The advantages of using FIT for colorectal cancer screening

Colonoscopy plays the central role in the detection of colorectal neoplasia. In some jurisdictions, colonoscopy is offered as the initial screening test in persons at average risk of colorectal cancer (CRC). In jurisdictions that have implemented organized, population-based CRC screening, colonoscopy is used as the diagnostic test in those with a positive fecal immunochemical test (FIT). FIT is an immunoassay specific for human hemoglobin. FIT is more senstive than gFOBT for detecting colorectal neoplasia and the amount of hemoglobin in the fecal sample can be quantitated. This is a tremendous advantage, as it allows screening programs to decide what "cut-off" in fecal hemoglobin defines a positive test. Cut-offs differ across programs depending on the FIT product used, and most importantly, colonoscopy capacity. Compared with colonoscopy, FIT is less sensitive for detecting advanced adenomas in one-time testing, or a single round of screening. However, when FIT is repeated annually or biannually, FIT sensitivity approaches that of colonoscopy after several rounds of screening. Further, FIT screening achieves higher participation than screening colonoscopy, when choice is offered. For population-based, organized screening programs, using FIT as the initial screening test has very clear advantages.