What Antibody Studies Can Tell You — and More Importantly, What They Can't
"Let's say you're running a sero-survey among 1,000 people and only 4% of the population is actually infected. Presume the test correctly identifies positives 100% of the time, meaning it is 100% "sensitive" in scientific parlance.
There are 1,000 people in your sero-survey.
But say the test is 95% "specific," meaning that it returns false positives 5% of the time. Then among the 960 people who are truly negative, 48 people would get a false positive.
In this scenario, more people would get a false positive result than a true positive."
https://www.propublica.org/art...
Very good article, well worth to read in its entirety.
