Advantages and limitations of faecal immunochemical testing in colorectal cancer

Physicians of old have long recognised the importance of biological material for diagnostic purposes. One such example being the recognition of blood in faeces and the possibility of significant disease. This has since led to the development of stool testing for the detection of blood, from chemical-based reactions (guaiac reduction-based test) through to antigen–antibody interactions such as the faecal immunochemical testing (FIT). FIT has proven to be robust in terms of the evidence around its preanalytical and analytical use. As with any test however, when applied in a heterogenous population, its performance can be variable. Nonetheless, its accuracy for the detection of colorectal cancer, in both the screening and symptomatic population, appears consistent and acceptable as a triage tool—which is impressive. There are clinical dilemmas in the utility of FIT; for example, use in iron deficiency anaemia, variation of threshold within screening population, utility in high-risk and low-risk populations, replicate and repeat testing and FIT above threshold with normal colonoscopy. The evidence base remains unclear, and some are conflicting; hence, no clear guidance can be proffered, save clinical judgment. Combination therapy—with other markers—holds promise and its use within a reconfigured clinical pathway, attention to health inequalities, coupled with robust cost-utility analysis will ensure that FIT (alone and/or in combination with other markers) can continue to have a role—more so in the community.