[In current practice, what is the best test to detect blood in the stool ?]

"In current practice, what is the best test to detect the presence of blood in faeces? Testing for the presence of blood in faeces is still widely performed in France, although the uptake in the national colorectal cancer screening programme is less than desirable, as is use in routine practice to guide diagnosis when patients present with gastrointestinal or general symptoms. Guaiac-based tests (Hemoccult) are obsolete and have been replaced by faecal immunochemical tests (FITs), both quantitative (OC-Sensor), currently reserved for the screening programme, and qualitative, performed by all medical laboratories. However, qualitative FITs should be abandoned: their visual reading is subjective, their positivity rate is highly variable, around 50%, and their diagnostic sensitivity for colorectal cancer has not been well determined. In contrast, quantitative FITs are reliable and their performance has been well evaluated. Several neighbouring countries use these tests in general practice to assess the risk of colorectal cancer in symptomatic patients and to determine the indication for colonoscopy. In this context, the decision thresholds are very different from those of organised screening: a faecal haemoglobin concentration below 4-10 µg/g is associated with a very low risk of cancer, a concentration above 4-10 µg/g should be investigated by colonoscopy, and a concentration above 150 µg/g requires an urgent colonoscopy."