The document is a guideline on the use of Faecal Immunochemical Testing (FIT) for patients with suspected colorectal cancer (CRC). It is a joint guideline developed by the Association of Coloproctology of Great Britain and Ireland (ACPGBI) and the British Society of Gastroenterology (BSG). The guideline tries to establish a clear strategy for using FIT in diagnosing patients with symptoms suggesting CRC. FIT offers high sensitivity and helps prioritize patients who need urgent investigation while identifying low-risk individuals.
FIT is more accurate than symptoms alone in predicting CRC, reducing unnecessary referrals and focusing on high-risk patients.
FIT should be used in both primary and secondary care for patients with bowel symptoms. It is especially useful in triaging patients for urgent colorectal investigation based on a faecal haemoglobin (fHb) threshold of ≥10 µg Hb/g.
The guideline emphasizes access to FIT testing for general practitioners (GPs) and its role in diagnostic pathways. It also discusses the importance of safety netting, where FIT results are below the threshold but symptoms persist.
Multiple studies have shown FIT to have superior sensitivity and specificity compared to symptom-based criteria for CRC detection.
The NICE FIT study,a multicentre double-blinded study of 9822 patients undergoing colonoscopy, demonstrated that the risk of bowel cancer was around 0.2% in those with undetectable levels of fHb and 0.4% in those with fHb <10 µg Hb/g faeces.
- Recommendations:
- FIT should be used to prioritize CRC investigation.
- A threshold of ≥10 µg Hb/g should trigger referral.
- Patients should not be excluded from referral based on FIT results alone.
- The guideline supports using FIT to inform the urgency of referral in patients with anaemia or symptoms like anorectal bleeding.
Remember, FIT sensitivity and especificity depend on the prevalence of Colorectal cancer, and if other symptoms are associated (anaemia, weight loss, rectal bleeding, thrombocytosis) but as an estimate:
Cancer rate
< 0.1% for <4µg Hb/g faeces,
0.6% between 4 – 9.9µg Hb/g faeces,
3.3% for 10–99.9µg Hb/g faeces
20.7% for ≥100Hb/g faeces