6 ms·

Duh, they only detect levels of viral load sufficient to make a person infectious, around 1e6 RNA copies per cc of fluid. And viral load tends to peak somewher

Duh, they only detect levels of viral load sufficient to make a person infectious, around 1e6 RNA copies per cc of fluid. And viral load tends to peak somewhere in the 1e10 to 1e14 range, people at 1e6 really have to work at coughing directly on to growth plates to create a sample. Back in the early days of Covid-19 people didn't typically begin displaying symptoms visible without an x-ray until they'd nearly reach their peak viral load. More recently people tend to start displaying symptoms earlier. This is probably due to the adaptive immune system learning about covid through immunization or prior infection, but could also be something related to Omicron variants becoming dominant. But in any event, it takes a while to get the results back from a test more sensitive than a rapid test. If you take a rapid test and send off a sample for PCR every hour then you'll collect a positive PCR sample long before you collect a positive rapid antigen sample. But you might very well get the results from the rapid test first since viral loads tend to increase rapidly in the early stages and can cross the ~4 orders of magnitude in the time it takes to turn around a PCR test. EDIT: Actually, I should say and those peak viral loads I quoted are from 2020 when I was paying the most attention to this stuff and have likely changed with mass vaccination/prior infection and Omicron.

BoxFour 3y ago
Indeed, it appears that this is somewhat redundant. A majority, if not all, of the rapid tests I have used explicitly caution against taking one in the absence of symptoms, as it is expected to yield negligible results.
- tinco 3y ago
  I got stuck in the United States, was not allowed to fly back home until I got a negative result on a rapid test. It still took a week to test negative after I'd been symptom free.
  - BoxFour 3y ago
    Regrettably, there are individuals who exhibit evident symptoms yet would gladly travel and deceive on a simple questionnaire. That might explain why governments adopt a blanket rapid test approach irrespective of the potential for false positives (even given the potential, as the article alludes to, for false negatives).
    - mullingitover 3y ago
      This fact is evidence for my hypothesis that humans are engineered by viruses as a means of transportation.
      - NoZebra120vClip 3y ago
        In the same manner that humans have been domesticated by wheat, with all the best land, food, water, and cushiest existence on the planet. (I believe that this was a comment by Niven or Heinlein.)
    - jrmg 3y ago
      You’re now expected just to mask up and travel. Recently just had this experience with a family member. Airline would not do anything at all. Travel agent (website) would only book a new flight, but not refund the old one - they said (probably truthfully) that the airline ties their hands. Travel insurance would only pay out if the trip was _cut short_ because of a COVID diagnosis (how does that even work?), or if they were placed under mandatory quarantine by a government authority. Seems unethical to me on all fronts but that’s how things are. I suppose it’s not much different to how people are now, in most countries, just expected to go to work unless they’re heavily symptomatic (and even the “unless they’re heavily symptomatic” seems like lip-service that is not universally observed).
      - jrmg 3y ago
        Actually, maybe I should amend that. “You’re now expected just to mask up and travel” is really “You’re now expected just to travel”. The considerate may mask up of their own volition - no one is enforcing it, and there are barely any recommendations.
  - dboreham 3y ago
    14 days here
  - belltaco 3y ago
    Were you a citizen or permanent resident of the country you call home? As far as I know almost no countries put restrictions on their own citizens from returning. Some had quarantine requirements.
    - talldatethrow 3y ago
      Their country might have let them in if they showed up at the border/customs.... But they weren't allowed on a commercial plane flight probably.
    - tinco 3y ago
      No restrictions, but they offered no way of getting home either. My colleague had the same problem when she wanted to visit her dying grandfather in Japan. They weren't letting sick people in even if they did manage to get on a flight. For me the problem was mostly the flight.
- harha 3y ago
  And yet they made it in policies all around the world with lots of people involved poking around in the other peoples noses and throats.
  - basisword 3y ago
    I’ve never seen a rapid test done by anyone other than the person taking the test. And most now only require a small nose swab rather than nose and throat. In fact any PCR tests I did were also self-administered (with guidance) so that the patient didn’t accidentally cough/sneeze on the nurse.
    - harha 3y ago
      In many European and Asian countries this was the prerequisite to get approval from the app to not be locked up
  - gjulianm 3y ago
    Precisely the point of most of those policies was to use rapid tests to ensure you weren't being infections at that moment or close to it. I honestly don't know what's so controversial about them.
    - harha 3y ago
      I can figure out for myself if I have symptoms or not
      - Broken_Hippo 3y ago
        So? That's not the point. You and I both know that not everyone will be upfront about symptoms. The tests are there to attempt to cut down on this.
      - maxbond 3y ago
        Sometimes in society, we adopt laws that are about keeping other people safe more than they are about keeping yourself comfortable. You might feel inconvenienced. Ultimately, you're the beneficiary of this too. Your life is going to be a lot longer, because the people around you are occasionally inconvenienced for your benefit. If this isn't acceptable to you, I'm sorry about that, that's tough.
deleted 3y ago
[deleted]
u654th8jt 3y ago
> Duh, they only detect levels of viral load sufficient to make a person infectious, Then how do you explain this: > However, repeating the test 3 times, 48 hours apart, led to detection of infections in 75% of asymptomatic participants.
- black6 3y ago
  False positives.
  - headsupernova 3y ago
    These are exceedingly rare, like almost never happen.
    - mike_hearn 3y ago
      That's unfortunately not the case. PCR false positives are a massive problem. Scientists liked to claim during COVID that PCR tests don't have false positive because they use an obscure definition that doesn't match how people normally use the term. I wrote about this problem back in 2020 when it started becoming apparent that the public health establishment wasn't attempting to stop or even measure COVID PCR test false positives, because they had simply defined the problem out of existence [1]. Yet dig into the literature a bit and you discover that FPs are a well known problem that have occurred many times before. There are at least three problems and arguably more: 1. Scope limits. Scientists have an extremely myopic view of what counts as an FP somewhat akin to "that's not a bug it's a feature" in the software world. Sample contaminated somewhere along the line from collection to machine? Maybe even when the sample brushed up against the outside of the machine itself, or the skin of a lab worker? Not a false positive in their view, because the PCR test itself is finding the RNA fragment it's looking for. PCR detects virus your immune system already destroyed? Not a false positive, because the test is actually looking for RNA so begins with a lysis stage that breaks open the viral capsid anyway. Results got mixed up in a shoddy IT system? Not a false positive because the "test" is just the machine they operate, not the whole infrastructure the public interacts with. 2. Over-sensitivity. COVID PCR tests were run at thresholds normally considered way too sensitive for normal usage, which is why they were so frequently triggering for weeks after a patient seemed to have fully recovered. Even with CTs ~25 these tests were pre-2020 run in extremely controlled labs with specialized air handling equipment and the like, to try and avoid FPs, but COVID tests were being routinely run in ad-hoc labs with CTs of over 40 and each additional cycle is twice as sensitive as the last! 3. Circular logic. Normally medicine is careful to keep pathogen and disease separate. It's important because some diseases ("collections of symptoms") can be caused by multiple pathogens, or no pathogen, and many people become infected with a pathogen yet never develop disease. In the very early days of COVID the distinction between disease and causative agent was kept properly separated because diagnosis was done by doctors, but this didn't survive contact with the public health establishment. They wanted a mass-scale system in the incorrect belief that they could slow down spread this way (there's no link in the data between testing levels and outcomes). Once mass PCR testing started the definition of COVID became circular: A positive test means you have COVID, but COVID was defined as having a positive test. It's obvious what happens if you define COVID this way: the tests can by definition never have false positives. On what basis can you dispute the accuracy of the test if the test and not disease is defined to be ground truth? Using this approach, false positives always become "asymptomatic cases" that inconveniently never become sick and thus are not a case under classical medical reasoning. This is what led to bizarre claims coming from health authorities, like the claim that the tests had FP rates of zero. But it's not reality. As I document in the essay, we know PCR results have FPs because there have been "pseudo-epidemics" in the past where ordinary coughs and colds were mis-diagnosed as outbreaks of dangerous diseases due to bad PCR results, and because lab challenges have often returned failures i.e. labs were submitted samples known to contain just ordinary rhinovirus or whatever and came back with positive SARS-CoV-2 results. There were also cases where reagent mixups caused false results, or where PCR tests returned results that switched between negative and positive then back to negative from samples taken back to back and so on. None of these were ever really investigated or root caused. And all that's before you get into the systems that surround the labs. I got a PCR certificate for someone else's name at one point, almost certainly a form autofill mistake (I saw workers wrestling with this problem when they lost my wife's results). When I complained I got a new certificate in under 5 minutes for my own name this time but now the results were signed off by a different doctor i.e. the signatures supposedly demonstrating expert supervision of the test were just being randomly picked by software. [1] https://blog.plan99.net/pseudo-epidemics-7603b2da839 https://blog.plan99.net/pseudo-epidemics-7603b2da839

BoxFour 3y ago

Indeed, it appears that this is somewhat redundant. A majority, if not all, of the rapid tests I have used explicitly caution against taking one in the absence of symptoms, as it is expected to yield negligible results.

tinco 3y ago
I got stuck in the United States, was not allowed to fly back home until I got a negative result on a rapid test. It still took a week to test negative after I'd been symptom free.
- BoxFour 3y ago
  Regrettably, there are individuals who exhibit evident symptoms yet would gladly travel and deceive on a simple questionnaire. That might explain why governments adopt a blanket rapid test approach irrespective of the potential for false positives (even given the potential, as the article alludes to, for false negatives).
  - mullingitover 3y ago
    This fact is evidence for my hypothesis that humans are engineered by viruses as a means of transportation.
    - NoZebra120vClip 3y ago
      In the same manner that humans have been domesticated by wheat, with all the best land, food, water, and cushiest existence on the planet. (I believe that this was a comment by Niven or Heinlein.)
  - jrmg 3y ago
    You’re now expected just to mask up and travel. Recently just had this experience with a family member. Airline would not do anything at all. Travel agent (website) would only book a new flight, but not refund the old one - they said (probably truthfully) that the airline ties their hands. Travel insurance would only pay out if the trip was _cut short_ because of a COVID diagnosis (how does that even work?), or if they were placed under mandatory quarantine by a government authority. Seems unethical to me on all fronts but that’s how things are. I suppose it’s not much different to how people are now, in most countries, just expected to go to work unless they’re heavily symptomatic (and even the “unless they’re heavily symptomatic” seems like lip-service that is not universally observed).
    - jrmg 3y ago
      Actually, maybe I should amend that. “You’re now expected just to mask up and travel” is really “You’re now expected just to travel”. The considerate may mask up of their own volition - no one is enforcing it, and there are barely any recommendations.
- dboreham 3y ago
  14 days here
- belltaco 3y ago
  Were you a citizen or permanent resident of the country you call home? As far as I know almost no countries put restrictions on their own citizens from returning. Some had quarantine requirements.
  - talldatethrow 3y ago
    Their country might have let them in if they showed up at the border/customs.... But they weren't allowed on a commercial plane flight probably.
  - tinco 3y ago
    No restrictions, but they offered no way of getting home either. My colleague had the same problem when she wanted to visit her dying grandfather in Japan. They weren't letting sick people in even if they did manage to get on a flight. For me the problem was mostly the flight.
harha 3y ago
And yet they made it in policies all around the world with lots of people involved poking around in the other peoples noses and throats.
- basisword 3y ago
  I’ve never seen a rapid test done by anyone other than the person taking the test. And most now only require a small nose swab rather than nose and throat. In fact any PCR tests I did were also self-administered (with guidance) so that the patient didn’t accidentally cough/sneeze on the nurse.
  - harha 3y ago
    In many European and Asian countries this was the prerequisite to get approval from the app to not be locked up
- gjulianm 3y ago
  Precisely the point of most of those policies was to use rapid tests to ensure you weren't being infections at that moment or close to it. I honestly don't know what's so controversial about them.
  - harha 3y ago
    I can figure out for myself if I have symptoms or not
    - Broken_Hippo 3y ago
      So? That's not the point. You and I both know that not everyone will be upfront about symptoms. The tests are there to attempt to cut down on this.
    - maxbond 3y ago
      Sometimes in society, we adopt laws that are about keeping other people safe more than they are about keeping yourself comfortable. You might feel inconvenienced. Ultimately, you're the beneficiary of this too. Your life is going to be a lot longer, because the people around you are occasionally inconvenienced for your benefit. If this isn't acceptable to you, I'm sorry about that, that's tough.

deleted 3y ago

[deleted]

u654th8jt 3y ago

> Duh, they only detect levels of viral load sufficient to make a person infectious, Then how do you explain this: > However, repeating the test 3 times, 48 hours apart, led to detection of infections in 75% of asymptomatic participants.

black6 3y ago
False positives.
- headsupernova 3y ago
  These are exceedingly rare, like almost never happen.
  - mike_hearn 3y ago
    That's unfortunately not the case. PCR false positives are a massive problem. Scientists liked to claim during COVID that PCR tests don't have false positive because they use an obscure definition that doesn't match how people normally use the term. I wrote about this problem back in 2020 when it started becoming apparent that the public health establishment wasn't attempting to stop or even measure COVID PCR test false positives, because they had simply defined the problem out of existence [1]. Yet dig into the literature a bit and you discover that FPs are a well known problem that have occurred many times before. There are at least three problems and arguably more: 1. Scope limits. Scientists have an extremely myopic view of what counts as an FP somewhat akin to "that's not a bug it's a feature" in the software world. Sample contaminated somewhere along the line from collection to machine? Maybe even when the sample brushed up against the outside of the machine itself, or the skin of a lab worker? Not a false positive in their view, because the PCR test itself is finding the RNA fragment it's looking for. PCR detects virus your immune system already destroyed? Not a false positive, because the test is actually looking for RNA so begins with a lysis stage that breaks open the viral capsid anyway. Results got mixed up in a shoddy IT system? Not a false positive because the "test" is just the machine they operate, not the whole infrastructure the public interacts with. 2. Over-sensitivity. COVID PCR tests were run at thresholds normally considered way too sensitive for normal usage, which is why they were so frequently triggering for weeks after a patient seemed to have fully recovered. Even with CTs ~25 these tests were pre-2020 run in extremely controlled labs with specialized air handling equipment and the like, to try and avoid FPs, but COVID tests were being routinely run in ad-hoc labs with CTs of over 40 and each additional cycle is twice as sensitive as the last! 3. Circular logic. Normally medicine is careful to keep pathogen and disease separate. It's important because some diseases ("collections of symptoms") can be caused by multiple pathogens, or no pathogen, and many people become infected with a pathogen yet never develop disease. In the very early days of COVID the distinction between disease and causative agent was kept properly separated because diagnosis was done by doctors, but this didn't survive contact with the public health establishment. They wanted a mass-scale system in the incorrect belief that they could slow down spread this way (there's no link in the data between testing levels and outcomes). Once mass PCR testing started the definition of COVID became circular: A positive test means you have COVID, but COVID was defined as having a positive test. It's obvious what happens if you define COVID this way: the tests can by definition never have false positives. On what basis can you dispute the accuracy of the test if the test and not disease is defined to be ground truth? Using this approach, false positives always become "asymptomatic cases" that inconveniently never become sick and thus are not a case under classical medical reasoning. This is what led to bizarre claims coming from health authorities, like the claim that the tests had FP rates of zero. But it's not reality. As I document in the essay, we know PCR results have FPs because there have been "pseudo-epidemics" in the past where ordinary coughs and colds were mis-diagnosed as outbreaks of dangerous diseases due to bad PCR results, and because lab challenges have often returned failures i.e. labs were submitted samples known to contain just ordinary rhinovirus or whatever and came back with positive SARS-CoV-2 results. There were also cases where reagent mixups caused false results, or where PCR tests returned results that switched between negative and positive then back to negative from samples taken back to back and so on. None of these were ever really investigated or root caused. And all that's before you get into the systems that surround the labs. I got a PCR certificate for someone else's name at one point, almost certainly a form autofill mistake (I saw workers wrestling with this problem when they lost my wife's results). When I complained I got a new certificate in under 5 minutes for my own name this time but now the results were signed off by a different doctor i.e. the signatures supposedly demonstrating expert supervision of the test were just being randomly picked by software. [1] https://blog.plan99.net/pseudo-epidemics-7603b2da839 https://blog.plan99.net/pseudo-epidemics-7603b2da839