Scenarios where true diagnosis is actionable (i) versus inactionable (ii). “Actionability” refers to the idea that rapid identification can reduce preventable morbidity and mortality compared to delayed identification. When the true diagnosis is actionable (scenario “i”), the perfect diagnostic strategy instantaneously actuates the increment in EVI made possible by ascertaining that diagnosis, at minimal cost. When the true diagnosis is inactionable (scenario “ii”), the perfect diagnostic strategy minimizes decrements in EVI associated with ruling out other diagnoses because of harms and/or costs associated with diagnostic tests. EVI: expected value of information.