Real-World Performance of FIT Triage for Symptomatic Colonoscopy: Analysis of the UK National Endoscopy Database (NED)

Background: The UK has adopted faecal immunochemical testing (FIT) to triage symptomatic colonoscopy referrals. Objective: Quantify diagnostic yield and independent effects of FIT, age, sex and symptoms on polyp and cancer detection in symptomatic colonoscopy. Design: Nationwide analysis of prospectively collected colonoscopy reports (June 2023-August 2025) from the National Endoscopy Database. Symptomatic procedures, including iron-deficiency anaemia (IDA), were identified and diagnostic yields calculated. Mixed-effects logistic regression estimated adjusted odds ratios (aORs) with age, sex, symptom group and FIT. Post-estimation margins modelled cancer yield by age, FIT and symptoms. Results: Analysis of 447,109 symptomatic colonoscopies, with FIT recorded in 202,219 (45.2%). Overall cancer yield was 1.9% (95% CI, 1.8-1.9). Cancer yield was 3.8% (95% CI, 3.7-3.9) in FIT ≥ 10, including 2.5% (95% CI, 2.3-2.7) at age 40-49 and 0.6% (95% CI, 0.5-0.7) at age 16-39; yield in FIT < 10 was 0.3% (95% CI, 0.2-0.3). FIT concentration showed a strong, graded association with cancer risk, weaker association with large polyps, and minimal association with small polyps. IDA was associated with higher cancer risk versus rectal bleeding (aOR 2.2, 95% CI, 2.0-2.3; p < 0.01). With FIT < 10, cancer yield exceeded 1% only in IDA patients aged > 80 and remained < 0.5% otherwise. A model combining FIT, age, and IDA detected > 94% of cancers while reducing colonoscopy demand by > 40%. Conclusion: This national analysis demonstrates the superiority of FIT-based triage over symptom-based referral, with FIT ≥ 10 identifying high-risk patients, including those aged 40-49, while FIT < 10 indicated very low risk.