[Detection of faecal blood outside organised screening programmes: the vital role of medical biologists].

Outside organised colorectal cancer (CRC) screening programmes, faecal occult blood testing helps general practitioners decide whether to refer symptomatic patients for a colonoscopy. In France, practices vary widely, have not been evaluated, and are based on several qualitative and quantitative faecal immunochemical tests (FITs) with very different performance characteristics that clinicians do not appreciate. In the United Kingdom, this practice is generally based on two recommended automated quantitative FITs and usually follows very specific recommendations. Quantitative FITs have been extensively evaluated and have demonstrated their superiority, both in organised CRC screening programmes and in the investigation of symptomatic patients, albeit with different decision thresholds. In a symptomatic patient, the threshold of 10 μg haemoglobin/gram of faeces (μg/g) from the English guidelines is not applicable in France. We suggest a threshold of 2 μg/g, offering a sensitivity of 94.7 % for the diagnosis of CRC, which must be confirmed by further studies in the French symptomatic population. The advantages of quantitative faecal immunochemical tests (FIT) are such that they will gradually replace qualitative FITs: self-collection, a single sample, at most two, lower cost, control of the pre-analytical phase, automation, a significant reduction in equivocal and uninterpretable results, control of the positivity threshold, information on the degree of urgency of colonoscopy, better analytical and clinical performance, and better cost-effectiveness ratio. It is urgent that the French National Authority for Health (HAS) draw up recommendations and a framework for use in symptomatic patients and update the nomenclature of medical biology procedures.