Using the faecal immunochemical test in patients with rectal bleeding: evidence from the NICE FIT study

Abstract

Aim To investigate whether the faecal immunochemical test (FIT) could safely rule out colorectal cancer (CRC) in patients with rectal bleeding (RB). Method A multicentre, double‐blinded diagnostic accuracy study in 50 National Health Service hospitals. Patients referred from primary care with suspected CRC on an urgent two‐week‐wait pathway were asked to perform FIT prior to colonoscopy. The primary outcome measure was the sensitivity of FIT for CRC in patients with RB versus non‐rectal bleeding symptoms (NRB). The secondary outcome measures included the diagnostic accuracy of FIT for CRC and other serious bowel disease. Results Of 9822 patients included in the study, 3143 (32.0%) patients were referred with RB. CRC was present in 4.7% of patients with RB versus 2.7% of patients with NRB (p2µg/g) in 44.1% of patients with RB versus 33.9% in NRB (p2µg/g compared to 0.1% when f‐Hb was not detected. Flexible sigmoidoscopy in this group would further reduce the risk of CRC to 0.03%. The sensitivity of FIT for CRC in RB vs NRB was 98.6% (95% CI 95.2‐99.8) vs 95.6% (91.5‐98.1%) for f‐Hb >2µg/g and 96.6 (92.2‐98.9%) vs 86.3 (80.4‐90.9%) for f‐Hb >10µg/g. Conclusion Faecal haemoglobin is not always detectable in patients with RB; 56% of patients had undetectable f‐Hb (<2µg/g) and CRC was present in 0.1%. The high sensitivity of FIT can be used to rule out CRC in patients with RB and triage them more appropriately for investigation.