A positive predictive value of 20% is considered very good for screening tests in a population of relatively normal risk.

“now we're talking about something where we're approaching one or two uh positive tests will ultimately lead to a cancer diagnosis that's that's potentially actionable so it's um I think sometimes when people hear 40% they say gee that means there's still uh um a fair amount of um uh people who are going to get a a a positive test meaning a cancer signal detected and ultimately not but again for screening tests that's incredibly high yield”