3 ms·

This came up since the beginning in January. The number of people that were reported to reinfect like this seem to lie well within the expected rate of false po

This came up since the beginning in January. The number of people that were reported to reinfect like this seem to lie well within the expected rate of false positives. I don’t understand how this claim is made repeatedly, without a thorough statistical analysis of what is expected.

space_fountain 6y ago
What is the false positive rate for these tests?
yread 6y ago
It's not just tests. All symptoms disappear - we had health workers coming back to hospital and days later symptoms reappeared EDIT: to clarify: in my hospital there were colleagues who tested positive, isolated, had no symptoms, went back to work, still no symptoms. After a few days symptoms are back and they tested positive again
- nil-sec 6y ago
  Could it be that the first test was false positive then and the first symptoms where actually not corona virus?
  - hdjrork 6y ago
    Not if they were tested with PCR. PCR can have false negative, but false positive is extremely unlikely.
    - nil-sec 6y ago
      It’s the other way around. It’s very easy to get a false positive due to DNA contamination.
    - lbeltrame 6y ago
      As someone also said, one of the biggest enemies of PCR is contamination, or perhaps the samples had conservation / handling problems which meant the RNA ended up degraded. Given the (currently) very low numbers of these "apparently relapsed" cases versus the total recovered cases, I think it is most likely.
      - hexl 6y ago
        What about the symptoms?
        lbeltrame 6y ago
        I can think of two ideas on top of my head: - Similar sympthoms but different disease (flu?) - False negatives, and so people were still actually sick In addition, I wonder if those patients had distinct clinical features compared to others. In absence of more data (and these cases are very uncommon) it is hard to tell. Probably a good idea would be to do a study with periodical follow up of a large cohort of discharged patients. This would probably give better indication.
    - pintxo 6y ago
      Globally we are running 100-thousands of tests per week, we must expect to see some false positives under these circumstances.
- radicalbyte 6y ago
  It's flu season, it's quite possible they have had both flu and Coronavirus. My wife had the flu in Feb & early March and the symptoms are identical to the Coronavirus. They're working in a hospital so they'll catch everything.
  - agumonkey 6y ago
    Stupid question does being infected with some virus helps if a second pathogen infects you ? As in 'immune system globally more active' or not at all ?
    - hcknwscommenter 6y ago
      Not a stupid question, but pretty much not at all. In fact, you are slightly immune compromised by the first pathogen against the second pathogen because your adaptive immune system is highly active against the first pathogen. The body has two systems, an innate immune system that has mechanisms to innately attack bacterial and viral pathogens in general and an adaptive immune system that adapts to each specific pathogen. The innate system is a first line of defense but is like a form of combined suicide bomber and cannon fodder throwing cell after cell to overwhelm the pathogen with death and there is significant collateral damage. The adaptive immune system takes time to ramp up to each new pathogen and if it's working on one pathogen doesn't really switch to working on the other. Rather older cells are/have adapted to the first pathogen and newly born cells begin to work on adapting a defense to the new pathogen. This takes time and there are, at the beginning, very few cells adapting to the new pathogen.
robocat 6y ago
There is a video of the head of a hospital in Korea talking about reactivation occurring. I feel that the “false positive” answer is often quickly given, without considering that it is likely that some people that get the virus have it flair up again. Perhaps it is caused by wishful thinking: reactivation is scary so let’s find a less scary reason?
- robocat 6y ago
  Correction as per video at 8 minutes: https://youtu.be/gAk7aX5hksU https://youtu.be/gAk7aX5hksU

space_fountain 6y ago

What is the false positive rate for these tests?

yread 6y ago

It's not just tests. All symptoms disappear - we had health workers coming back to hospital and days later symptoms reappeared EDIT: to clarify: in my hospital there were colleagues who tested positive, isolated, had no symptoms, went back to work, still no symptoms. After a few days symptoms are back and they tested positive again

nil-sec 6y ago
Could it be that the first test was false positive then and the first symptoms where actually not corona virus?
- hdjrork 6y ago
  Not if they were tested with PCR. PCR can have false negative, but false positive is extremely unlikely.
  - nil-sec 6y ago
    It’s the other way around. It’s very easy to get a false positive due to DNA contamination.
  - lbeltrame 6y ago
    As someone also said, one of the biggest enemies of PCR is contamination, or perhaps the samples had conservation / handling problems which meant the RNA ended up degraded. Given the (currently) very low numbers of these "apparently relapsed" cases versus the total recovered cases, I think it is most likely.
    - hexl 6y ago
      What about the symptoms?
      - lbeltrame 6y ago
        I can think of two ideas on top of my head: - Similar sympthoms but different disease (flu?) - False negatives, and so people were still actually sick In addition, I wonder if those patients had distinct clinical features compared to others. In absence of more data (and these cases are very uncommon) it is hard to tell. Probably a good idea would be to do a study with periodical follow up of a large cohort of discharged patients. This would probably give better indication.
  - pintxo 6y ago
    Globally we are running 100-thousands of tests per week, we must expect to see some false positives under these circumstances.
radicalbyte 6y ago
It's flu season, it's quite possible they have had both flu and Coronavirus. My wife had the flu in Feb & early March and the symptoms are identical to the Coronavirus. They're working in a hospital so they'll catch everything.
- agumonkey 6y ago
  Stupid question does being infected with some virus helps if a second pathogen infects you ? As in 'immune system globally more active' or not at all ?
  - hcknwscommenter 6y ago
    Not a stupid question, but pretty much not at all. In fact, you are slightly immune compromised by the first pathogen against the second pathogen because your adaptive immune system is highly active against the first pathogen. The body has two systems, an innate immune system that has mechanisms to innately attack bacterial and viral pathogens in general and an adaptive immune system that adapts to each specific pathogen. The innate system is a first line of defense but is like a form of combined suicide bomber and cannon fodder throwing cell after cell to overwhelm the pathogen with death and there is significant collateral damage. The adaptive immune system takes time to ramp up to each new pathogen and if it's working on one pathogen doesn't really switch to working on the other. Rather older cells are/have adapted to the first pathogen and newly born cells begin to work on adapting a defense to the new pathogen. This takes time and there are, at the beginning, very few cells adapting to the new pathogen.

robocat 6y ago

There is a video of the head of a hospital in Korea talking about reactivation occurring. I feel that the “false positive” answer is often quickly given, without considering that it is likely that some people that get the virus have it flair up again. Perhaps it is caused by wishful thinking: reactivation is scary so let’s find a less scary reason?

robocat 6y ago
Correction as per video at 8 minutes: https://youtu.be/gAk7aX5hksU https://youtu.be/gAk7aX5hksU