I’d bet good money that I was simply testing myself wrong.
How well the rapid tests work depend on a few factors, but the ones I want to focus on are (a) how wet your epithelium is when you swab it and (b) how many of the virions are hanging around the section of your epithelium you swab. If you don't breathe through your nose very much (easy to do when you have a respiratory infection), you might have fewer virions in your sinuses (depending on if you have viral replication there). If your epithelium is super dry (super easy for this to occur when its infected with a virus that reduces circulation, makes the throat sore (leading to less water intake), and makes a person cough a lot), you'll transfer a lot less viral matter onto the testing swab.
There are probably videos online that can help, but if your tissue is super dry the threshold of number of virions produced by the subject per second required to register a positive probably increases.
Source: speculation mostly. I used to do research in a different but related subfield of biophysics
A positive rapid test means that you swabbed your nose and found intact covid virus particles, and enough of them to trigger a positive test. A positive PCR test could still be picking up viral RNA after the virus was eviscerated by the immune system.
So a positive lateral flow = contagious, a positive PCR means maybe contagious. A negative of either means you could still be contagious, a negative PCR being much more indicative that you have cleared the virus than a negative lateral flow.
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I think what they're getting at is that post infection you might continue to have positive test results even when you're no longer sick/contagious.
If you've got enough viral load to test positive with an antigen / lateral flow test, you're pretty much contagious.
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How well the rapid tests work depend on a few factors, but the ones I want to focus on are (a) how wet your epithelium is when you swab it and (b) how many of the virions are hanging around the section of your epithelium you swab. If you don't breathe through your nose very much (easy to do when you have a respiratory infection), you might have fewer virions in your sinuses (depending on if you have viral replication there). If your epithelium is super dry (super easy for this to occur when its infected with a virus that reduces circulation, makes the throat sore (leading to less water intake), and makes a person cough a lot), you'll transfer a lot less viral matter onto the testing swab.
There are probably videos online that can help, but if your tissue is super dry the threshold of number of virions produced by the subject per second required to register a positive probably increases.
Source: speculation mostly. I used to do research in a different but related subfield of biophysics
deleted by creator
A positive rapid test means that you swabbed your nose and found intact covid virus particles, and enough of them to trigger a positive test. A positive PCR test could still be picking up viral RNA after the virus was eviscerated by the immune system.
So a positive lateral flow = contagious, a positive PCR means maybe contagious. A negative of either means you could still be contagious, a negative PCR being much more indicative that you have cleared the virus than a negative lateral flow.