[manicdee]

The ethical argument is that failure to detect a life threatening condition in 100 people is not the same evil as causing a life threatening condition in 1.

What it boils down to is the rate of false positives versus the rate of undetected positives (as opposed to false negatives). If, for example, the Apple Watch in use by 1000 people detects 3 people who with a-fib who previously were not aware of their condition, we might say, "excellent!" But on the other hand if it turns out that one of those people didn't have a-fib, was put on medication and suffered complications, we now have 1 person needlessly suffering who wouldn't have been suffering before and 2 people who are in no better or worse shape than they would otherwise have been. If the regular detection rate of a-fib leads to about 1 person in 1000 being granted an improved quality of life, has the a-fib detection program been useful or harmful?

Then it gets worse: what if the test we use to "diagnose" a condition have a high false positive rate? One example is screening for lung cancer: the screen itself has a 35% false positive rate, but the condition has a 2.1% fatality rate in the population. If you don't screen at all, 21 people in 1000 will die from lung cancer. If you screen, you end up saving about 10% of the people with lung cancer (about 3 out of that group of 21). But the screening means over 350 people end up being told they have lung cancer when they don't, 25 people end up being subject to an invasive procedure to diagnose the condition, and 3 (otherwise healthy but falsely diagnosed) people develop a major complication as a result of the invasive procedure.

Is all that harm done worth saving three lives?

The above is illustrated in this paper about lung cancer screening: https://t.co/YlbZIraekL