I'm trying to figure out what tests they used. PCR is very specific but only works reliably in the early stages and generally has a high false negative rate.
Antibody tests only work after several days of infection, but some of them are not very specific to SARS-CoV2 and therefore have a high false positive rate.
So you really need use both tests, but you can't just OR the results together, because then a faulty antibody test will massively skew the results upward.
No, it only works if there is enough virus to be detected. If you are infected, you will have a high enough count to be detected. Each type of PCR test is highly selective. The point of them is that they can differentiate between many types of virus, depending on how its setup.
> Antibody tests only work after several days of infection
Yes. Depending on the type of test, and how its done. it can be up to a month before these tests are accurate.
In principle yes, but The PCR test is usually a throat swab, where detectable amounts often disappear after a few days, even in severely symptomatic cases.
This is the reason why China started to accept clinical diagnosis like chest scans, causing a sudden big spike in cases.
Antibody tests only work after several days of infection, but some of them are not very specific to SARS-CoV2 and therefore have a high false positive rate.
So you really need use both tests, but you can't just OR the results together, because then a faulty antibody test will massively skew the results upward.