qFIT (Group 2). CRC was detected in 5 out of 53 (9.4%) in Group 1 and 0 out of 23 (0%) in Group 2, yielding an NPV of 100% (95% confidence interval (CI) 85.2%–100.0%) for CRC in PRB patients. Among the 127 patients without PRB, CRC was found in 13 out of 88 (14.8%) with a positive qFIT (Group 3) and 1 out of 39 (2.6%) with a negative qFIT (Group 4). In patients without PRB, qFIT positivity showed a non-significant trend towards higher odds of CRC (odds ratio (OR) 6.59, 95% CI 0.82–53.0; p = 0.07). CRC prevalence increased significantly with rising qFIT values, with patients having qFIT >400 µg/g demonstrating higher odds of CRC than those with qFIT 10–150 µg/g (OR 22.0, 95% CI 3.56–136.1; p = 0.001). The incidence of BBP remained high across all groups, including 56.5% of qFIT-negative patients with PRB. Conclusion In this cohort, qFIT demonstrated a high NPV for CRC in patients presenting with PRB. A negative qFIT in patients presenting with PRB may support risk stratification and could help reduce unnecessary colonoscopy in selected cases, but larger prospective studies are needed before firm de-escalation recommendations can be made. Patients without PRB but with high qFIT levels (>400 µg/g) should be prioritised for urgent investigation, given the high probability of CRC.