I was in a study. My IgG titer went up to 960, when I gave plasma twice, then 7-8 months after the infection it was below the 80 threshold to be considered positive. The weird thing was that six months in, I got tested for IgM and I was positive for that as well, which might been a sign of a second exposure. I know others in the same study who were negative a few weeks after being positive. So it might depend on the person and the test.

antibody tests are really hard. his could be a false negative. further, he could have had it, but without antibodies. or he might have had something else.

If he didn’t have antibodies then how did he ever recover? Surely the thing doesn’t just burn itself out. Without anything to fight it, won’t it just continually infect him?

There are two basic immune systems: innate and adaptive. In some cases the innate immune system clears the infection before the adaptive immune system produces detectible levels of antibodies.

https://en.wikipedia.org/wiki/Innate_immune_system?wprov=sfl...

Sorry, I'm aware of that in general. I was wondering in this case. I suppose that's possible for people who don't fall sick (I assume that's why low viral load means you can get exposed and not get sick?) but OP was quite sick.

I think it’s unlikely that’s it for someone seriously ill for an extended period.

some people are recovering through other responses, including t-cell response, etc. I don't have the academic experience, the clinic experience, or his specific medical history, so I can't speak specifically. I do recall lots of papers at the beginning of Covid talking about high t-cell responses in patients without a lingering anti-body response. That all could have been early science based on poor data as well though.

Based on the information provided it seems highly unlikely the OP had covid.

It isn't impossible but the lack of antibodies is just one further data point. Most people who recover have positive antibody tests.

>antibody tests are really hard.

Are you referring to the quantitative side? You can simply buy the antibody standard and sVNT test kit from Genscript. You can get a 96 test kit for under $3k. We have it and it works quite well.

the general concept of antibody tests. Antibodies have serious dilution. Detection is a challenging problem. Many antibody tests (ex. measles) has a pretty high (in my unqualified opinion) false negative rate. Its a tough problem to solve in general.

a single paper discussing false reports - https://pubmed.ncbi.nlm.nih.gov/14574997/

Well, let me first state the obvious - no test anywhere is perfect. But when it comes to antibody tests you have to be a bit more specific and discuss the underlying technology and method of detection. For e.g. there are 1129 diagnostic products for covid, and not all of them are identical. There are many reasons for false-negatives and some could be specific to the product being used. The paper you linked to is not about COVID19, its from 2003 and also its scope is not a general review of antibody tests. Its an investigation into false-positives with a specific underlying autoimmune disease possibly masking the result. I am not familiar with this study to speak in any great detail.

https://www.finddx.org/covid-19/pipeline/