Prioritising better, diagnosing earlier: quantitative faecal haemoglobin and colorectal cancer risk

To evaluate the predictive performance of the quantitative faecal immunochemical test (FIT) across different clinical settings and its utility for stratifying colorectal cancer (CRC) risk.

A retrospective cohort of 3,663 patients undergoing colonoscopy was analysed. Quantitative FIT values suitable for diagnostic performance analyses were available in 2,848 patients. A stratified analysis was conducted across clinical settings (asymptomatic individuals, anaemia, rectal bleeding, constitutional symptoms, and other indications for colonoscopy). The predictive capacity of FIT was assessed, and optimal cut-off values were explored.

CRC was diagnosed in 567 patients (15.5%). FIT levels were significantly higher in CRC cases (2,113.90 vs 615.99 ng/ml; p < 0.001). In asymptomatic individuals, values above 300 ng/ml were associated with a higher likelihood of CRC. In symptomatic patients, particularly those with anaemia, CRC risk increased at values above 400 ng/ml. In patients with constitutional symptoms, a cut-off of approximately 325 ng/ml showed discriminative utility.

FIT enables context-dependent stratification of CRC risk. The context-specific cut-offs identified in this study should be considered exploratory thresholds that may help prioritise colonoscopy, rather than definitive clinical decision rules. Importantly, low FIT should not be used to exclude CRC or to defer clinically indicated colonoscopy in patients with high clinical suspicion.