4 ms·

Probably the false-positive rate of antibody tests would be a big problem as long as only a small fraction of the population is infected. From what I've read, t

by fsh 7y ago

Probably the false-positive rate of antibody tests would be a big problem as long as only a small fraction of the population is infected. From what I've read, the specificity of such tests is way worse than for RNA-based tests.

ImaCake 7y ago
Last I checked they had a roughly 10% false positive rate. So if 1 in 1000 people were infected but you tested all 1000 with an antibody assay, you would get 100 positives, and probably one of them is actually infected. Basically useless for mass screening. The gold standard RT-PCR assay has basically zero false positives, but requires experienced personnel and expensive reagents to do en-mass.
- foobarian 7y ago
  I keep seeing news articles along the lines of "People getting reinfected" "In 5% of cases recovered patients tested positive for COVID-10 2 months later" "Asymptomatic individuals test positive for COVID anyway" Yeah very mysterious indeed :)
  - rjsw 7y ago
    Why would you think that people couldn't get reinfected ? The virus won't just bounce off your skin after one has got into you. If it is present everywhere in the environment then you will keep getting infected, maybe faster than your immune system can deal with it. The end point to aim for in terms of immunity is that your immune system can deal with any level of viral load in the future without you becoming ill. Maybe combined with prophylactic drugs that help prevent the virus reproducing as fast within you.
- vikramkr 7y ago
  But we wouldn't pick up any of the people who are now immune right?
  - ImaCake 7y ago
    The RTPCR will only work for those with viral RNA in them. So those with active infections. The antibody test won't work until the host produces antibodies against the virus (except for false positives). So yeah, the antibody test will detect those who are immune, or at least have antibodies against Covid-19 whereas the RT-PCR will not.
- tullatulla 7y ago
  Pharmact lateral flow test had zero false positives among 126 negative samples as far as I can see: https://www.nature.com/articles/d41587-020-00010-2 https://www.nature.com/articles/d41587-020-00010-2 https://pharmact.eu/ https://pharmact.eu/ Don't know if this would show immunity though.
  - ImaCake 7y ago
    >100% Konformitatsrate (Spezifitatsrate) fur 126 Negativkontrollen mit nicht mit SARS-CoV-2 akut oder vorher infizierten Probanden. Heh, well that's great news. It's an antibody test so it would tell you who has had antibodies against the virus and thus who is probably immune to it.

by fsh 7y ago

ImaCake 7y ago

Last I checked they had a roughly 10% false positive rate. So if 1 in 1000 people were infected but you tested all 1000 with an antibody assay, you would get 100 positives, and probably one of them is actually infected. Basically useless for mass screening. The gold standard RT-PCR assay has basically zero false positives, but requires experienced personnel and expensive reagents to do en-mass.

foobarian 7y ago
I keep seeing news articles along the lines of "People getting reinfected" "In 5% of cases recovered patients tested positive for COVID-10 2 months later" "Asymptomatic individuals test positive for COVID anyway" Yeah very mysterious indeed :)
- rjsw 7y ago
  Why would you think that people couldn't get reinfected ? The virus won't just bounce off your skin after one has got into you. If it is present everywhere in the environment then you will keep getting infected, maybe faster than your immune system can deal with it. The end point to aim for in terms of immunity is that your immune system can deal with any level of viral load in the future without you becoming ill. Maybe combined with prophylactic drugs that help prevent the virus reproducing as fast within you.
vikramkr 7y ago
But we wouldn't pick up any of the people who are now immune right?
- ImaCake 7y ago
  The RTPCR will only work for those with viral RNA in them. So those with active infections. The antibody test won't work until the host produces antibodies against the virus (except for false positives). So yeah, the antibody test will detect those who are immune, or at least have antibodies against Covid-19 whereas the RT-PCR will not.
tullatulla 7y ago
Pharmact lateral flow test had zero false positives among 126 negative samples as far as I can see: https://www.nature.com/articles/d41587-020-00010-2 https://www.nature.com/articles/d41587-020-00010-2 https://pharmact.eu/ https://pharmact.eu/ Don't know if this would show immunity though.
- ImaCake 7y ago
  >100% Konformitatsrate (Spezifitatsrate) fur 126 Negativkontrollen mit nicht mit SARS-CoV-2 akut oder vorher infizierten Probanden. Heh, well that's great news. It's an antibody test so it would tell you who has had antibodies against the virus and thus who is probably immune to it.