Optimizing colorectal cancer screening using fecal immunochemical tests

Colorectal cancer (CRC) screening using fecal occult blood tests has been shown to lower CRC incidence and CRC-related mortality and CRC incidence by the removal of precancerous polyps and the detection of CRC in an early stage. At present, the recommended method for organised CRC screening is the fecal immunochemical test (FIT), followed by a colonoscopy if the FIT result is positive. Multiple different brands of FITs are available but their accuracy is not perfect. FIT misses 1/4 of participants with CRC and 2/3 of participants with advanced neoplasia (AN: CRC and/or advanced adenoma) when used for a single screening round. Additionally, in 40-70% of the participants with a positive FIT who undergo a colonoscopy no AN is detected. A better understanding of the factors influencing FIT’s accuracy as well as strategies to optimize CRC FIT screening effectiveness are therefore warranted. The studies described in this thesis were performed to contribute to these goals.