Faecal immunochemical tests (FIT) for haemoglobin for timely assessment of patients with symptoms of colorectal disease

Many patients present in primary healthcare with symptoms of serious colorectal disease (SCD), namely colorectal cancer (CRC), advanced adenoma and inflammatory bowel disease. However, SCD is present in only a small proportion. Colonoscopy is often a scarce resource and strategies to direct investigations to those who would benefit most would be advantageous. Guaiac-based faecal occult blood tests (gFOBT) have no role to play. However, there is now significant evidence that faecal immunochemical tests (FIT) for haemoglobin have many advantages. FIT are available in qualitative and quantitative test formats. Qualitative FIT could have some merits when used at home or in general practice or clinics: there is some evidence that these can be applied in both primary and secondary healthcare settings to detect CRC and rule-out most SCD, but they have many disadvantages. Quantitative FIT provide numerical estimates of faecal haemoglobin concentration (f-Hb). Studies have shown that, at low f-Hb cut-off, this test has high sensitivity for CRC and could be used as a rule-in test and prompt rapid referral for endoscopy. Perhaps more importantly, undetectable f-Hb provides considerable reassurance that SCD is absent and further investigation may not be required. Using both point-of care and quantitative methods, f-Hb has advantages over f-C in assessment of symptomatic patients. Risk-scoring models using f-Hb and other variables associated with SCD, especially age and sex, have been advocated. Although FIT have significant merits, no test is perfect and some cases of SCD will remain undetected; consequently safety-netting is required.