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Comment by gnfisher | Hacker News Reader

It is unclear if he was symptomatic in the first positive test. I have read at least some of the tests are capable of giving false positives. Could this have been the case here?

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It's more likely that the tests that cleared him were false negatives.

I understand that false negative PCR tests are almost impossible?

EDIT: for those down voting. What about this paper then?

https://pubmed.ncbi.nlm.nih.gov/32133832/

It's the opposite. The PCR tests are more specific (99%) than sensitive (perhaps 90%, we're not really sure).

30% chance of false negative which is why they do 2 days in a row, which bring it down to 9% chance of false negatives.

Sooo, if you release a thousand patients as cured based on these tests, you'll have 90 false negatives...

I think you have that backwards.

False negative seems extremely plausible. If you're sick, but your viral load is low, it should be possible to collect a sample without a virus particle. If the sample doesn't contain a viral particle, it will necessarily come back negative.

False positive seems unlikely, as you'd have to have something that survives several cloning cycles that ends up looking exactly like the markers you're matching against.

It’s the opposite. False positives are highly improbable. False negatives happen more regularly.

If there are very little viruses, and the swab/sample didn’t contain any you would get a false negative test.

There's a 9% chance of two false negatives in a row, so that could be the case. But why would he develop a fever so late after being first tested positive? His fever would have been 20 days after first detection of his infection.

Also, the article doesn't say whether he had fever initially and it went away and then came back, which is important information.

He's in his 70s, he could be immune compromised etc... Many reasons why his body might not have actually cleared the virus.

Possibly if he had related symptoms from another illness and then caught the disease due to exposure in the hopsital. I don't know if this is more likely than a false that sent him home from the hospital.

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