Impact of cancer prevalence on screening efficiencies. A, Exponential relationship between cancer prevalence and the number of patients needed to be screened to detect a single-cancer (NNS). Estimated NNS is plotted for cancers at individual gastrointestinal organs (only colorectal screening is currently practiced), for combined gastrointestinal cancers (Pan-GI), and for all cancer types in aggregate (Universal). For this illustration, detection sensitivities of 100% were assumed in calculations of NNS. B, Influence of cancer prevalence on positive predictive value (PPV) at various specificities. Originally published by Nature Publishing Group as Ahlquist DA. Universal cancer screening: revolutionary, rational, and realizable. NPJ Precis Oncol. 2018 Oct 29;2:23 (ref. 23) and used according to NPG's policy for Open Access articles (https://support.nature.com/en/support/solutions/articles/6000217050-use-of-an-open-access-figure-or-table).