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Colorectal cancer screening occurs broadly in two settings, termed “organized” and “opportunistic.” Organized programs are typically run by nations or health care systems and usually rely on a single screening test, which is most often the fecal immunochemical test (FIT). In the opportunistic setting, screening occurs as a result of an interaction between a provider and patient. Screening can be offered as sequential testing (one test is offered, usually colonoscopy; if declined, a second test is offered, usually FIT), a choice of tests (called “multiple options”), or risk stratification (low-risk patients are offered FIT; high-risk patients are offered colonoscopy). 

Many guideline groups endorse the multiple options approach, though randomized trials show that offering as many as 5 options is no better than offering 2 options. Further, despite the widespread endorsement of multiple options as the best approach, randomized trials comparing sequential testing to multiple options have consistently shown that overall adherence is as high with sequential offers as multiple options, and more patients undergo colonoscopy (or another test offered first) with sequential offers.

In the second randomized controlled trial to compare sequential testing to multiple options in which the first test in the sequential arm was colonoscopy, 12,485 patients were randomized to receive colonoscopy only, a sequential offer of colonoscopy and then FIT, or the choice between colonoscopy and FIT. Participation rates in any test (completion of the test within 18 weeks of invitation or initial contact within that time and completion later) among the arms were lower with colonoscopy alone (17.5%) than sequential testing (25.8%) or multiple options (26.5%). Advanced neoplasia was detected in 1.1%, 1.1%, and 1.2% of participants, respectively. Primary colonoscopy was performed in 15.9% of the patients from the sequential arm and 8.5% of the patients with multiple options.