Figure 1. Markov Model Schematic.

All patients began in the Markov model healthy at age 45 years, with average risk of developing colorectal cancer. If patients were not screened, as in the natural history, there was no polyp detection or polyp surveillance, and the cancer state was entered only after diagnostic colonoscopy due to symptomatic presentation. For all other strategies, screening could detect either polyps or cancer. Death was determined by age-specific all-cause mortality, or age and stage-specific cancer death.