4 ms·

Let me give you a counter example. A friend of mine is only 25 years old and fit (resting heart rate below 70). They got infected with Covid twice within 2 mont

Let me give you a counter example. A friend of mine is only 25 years old and fit (resting heart rate below 70). They got infected with Covid twice within 2 months. They tested positive on a PCR test. The second infection was significantly worse and they are constantly out of breath and struggling with pneumonia. Do not underestimate this disease. Especially the new Indian variant. Having antibodies is not necessarily the same as being protected. Especially in the light of variants and the fact that antibodies can wane over time.

skocznymroczny 5y ago
PCR tests are not a reliable method to determine infection. Is it possible that your friend had a pneumonia and it just shows on the test?
- hef19898 5y ago
  Why wouldn't PCR tests be a reliable test for infection?
  - skocznymroczny 5y ago
    Google "PCR false positive" "PCR false negative" for some sources. Also, there's the whole cycle issue, by changing the number of cycles, you can switch between a pandemic and endemic situation almost at will.
    - hef19898 5y ago
      Every test has false positives and false negatives. From pregnancy tests to HIV tests. Doesn't mean the test is unreliable, does it? No idea what your second point is supposed to be about.
      - atatatat 5y ago
        Depends on your standard for reliable.
  - Pyramus 5y ago
    Not parent, but there has been a popular alternative facts campaign that aims to discredit PCR tests, partially on misunderstanding how PCR tests work (e.g. ct values, false positives etc.) and partially on technicalities that PCR tests show the existence of virus DNA, which in theory could also be present without the host developing an infection. Google Corman-Drosten review if you want to go down this rabbit hole, it's both fascinating and horrifying to see the state of the art of pseudo-science.
    - hef19898 5y ago
      I wasn't sure if it was that, I had my doubts so. What I saw from that "discussion" so far is enough for me to stay as far away from it as possible.
  - nradov 5y ago
    A PCR test indicates the presence of viral genetic material but that isn't sufficient to diagnose an active infection. A patient who has recovered from infection can continue to test positive for an extended period, especially if a high number of cycles are used.
    - hef19898 5y ago
      I would assume the number of cycles is pre-determined. Not that I checked, so. But again, how is that a bad thing? You check for the virus by looking fo viral DNA. Good, you found it in suffcient numbers to conclude the person is infected. Solid approach. A lot of stuff is checked for indirectly. Reading too much into that just shows an incredible degree of ignorance.
      - nradov 5y ago
        The number of cycles can be configured on the test machines. That number is pre-determined for each particular test protocol. The presence of viral DNA doesn't necessarily indicate the presence of an active infection or live virus that can spread to others. This isn't good or bad, it's just how the test works.
        hef19898 5y ago
        Pretty much what I thought then. And each result should then have a confidence interval attached to it that the result "patient infected" is correct. Also, distinguishing between "viral DNA present" and "virus present" seems like a lot of nitpicking to me. You can't have the one without the other.
        nradov 5y ago
        You're really missing the point. There is no way to calculate a confidence interval for the presence of an active infection based solely on a PCR test. That is a yes or no judgment call made by a clinician based on multiple objective and subjective factors. Recovered patients often continue to test positive even long after the infection has cleared and they are no longer infected. Thus a PCR test on it's own isn't a reliable way to detect re-infection. https://www.uptodate.com/contents/covid-19-diagnosis https://www.uptodate.com/contents/covid-19-diagnosis
  - egberts1 5y ago
    PCR test when cycled toward a certain number just to gain accuracy yet loses its accuracy when cycled too much: PCR can only detect active infection. Some COVID PCR tests have fairly bothersome false positive and false negative percentage (enough to make its own statistic to be that 3rd axiom (of lies, damn lies, and …): it’s the bane of shifty government policies that is being based on this type of test, PCR. Antibody test detects past and current infection through T-cell memory of past encounters and that too is limited by how long the “learned” imprint of the virus can last (as short as 6-month by some “peer-reviewed” papers on COVID antibody memory. I would be most pressed to see what this aspect of duration of COVID-related T-cell memory turn out to be (but these data are sparse and not quite available to most of us). Antibody is the costlier test of two (also not being more used toward formulation of government policies as I think they should be). Whereas, Smallpox, DTP and polio vaccine memory have established their multi-decade reliability.
vixen99 5y ago
As you say, antibodies != protection necessarily. And asymptomatic people don't have antibodies from the start though they do after infection albeit without symptoms. They do have T-cells which offer protection in these cases. But the status of one's immune system is critical so adopting advice in this department is paramount.
pokstad 5y ago
That’s really sad about your friend, but you’re using one anecdotal case to scare people about covid. Young fit people have died from the flu before. If we’re going to make big decisions, they need to be rational ones based on data, not emotional pleas from individuals.
- atatatat 5y ago
  This, still?
  - chaostheory 5y ago
    I can understand this earlier in the pandemic, but don't we have enough data now to not be overly reliant on personal anecdotes?

skocznymroczny 5y ago

PCR tests are not a reliable method to determine infection. Is it possible that your friend had a pneumonia and it just shows on the test?

hef19898 5y ago
Why wouldn't PCR tests be a reliable test for infection?
- skocznymroczny 5y ago
  Google "PCR false positive" "PCR false negative" for some sources. Also, there's the whole cycle issue, by changing the number of cycles, you can switch between a pandemic and endemic situation almost at will.
  - hef19898 5y ago
    Every test has false positives and false negatives. From pregnancy tests to HIV tests. Doesn't mean the test is unreliable, does it? No idea what your second point is supposed to be about.
    - atatatat 5y ago
      Depends on your standard for reliable.
- Pyramus 5y ago
  Not parent, but there has been a popular alternative facts campaign that aims to discredit PCR tests, partially on misunderstanding how PCR tests work (e.g. ct values, false positives etc.) and partially on technicalities that PCR tests show the existence of virus DNA, which in theory could also be present without the host developing an infection. Google Corman-Drosten review if you want to go down this rabbit hole, it's both fascinating and horrifying to see the state of the art of pseudo-science.
  - hef19898 5y ago
    I wasn't sure if it was that, I had my doubts so. What I saw from that "discussion" so far is enough for me to stay as far away from it as possible.
- nradov 5y ago
  A PCR test indicates the presence of viral genetic material but that isn't sufficient to diagnose an active infection. A patient who has recovered from infection can continue to test positive for an extended period, especially if a high number of cycles are used.
  - hef19898 5y ago
    I would assume the number of cycles is pre-determined. Not that I checked, so. But again, how is that a bad thing? You check for the virus by looking fo viral DNA. Good, you found it in suffcient numbers to conclude the person is infected. Solid approach. A lot of stuff is checked for indirectly. Reading too much into that just shows an incredible degree of ignorance.
    - nradov 5y ago
      The number of cycles can be configured on the test machines. That number is pre-determined for each particular test protocol. The presence of viral DNA doesn't necessarily indicate the presence of an active infection or live virus that can spread to others. This isn't good or bad, it's just how the test works.
      - hef19898 5y ago
        Pretty much what I thought then. And each result should then have a confidence interval attached to it that the result "patient infected" is correct. Also, distinguishing between "viral DNA present" and "virus present" seems like a lot of nitpicking to me. You can't have the one without the other.
        nradov 5y ago
        You're really missing the point. There is no way to calculate a confidence interval for the presence of an active infection based solely on a PCR test. That is a yes or no judgment call made by a clinician based on multiple objective and subjective factors. Recovered patients often continue to test positive even long after the infection has cleared and they are no longer infected. Thus a PCR test on it's own isn't a reliable way to detect re-infection. https://www.uptodate.com/contents/covid-19-diagnosis https://www.uptodate.com/contents/covid-19-diagnosis
- egberts1 5y ago
  PCR test when cycled toward a certain number just to gain accuracy yet loses its accuracy when cycled too much: PCR can only detect active infection. Some COVID PCR tests have fairly bothersome false positive and false negative percentage (enough to make its own statistic to be that 3rd axiom (of lies, damn lies, and …): it’s the bane of shifty government policies that is being based on this type of test, PCR. Antibody test detects past and current infection through T-cell memory of past encounters and that too is limited by how long the “learned” imprint of the virus can last (as short as 6-month by some “peer-reviewed” papers on COVID antibody memory. I would be most pressed to see what this aspect of duration of COVID-related T-cell memory turn out to be (but these data are sparse and not quite available to most of us). Antibody is the costlier test of two (also not being more used toward formulation of government policies as I think they should be). Whereas, Smallpox, DTP and polio vaccine memory have established their multi-decade reliability.

vixen99 5y ago

As you say, antibodies != protection necessarily. And asymptomatic people don't have antibodies from the start though they do after infection albeit without symptoms. They do have T-cells which offer protection in these cases. But the status of one's immune system is critical so adopting advice in this department is paramount.

pokstad 5y ago

That’s really sad about your friend, but you’re using one anecdotal case to scare people about covid. Young fit people have died from the flu before. If we’re going to make big decisions, they need to be rational ones based on data, not emotional pleas from individuals.

atatatat 5y ago
This, still?
- chaostheory 5y ago
  I can understand this earlier in the pandemic, but don't we have enough data now to not be overly reliant on personal anecdotes?