FIT Pathways Frequently Identify IBD in Younger Patients : Br J Surg | May 2026

Introduction

Inflammatory bowel disease and Colorectal Cancer frequently present with overlapping lower gastrointestinal symptoms including rectal bleeding, altered bowel habits and abdominal pain. In the UK, symptomatic Faecal immunochemical testing is widely used in primary care to triage patients suspected of colorectal cancer. However, the extent to which FIT pathways also identify IBD, particularly in younger adults, has remained poorly characterized.

Problem Statement

Current FIT-based referral pathways are primarily optimized for colorectal cancer detection and may insufficiently account for inflammatory bowel disease risk. Whether combining FIT with faecal calprotectin (FCP) could improve diagnostic stratification for younger symptomatic patients remains uncertain.

Summary

This large population-based cohort study analyzed more than 473,000 symptomatic patients undergoing FIT testing in UK primary care between 2019 and 2023. Within one year of FIT testing, nearly 2,800 patients were diagnosed with IBD. Importantly, individuals younger than 50 years accounted for more than half of all IBD diagnoses but less than 7% of colorectal cancer diagnoses, highlighting a major age-related shift in disease probability within symptomatic FIT pathways. Elevated FIT levels were strongly associated with increased IBD risk, with a markedly higher incidence observed among patients with FIT ≥10 µg Hb/g. The highest-risk subgroup comprised younger patients with both elevated FIT and elevated faecal calprotectin, where the probability of IBD exceeded 20%. Conversely, a normal FCP substantially reduced combined CRC/IBD risk even in patients with elevated FIT, suggesting important negative predictive value for inflammatory disease exclusion. These findings suggest that IBD may be a more likely diagnosis than colorectal cancer in younger symptomatic individuals referred through FIT pathways. The study supports incorporation of routine faecal calprotectin testing alongside FIT to improve diagnostic precision, prioritize endoscopic evaluation and potentially reduce unnecessary invasive investigations in low-risk patients. Overall, the data reinforce the evolving role of combined stool biomarker strategies in modern lower gastrointestinal triage algorithms and emphasize the importance of age-specific interpretation of symptomatic FIT results.