Sure. I'm aware of the difficult tradeoffs of screening. But the fact that screening tests X and Y are not worth doing isn't really adequate to write off a whol

Sure. I'm aware of the difficult tradeoffs of screening. But the fact that screening tests X and Y are not worth doing isn't really adequate to write off a whole new world of additional screening tests, many of which would have very different tradeoffs. (Olfactory tests are far less invasive, for one.) It's also something of a UX issue. Nobody is going to write an app that rings the cancer alarm after one positive. People might write an app that sends raw results to your doctor or medical monitoring service, and you get an email requesting an appointment to discuss your latest status. And if your breath results say that you're gonna die in the next 10 days and there's nothing to be done (exaggerated for effect), well then... maybe it won't send an email after all.