On an individual case you’re right. But in aggregate is where the nuance lies.
E.g. If 99 out of 100 cases are false positives, and those 99 people are harmed by taking action, but the one true positive was helped, which is the better policy to pursue? Blanket screening or none at all?
This gets more complicated when there are limited resources available, eg treating the 100 people means someone else misses out.
And then there are diseases like cancer, which pretty much every human will get, if they live long enough. So screening for some types of cancer can have negative health implications on some target populations.
E.g. If 99 out of 100 cases are false positives, and those 99 people are harmed by taking action, but the one true positive was helped, which is the better policy to pursue? Blanket screening or none at all?
This gets more complicated when there are limited resources available, eg treating the 100 people means someone else misses out.
And then there are diseases like cancer, which pretty much every human will get, if they live long enough. So screening for some types of cancer can have negative health implications on some target populations.