Introduction

In the UK, FIT is offered to adults with symptoms suggestive of colorectal cancer (CRC). A positive result (>10µgHb/g) triggers a referral through a suspected colorectal cancer pathway for further investigation.¹ IBD and CRC share many similar symptoms. However, there is very limited evidence assessing the use of FIT in predicting the onset of IBD, following exclusion of CRC.

Aims & Methods

We aimed to assess the association between abnormal FIT results in symptomatic patients and the risk of new IBD diagnosis within a year, and how this varies with age and faecal calprotectin (FCP) results. This was done through a population-based observational study of all symptomatic FIT recorded in the Clinical Practice Research Datalink (CPRD) between January 2019 and June 2023 with one year follow up.² Patients with prior diagnoses of IBD or CRC were excluded. Kaplan-Meier estimates were used to assess cumulative 1-year IBD risk, stratified by age group, FIT results and FCP results.

Results

2762 (0.58%) of 473402 patients were diagnosed with IBD within 1-year of symptomatic FIT. The risk was 541/377485 (0.1%) in those with a FIT ≤10µgHb/g compared to 2221/95917 (2.3%) with FIT>10µgHb/g. A positive FIT is associated with increased risk of IBD diagnosis (p<0.001) . Table 1 summarises the 1-year risks of new IBD diagnoses within this symptomatic FIT population in strata of age and faecal calprotectin. As can be seen those with a negative FIT have a low risk of IBD diagnosis at all ages regardless of FCP. With rising FIT the risk rises in all age groups and is highest in the under 40s with a FIT >200µgHb/g and FCP >50µg/g at 38.9 % (95% CI: 34.62-43.07%). Even at this level of FIT, cumulative risk is only 3.8% (95% CI: 1.9-5.68%) when FCP ≤50µg/g. In contrast, the cumulative risk of IBD in patients age ≥70 is low, regardless of FIT levels, with 0.05% (95% CI: 0.04-0.07%) risk in those with FIT ≤10µgHb/g and 1.4% (95% CI: 1.16-1.65%) in FIT >200µgHb/g.

Conclusion

A combination of symptomatic FIT and FCP can stratify the risk of IBD diagnosis. This should lead to prioritisation of those at high risk for early colonoscopy even among the young who are unlikely to have colorectal cancer. Those with low risk of either diagnosis could be spared invasive testing.

References

1. National Institute for Health and Care Excellence. Quantitative faecal immunochemical testing to guide colorectal cancer pathway referral in primary care [DG56]. 2023 24 August 2023 15 April 2025]; Available from: https://www.nice.org.uk/guidance/DG56.
2. Clinical Practice Research Datalink. CPRD Aurum December 2024 (Version 2024.12.001). [Data set] 2024 15/04/2025; Available from: https://www.cprd.com/doi/cprd-aurum-december-2024-dataset.