Colorectal cancer (CRC) is the third most common cancer in men and the second in women with an incidence of 43,350 new cases in 2018. This incidence is increasing every year. Early detection is crucial in this pathology. In France, free screening is organized by health insurance for people aged 50 to 74 years. This screening is based on an immunological test (FIT: Fecal Immunological test), which aims to detect the presence of blood in the stool. In fact, some polyps or cancers cause bleeding that is often minimal and therefore difficult or even impossible to detect with the naked eye. If this test is positive, a colonoscopy is done to check whether or not abnormalities are present in the colon or rectum. Performed under anesthesia, this examination can detect the possible presence of polyps or cancer. Recently, with the covid-19 epidemic, the investigators were faced with an extension of the delays for colonoscopies which led to delays in patient care. To prevent this, they propose to develop a blood test that would allow rapid identification of patients with colorectal cancer, requiring rapid management. This blood test will permit to have a parameter for stratifying the therapeutic care in the event of epidemia or situation that constrains the organisation of the health system.