11 ms·
Predictors of Nonseroconversion after SARS-CoV-2 Infection
- musha68k 5y agovia: https://mobile.twitter.com/ahandvanish/status/1432411002688184320 https://mobile.twitter.com/ahandvanish/status/14324110026881...
- ALittleLight 5y ago"We studied 72 persons, all of whom had a previous positive RT-PCR test but were symptom-free for >3 weeks before blood was collected for testing (Table)." Reading this page I'm not sure how they are handling the possibility of false positives. That is, some percentage of their 72 persons with a positive PCR test were actually false positives and never had the disease and thus don't have antibodies. Just googling for "RT-PCR covid false positive" turns up this result[1] which says "They combined the results of multiple studies (some looked at PCR testing for SARS-CoV-2 specifically, and some looked at PCR testing for other RNA viruses). They found false positive rates of 0-16.7%, with 50% of the studies at 0.8-4.0%." If you assume 1% false positive rate, and 80 million tests[2], then that means 80,000 are false positives. 6,873,739 total positive tests, so false positives should make up ~12% of positive cases. Given the range of possible values for the false positive rate it seems reasonable to me to suspect that this might be entirely or mostly explained by false positive rate. Unless I've missed something where they account for this. edit: From their appendix: "While we cannot formally exclude false positive RT-PCR results for some participants, PCR contamination is highly unlikely as an explanation for our findings for several reasons. First, serologic non-responders were identified by three different diagnostic laboratories (Appendix Table 1), all of which employed stringent quality control measures to guard against false-positive results. Second, we were able to independently amplify SARS-CoV-2 sequences from a subset of the original nasal swab material. Analyzing 4 samples from seropositive and 8 samples from seronegative persons (Appendix Table 1), we amplified full-length spike genes with intact open reading frames from four specimens, including two from seronegative persons (Appendix Figure 5). Finally, RT-PCR positive seronegative persons have also been identified by several other groups" Not really sure how to integrate their explanation with my intuition described above. If samples were contaminated that might explain why repeat testing of the samples continued to show infection. I feel like this definitely merits a follow up investigation with a larger sample size than 71. 1 - https://theconversation.com/why-are-some-covid-test-results-false-positives-and-how-common-are-they-162163 https://theconversation.com/why-are-some-covid-test-results-... 2 - https://www.cdc.gov/coronavirus/2019-ncov/cases-updates/previous-testing-in-us.html https://www.cdc.gov/coronavirus/2019-ncov/cases-updates/prev...
- christophilus 5y agoThis, and it’s possible there are real positives where the disease never took. That is, it was detected in the nasal cavity or wherever they’re sampling, but never became an infection that the body had to care about.
- jcelerier 5y agoHow is that compatible with the fact that only 3 or so reported no symptoms ?
- ALittleLight 5y agoMany covid symptoms are also common symptoms of other things (e.g. fatigue, headache, cough). People could legitimately report having covid symptoms while not having covid.
- khuey 5y agoAs it says in their conclusion, you could read the appendix and find out.
- newbamboo 5y agoNobody reads the actual papers it seems. As you point out, for those who don’t read appendices: 3 separate labs ran the pcr tests. And as the paper’s authors rightly point out, they can’t conclude for certain that there were no false positives.
- ouid 5y agoFalse positives for PCR can only plausibly happen through contaminated samples. You should take some time to investigate how PCR works.
- sterlind 5y agofrom what I've read, each round of PCR has a chance of copy errors in a small fraction of the samples. after too many rounds, random noise is generated and amplified. false positives can occur from this noise if the number of rounds is too high, which is why they cap PCR cycles rather than letting it bake forever.
- nradov 5y agoIt's a shame they didn't assay memory T cells in those same subjects. That would have given us a better understanding of their immunity, or lack thereof. There's more to immunity then antibodies. https://www.fda.gov/news-events/press-announcements/coronavirus-covid-19-update-fda-authorizes-adaptive-biotechnologies-t-detect-covid-test https://www.fda.gov/news-events/press-announcements/coronavi...
- nikolay 5y agoIn Bulgaria, they offer a $170 T cell COVID-19 test. I'm surprised you can't get such tests in the States!
- AndrewBissell 5y agoThey are around, but their existence and availability is assiduously kept out of the public discourse. I would bet even a large proportion of primary care physicians don't know about them. Any time the subject of natural immunity comes up you will still very often hear "but the antibodies wane after a few months" as though that is the sole determinant of how well protected a recovered individual is. I will leave the reasons that our public health establishment might want measurement of natural immunity focused on a narrow and rapidly-decaying metric as an exercise for the reader.
- michaelmrose 5y agoNobody is arguing that you can acquire a good degree of immunity by contracting covid and doctors are certainly aware of such tests but there is little import in educating the public about such tests as there is little benefit to the consumer. Even if you have already gotten covid you get better immunity with a very safe vaccination + infection than infection alone and supplies in the states are ample. There simply is no conspiracy because neither the fact nor the motivation makes any sense. I encourage you to think through the matter more thoroughly.
- AndrewBissell 5y ago
- zarzavat 5y agoThis explains why COVID vaccination is capable of treating long COVID in some cases. Hopefully this will lead to some actual treatments for long COVID (for example, a more aggressive regimen of vaccinations), at least the kind of long COVID that results from mild illness.
- techer 5y agoCompletely anecdotally but I had covid in late Feb 2020…no antibodies, brain fog and some chest pain and to my great surprise after the second vaccine two months ago I feel better than I’ve ever felt. I did sleep for 36 hours over that weekend, could be something to do with it.
- mrtksn 5y agoInteresting, which vaccine did you get? Was it one of the mRNA ones?
- techer 5y agoPfizer
- quickthrower2 5y agoHate to say it but it could be the placebo effect.
- 6nf 5y agoHow does the body fight off covid without making antibodies?
- malwarebytess 5y agoDoesn't really track does it? Granted there is much more to an immune response than antibodies alone. To such a degree that an absence of antibodies wouldn't mean there wasn't some immunity present by the rest of the immune system.
- nikolay 5y agoInnate immunity.
- yazaddaruvala 5y agoI really liked this video. I hope it helps. https://youtu.be/lXfEK8G8CUI https://youtu.be/lXfEK8G8CUI
- deleted 5y ago[deleted]
- spikels 5y agoThe innate immune system https://en.wikipedia.org/wiki/Innate_immune_system https://en.wikipedia.org/wiki/Innate_immune_system
- dtech 5y agoThe immune system is very large and complicated, it has lots of ways to deal with infections outside of antibodies.
- f6v 5y agoCD8+ T cells aka killer T cells [0]. 0. https://www.nature.com/articles/d41586-021-00367-7 https://www.nature.com/articles/d41586-021-00367-7
- cheesecake_luvr 5y agoI wonder whether good ol' snot plays a significant role in trapping the virus particles and preventing them from contacting the epithelial cell layers. Maybe that is why snotty children don't seem to get affected.
- poorjohnmacafee 5y agoIIRC this was being discussed when testing first began, that for many their innate immune systems fight off the pathogen so quickly that it doesn't require the adaptive antibody production/retention.
- jansan 5y agoIs it really correct to call people with a positive PCR test who never developed symptoms "patients"?
- yosito 5y agoThat's interesting. Since May I've had symptoms that could be long covid. I did some rapid tests, and nothing ever came back positive. Since then I've been vaccinated with J&J. Did an antibody test two weeks after and nothing showed up. I'm wondering if there is any test I could do at this point to confirm if I've been infected in the past.
- argonaut 5y agoAll the seronegative subjects had a PCR cycle threshold >= 29, with the vast majority above 35, indicating relatively low virus levels. Figure 1, B: https://wwwnc.cdc.gov/eid/article/27/9/21-1042-f1 https://wwwnc.cdc.gov/eid/article/27/9/21-1042-f1
- zmmmmm 5y agothey are sort of hinting at something rather fascinating and I wonder how far I am extrapolating: > Thus, nasopharyngeal viral loads represent a major correlate of the systemic antibody response, whereas age seems to have only a minor effect In other words: you get bad COVID when you inhale it and it infects your airways. But when the primary infection starts elsewhere (eg: bodily fluids) the innate immune system seems to have the upper hand. Imagine if all that frantic hand washing at the beginning of the pandemic was actually counter-productive because infection via fluids is almost like getting a vaccination: a very very mild infection that is rapidly eliminated. Further imagine if kids were partially protected because they mostly gain initial infection through bodily fluids very early on from their parents or other kids. That's a lot of imagining and extrapolating but it's quite fascinating to think about.
- xmprt 5y agoYeah. I'd definitely love to see more research done on this before taking this up but it's an interesting hypothesis.
- bigodbiel 5y agoI can’t help but see the bias in part of the CDC to undermine natural immunity in favor of vaccination as the only viable path. All their publications completely ignore the abundance of recent studies completely disproving their central thesis, always focusing on a narrow, and often problematic, set. Edit: and to add insult to injury the the positive cases were from March-May 2020! My dyslexic mind read ‘21 as would be expected, but no!