Faecal immunochemical tests:Resembling a Swiss army knife

The detection of blood in feces has often been perceived as an inadequate investigation, probably because of the poor performance of the now-considered-obsolete guaiac fecal occult blood tests (e.g., Hemoccult®). Qualitative fecal immunochemical tests (FITs) performed by medical laboratories have many disadvantages and should also be considered as obsolete and discontinued. In contrast, the performance of quantitative FITs, which generate estimates of fecal hemoglobin concentration, is such that they have become widely considered as the best non-invasive investigation for use in screening programs for individuals at average risk of colorectal cancer (CRC). In France, quantitative FITs (OC-Sensor FITs at a 30 μg/g threshold for a positive test result) are reserved exclusively for the population-based CRC screening program. However, uses of FITs in other clinical applications have been evaluated and validated. FITs can be used for CRC screening in individuals allegedly at high risk, namely those with a family history of colorectal neoplasia, and in surveillance of individuals after polypectomy of 1 or 2 low risk polyps. Several neighboring countries, particularly the United Kingdom and Spain, use FITs in general practice to determine the indication for colonoscopy in patients presenting with lower gastrointestinal symptoms, and to assess the degree of urgency, with decision thresholds different from those in organized screening programs: a fecal hemoglobin concentration above 4–10 μg/g should be investigated by colonoscopy, which should be considered as urgent if the concentration is above 150 μg/g. The measurement of fecal hemoglobin has been proposed as an alternative to fecal calprotectin in inflammatory bowel disease affecting the colon in the diagnosis and monitoring of mucosal damage and healing and for the prediction of relapse. Further uses of FIT are still under evaluation and offer interesting perspectives, such as personalized screening according to sex, age, and serial fecal hemoglobin concentrations. To make the best use of the good diagnostic performance of quantitative FIT, French recommendations on CRC risk evaluation, CRC screening in individuals with a family history, and indications for colonoscopy need to be updated. Similarly, the management, organization, and specifications of the French organized screening program need to be reviewed. Lowering the positivity threshold from 30 to 20 or even 15 μg/g is proposed.