10 ms·

For anyone else wondering about the benefits/downsides of the various tests (why do one that takes multiple days when you can do that takes 15 minutes?), the FD

For anyone else wondering about the benefits/downsides of the various tests (why do one that takes multiple days when you can do that takes 15 minutes?), the FDA has a pretty good page on this subject: https://www.fda.gov/consumers/consumer-updates/coronavirus-disease-2019-testing-basics https://www.fda.gov/consumers/consumer-updates/coronavirus-d... The tests that swab your nose or throat and take multiple days are called "molecular" tests and are considered highly accurate. They use controlled heating and cooling cycles to convert the virus' RNA to DNA, which can be detected by specialized lab technique after binding probes to it. Tests like this 15 min one are called "antigen" tests and are still accurate/helpful, but are known to produce more false negatives and false positives compared to molecular.

pmoriarty 6y ago
"Tests like this 15 min one are called "antigen" tests and are still accurate/helpful, but are known to produce more false negatives and false positives compared to molecular." On a large scale, the wrong results from such tests don't matter if you test people often enough (say, every day). If you get a wrong result one day, it'll probably be corrected in the next day or two with more tests. If there was a massive government initiative to manufacture such tests and subsidize them so that everyone got them every day this pandemic could be effectively halted in very short order, even without a vaccine. Almost 6 months ago, the This Week in Virology podcast went in to great detail about this plan, starting at about 6'20" in to episode 640: https://www.microbe.tv/twiv/twiv-640/ https://www.microbe.tv/twiv/twiv-640/ There was also at least one NYT article about it, and it was discussed on HN here: https://news.ycombinator.com/item?id=23878954 https://news.ycombinator.com/item?id=23878954 Unsurprisingly the government did not do this, and we had six more months of deaths instead.
- Analemma_ 6y ago
  > On a large scale, the wrong results from such tests don't matter if you test people often enough (say, every day). But is anyone going to be getting the test every day? Particularly when it apparently costs $30. At that price, once is fine but nobody is going to be doing it over and over; they'll just treat whatever result they get (positive or negative) as binding.
  - pmoriarty 6y ago
    "But is anyone going to be getting the test every day? Particularly when it apparently costs $30." This is why it needs to be subsidized by the government. Also, according to that TWiV episode it could be done for something like $1 per test.
    - justinlink 6y ago
      $330 million per day or nearly 10 billion per month, not counting distribution costs. And could we manufacture 10 billion of them a month?
      - pmoriarty 6y ago
        "could we manufacture 10 billion of them a month?" Yes, it could be done. According to that TWiV episode (which, again, I encourage everyone to listen to) the tests are very simple: just a piece of paper with some antibodies on it. As for the $10 billion per month cost, from the TWiV episode (about 31 minutes in): It just boggles my mind, the enormity of this problem. This is killing enormous numbers of people every day. It's costing the country trillions -- literally trillions of dollars. This should just be part of the national emergency. It's one thing to make vaccines, it's one thing to make therapeutics, but these are things that necessarily take time. We have to wait to see what the efficacy is, we have to... it's really hard to make therapeutics. A diagnostic test should be a no-brainer. Make a $1 test. Get it to everyone. Change the way we view these things, and that should be completely being plowed through by the federal government. We don't have to make 300 million of them overnight. We just have to focus them at the moment in places where the cases are worst... it's just astounding that we don't see a flurry of activity from the US Army... I don't know who makes it, but take every manufacturing company that knows how to print paper, adapt their tools to print monocolonal antibodies on to those sheets and just start slicing it up and shipping it out. It's as easy as that.. well, you know, I'm simplifying it a bit but...
      - lthornberry 6y ago
        $10 billion per month is far, far less than either 1) the economic losses of the pandemic to society, or 2) the amount of money the pandemic is costing the government. I have no knowledge on whether it's feasible, but if it significantly reduced the impact of the pandemic, the economic decision is easy.
- 4ad 6y ago
  > If there was a massive government initiative to manufacture such tests and subsidize them so that everyone got them every day this pandemic could be effectively halted in very short order, even without a vaccine. Absolutely, except that people need to be willing to take the tests. Here in Austria they did a round of free mass testing. The plan was to test the whole population, however only 17% of eligible people showed up. They just don't care. In fact, acquaintances asked me "why did you get tested if you didn't have any symptoms?? don't you have anything better to do with your time?". For the next round of mass testing they are considering paying people €50 just to show up!
  - pmoriarty 6y ago
    "In fact, acquaintances asked me "why did you get tested if you didn't have any symptoms? don't you have anything better to do?"." This is a simple matter of educating the public. The government has done this effectively in, say, wartime, when the importance of acting a certain way (ex. "Loose Lips Sink Ships") is emphasized. You can get nearly everyone on board if the government is competent, on the same side of the issue, and determined. Sadly, in the US we have bickering, incompetent, and ignorant government officials which are often making things worse by ignoring the science or acting directly contrary to it.
    - spion 6y ago
      You need both good leadership and good support. The sense of unity should extend to an actual implementation of unity as well: monetary support for people while they self-isolate would go a long way, for example. Unfortunately I'm afraid that at this point its way too late. The window has moved and the new accepted normal seems to be lots of people dying from the virus. Due to privacy protection those people are also largely invisible to the majority of the population, except for their loved ones - an abstract number. There is also a general sense that "testing doesn't work" - even more so accentuated by the repeated insistence of various medical professionals that rapid tests are "not reliable" (which misses the point - they are not for diagnosis but they're a good infection control tool) and a focus on the vaccines. Success for rapid tests is therefore highly unlikely at this point. Could have worked 3 or 4 months ago. Maybe if there are huge incentives to get tested and a large campaign to inform the public, it could work - but otherwise I doubt it.
- grawprog 6y ago
  >On a large scale, the wrong results from such tests don't matter if you test people often enough (say, every day). If you get a wrong result one day, it'll probably be corrected in the next day or two with more tests. Huh? Continuing to accumulate bad data just leads to a higher accumulation of error. If you have a high percentage of false results and you continue to test over and over the data are still not reliable. How would you know which the correct results are? Say you test 14 days in a row, over those 14 days you've experienced no symptoms, yet 6 tests showed positive and 8 showed negative. Do you have any better idea after those 14 days of testing as to whether you've got covid or not?
  - anon946 6y ago
    Large scale testing is likely aimed at public health, where the goal is to lower Rt < 1. Missing some positives is tolerable. Also, the antigen tests are more sensitive when the person is most likely to be contagious.
  - pmoriarty 6y ago
    It depends on the error rate of the test. If it's close to 50/50 then obviously the test is worthless. But these tests are much more reliable than that, so a population scale the wrong results will be corrected with more testing. I don't have the analysis in front of me, but I encourage you to listen to that TWiV episode yourself and listen to the panel of virologists discussing this. They were initially skeptical also, but after questioning the plan's author they were eventually convinced and became excited because the plan could actually work.
  - vladb38b 6y ago
    With n multiple tests you are much more likely to approach the mean of positive results, which for an actually positive patient is (1-p1)n and for an actually negative patient is p2n, where p1 and p2 are false result probabilities. If p1, p2 << 1 then the means are sufficiently apart that you can compute the probability of getting your result (whatever that is) under the actual positive/negative scenario and one probability will be significantly higher than the other.
    - 6y ago
- deleted 6y ago
  [deleted]
- ineedasername 6y ago
  On a large scale, the wrong results from such tests don't matter if you test people often enough That assumes that for each test it is a sort of dice roll on whether or not there will be a false result. It might be that something about the individual person's biochemistry or health history (like prior exposure to a different corona strain) is the cause of the false result. If that's the case, then people who receive a false result on this type of test will tend to always receive false results, and testing more often won't help much.
  - anon946 6y ago
    If the goal is to lower Rt to below 1, however, it still may be acceptable. See: https://advances.sciencemag.org/content/early/2020/11/20/sciadv.abd5393.1 https://advances.sciencemag.org/content/early/2020/11/20/sci... https://www.medrxiv.org/content/10.1101/2020.06.22.20136309v3 https://www.medrxiv.org/content/10.1101/2020.06.22.20136309v... (preprint of above)
  - spion 6y ago
    Its the viral load, or the amount of virus, mainly. Most people have a large viral load when they are the most infectious, especially in the nose and throat. Testing daily would ensure that you know immediately when you're highly infectious. A recent check of the rapid test used in the UK is that its largely unaware of the virus if the necessary PCR cycles are > 25, gets it right half of the time for CT between 20 and 25 and it gets very good if viral load is large enough to be detected by < 20 cycles. Other rapid tests are AFAIK somewhat better. The main problem that most (western) countries failed to solve is to remove reasons to not take a test and not to self-isolate, and that's primarily inability to get proper support WRT work / monetary situation while self-isolating. Make it easier for people to self-isolate than not to, and people will do it.
  - pas 6y ago
    They can simply use a different test. It'd be much more resource efficient to use the rapid tests on those for whom it works as intended and use PCR (molecular) tests for those who get false positives every time. I have friend who has a colleague who always produces a false pos. antibody test. They know it, they still test him. (At this point basically to make sure the test does something at all.) After all, every kind of proactive/preventive measure helps a bit to keep a group/family/workplace safe.
- SubiculumCode 6y ago
  At $30 per test, I doubt we will get much regular testing with this. Family of four would by $120 per day of testing.
  - spion 6y ago
    Yeah, it should be subsidized so its at least 10 times cheaper. $30 should be a pack of 10 rapid tests. In addition there should be mechanisms to support people who are self-isolating that are sufficient so that its equally easy to self-isolate as it is not to self-isolate
  - pmoriarty 6y ago
    Again, according to that TWiV episode this could be done for $1 per test. And it could be subsidized by the government for those who couldn't afford it.
    - Symmetry 6y ago
      That wouldn't have had the fancy electronics and cell phone app that force the user to show up in government statistics, though. It would just let the user know if they were infectious or not and act accordingly.
      - gojomo 6y ago
        …which would be plenty of info for the primary endpoint of "saving lives". The government's desire for a legible set of stats should take a backseat to the urgent need to inform people how to protect themselves. Let's help people save themselves by not making useful tools illegal. Pretty charts for bureaucracies can wait.
        Symmetry 6y ago
        Yes, ideally that's what would happen. But it's hard for the FDA to approve any new medical device that's worse along a metric the FDA cares about than existing methods. Honestly, the FDA has basically never cared about price and availability before so I'm really surprised they're even letting this one through given that it's less sensitive than a standard PCR. Given how disastrous the FDA's (and CDC's) actions around testing were in February and March I'm relieved things are currently going as well as they are.
- MeinBlutIstBlau 6y ago
  I wouldn't have a problem with the testing at my school if they didn't basically forcefully evict you (and by forcefully, they just threaten you being a student there anymore if you don't leave) or tell you to go into quarantine housing. Which requires you cannot leave your apartment for 14 days. Period no exceptions. And they only give you 4 hours to do it. Even several people moving one person's stuff in 4 hours is absurd. It's like these bureaucrats don't know human psychology. Youre essentially shaming people to a leper colony for a short time just to save face. It wouldn't be so bad if they just told you stay put. But the administration doesn't want to risk seeming incompetent so they heard the sheep in the way that's easiest for them.
- youeseh 6y ago
  > it'll probably be corrected in the next day or two with more tests. Can take 3 tests at the same time to eliminate error, or does the waiting time between repeat tests matter?
  - roywiggins 6y ago
    The test is very good at detecting the virus if you have a high viral load. Waiting a day and doing another test means that the low-level infection you missed yesterday has had another day to replicate, making it easier to detect. You're also probably much more infectious when the virus is at levels that are detectible by the antigen tests, so even if you miss it when it's at a low level, as long as you detect it when you get really infectious it can help lower your chances of transmitting it.
- abfan1127 6y ago
  The US has 330 million people. A weeks worth of testing is 2 billion tests/week. Lets assume they can manufacture 330 million tests a day. Test Costs - $60 billion/week. Shipping Costs - $4-5 billion/week. USPS delivers about 180 million letters a day. Their volume would triple![1] This assumes all of the other problems like 100% participation and zero tech support issues are non-existent. [1] - https://facts.usps.com/one-day https://facts.usps.com/one-day
  - inamberclad 6y ago
    Nah, bundle up tests in 30 day increments. 300 million tests a day becomes 10 million boxes a day. Large, but not impossible.
    - abfan1127 6y ago
      lots of ways to optimize, but the scale is still immense.
      - pmoriarty 6y ago
        We already manufacture and distribute paper products on an immense scale even without it being a national (or global) emergency. Again, according to that TWiV episode, making the tests is not much more complicated than just printing some antibodies on pieces of paper. It could definitely be done, we just need the will to do it. A Manhattan Project for testing could have saved hundreds of thousands of lives and probably trillions of dollars.
        abfan1127 6y ago
        I missed the link to the TWiV episode. do you have it?
        pmoriarty 6y ago
        6'20" in to episode 640: https://www.microbe.tv/twiv/twiv-640/ https://www.microbe.tv/twiv/twiv-640/
- lultimouomo 6y ago
  The governments of Slovakia and of the Bozen province in Italy both organized an antigen testing of their whole population over the course of a weekend (Slovakia did this two times, two weeks apart). From what I can see both attempts were largely unsuccessful in sensibly reducing the spread of Covid, even temporarily. Testing the whole population of Bozen with antigen tests yielded way less positive results than expected, so the feeling was that the tests were just not as sensitive as advertised.
  - ethanbond 6y ago
    I don’t believe this is what GP is referring to. Rather continuously testing people, say 2 times per week, en masse.
  - phobosanomaly 6y ago
    Is it possible that less people were actually infected than was expected?
    - lultimouomo 6y ago
      Possible, but seems unlikely. In Bozen they mass-tested 65% of the population over the course of 3 days. They were getting 540 positive PCR tests every 100k people a week in the week before the mass screening; the latter yielded 900 positive antigen results every 100k people; they got 435 positive PCR tests every 100k people in the week after the screening. This 20% reduction in positive PCR tests seems mostly due to the lockdown, given that the week before the mass screening the reduction had been even greater, 32%.
  - easytiger 6y ago
    The antigen test also seems to be ineffective at detecting igg antibodies months after infection due to their half life and very few non clinically researched focused tests for t or b cells seem to have been carried out anywhere
    - lultimouomo 6y ago
- rhizome 6y ago
  >If there was a massive government initiative to manufacture such tests and subsidize them so that everyone got them every day this pandemic could be effectively halted in very short order, even without a vaccine. Provably false, since over the past 10 months we've seen people all along the way going to parties, restaurants, rallies, airline flights...all after having tested positive. Mooks and celebrities, it hasn't mattered. Your false assumption is that strangers care whether anybody around them dies a painful and lonely death. That's before you even get to the practicality of isolating people who test positive, or to isolate themselves, especially among science disbelievers, Christian congregations, and 2nd Amendment activists.
lbeltrame 6y ago
There's a major difference. Antigen tests identify a protein of the virus, which can be detected only if you have infectious viruses in your respiratory tract. Less sensitive, but highly useful in absence of symptoms, because you know that you need to isolate as you're infectious.
anon946 6y ago
There are also fast molecular tests, using RT-LAMP. https://www.lucirahealth.com/ https://www.lucirahealth.com/ Also when thinking about accuracy, I think it's helpful to distinguish between testing for public health, and testing for medical diagnosis/treatment. Antigen tests tend to be cheaper and have better sensitivity when the person is most likely to be contagious, for example, which, likely make them more suited for public health-oriented frequent, mass-testing.
tzs 6y ago
> The tests that swab your nose or throat and take multiple days are called "molecular" tests and are considered highly accurate ... > Tests like this 15 min one are called "antigen" tests and are still accurate/helpful, but are known to produce more false negatives and false positives compared to molecular. You are correct on "molecular" vs. "antigen" tests in regard to false negatives/positives, but you can't rely on whether or not a test swabs your nose to tell them apart. This newly approved test is indeed an anitgen test, but you collect your sample via nose swab. Here are the accuracy numbers for this new test, in comparison to a laboratory RT-PCR test. This test has a sensitivity of 96% and specificity of 100% for people with COVID symptoms, and 91% sensitivity and 96% specificity for asymptomatic people [1]. Sensitivity is how well a test identifies patients WITH the disease. Specificity is how well a test identifies patients WITHOUT the disease. For completeness, there is a third type of test, an "antibody" test. The molecular tests and the antigen tests try to answer the question "Do I have COVID right now?". The antibody tests try to answer the question "Have I had COVID in the past?". Antibody tests typically involve taking a blood sample. I'm hoping for a cheap, readily available antibody test. I've had enough COVID symptoms at various times over the last few months that it would not surprise me if I had had it, although I probably haven't. I'm overweight and have high blood pressure and approaching retirement age, which on some vaccine distribution plans I've seen would get me fairly early access once the health care and elderly are taken care of. If I've already had COVID, though, I'm fine with waiting until it is generally available to all. An antibody test would help with that decision. [1] https://www.ellumehealth.com/2020/12/10/ellumes-covid-19-home-test-shows-96-accuracy-in-multi-site-us-clinical-study/ https://www.ellumehealth.com/2020/12/10/ellumes-covid-19-hom...
- ilaksh 6y ago
  If you've already had COVID then why would you need a vaccine?
  - tyre 6y ago
    I work for a testing company. We’ve seen patients test positive with months in between.
rplnt 6y ago
> why do one that takes multiple days RNA tests take multiple hours, not days. 4-12 hours is usual, depending on how early in the batch you get swabbed and how often does given place run the tests. Haven't heard about someone waiting more than 24 hours in months, long gone are the problems from spring. If they take days, it's pointing to insufficient testing capacity and/or infrastructure, not to property of the test.
- tyre 6y ago
  Testing is starting to backlog again. We’re the fastest turnaround PCR public testing company and our turnarounds have crept up over 24 hours in the past two weeks. LabCorp and Quest are in the 5–7 day range in some places.

pmoriarty 6y ago

"Tests like this 15 min one are called "antigen" tests and are still accurate/helpful, but are known to produce more false negatives and false positives compared to molecular." On a large scale, the wrong results from such tests don't matter if you test people often enough (say, every day). If you get a wrong result one day, it'll probably be corrected in the next day or two with more tests. If there was a massive government initiative to manufacture such tests and subsidize them so that everyone got them every day this pandemic could be effectively halted in very short order, even without a vaccine. Almost 6 months ago, the This Week in Virology podcast went in to great detail about this plan, starting at about 6'20" in to episode 640: https://www.microbe.tv/twiv/twiv-640/ https://www.microbe.tv/twiv/twiv-640/ There was also at least one NYT article about it, and it was discussed on HN here: https://news.ycombinator.com/item?id=23878954 https://news.ycombinator.com/item?id=23878954 Unsurprisingly the government did not do this, and we had six more months of deaths instead.

Analemma_ 6y ago
> On a large scale, the wrong results from such tests don't matter if you test people often enough (say, every day). But is anyone going to be getting the test every day? Particularly when it apparently costs $30. At that price, once is fine but nobody is going to be doing it over and over; they'll just treat whatever result they get (positive or negative) as binding.
- pmoriarty 6y ago
  "But is anyone going to be getting the test every day? Particularly when it apparently costs $30." This is why it needs to be subsidized by the government. Also, according to that TWiV episode it could be done for something like $1 per test.
  - justinlink 6y ago
    $330 million per day or nearly 10 billion per month, not counting distribution costs. And could we manufacture 10 billion of them a month?
    - pmoriarty 6y ago
      "could we manufacture 10 billion of them a month?" Yes, it could be done. According to that TWiV episode (which, again, I encourage everyone to listen to) the tests are very simple: just a piece of paper with some antibodies on it. As for the $10 billion per month cost, from the TWiV episode (about 31 minutes in): It just boggles my mind, the enormity of this problem. This is killing enormous numbers of people every day. It's costing the country trillions -- literally trillions of dollars. This should just be part of the national emergency. It's one thing to make vaccines, it's one thing to make therapeutics, but these are things that necessarily take time. We have to wait to see what the efficacy is, we have to... it's really hard to make therapeutics. A diagnostic test should be a no-brainer. Make a $1 test. Get it to everyone. Change the way we view these things, and that should be completely being plowed through by the federal government. We don't have to make 300 million of them overnight. We just have to focus them at the moment in places where the cases are worst... it's just astounding that we don't see a flurry of activity from the US Army... I don't know who makes it, but take every manufacturing company that knows how to print paper, adapt their tools to print monocolonal antibodies on to those sheets and just start slicing it up and shipping it out. It's as easy as that.. well, you know, I'm simplifying it a bit but...
    - lthornberry 6y ago
      $10 billion per month is far, far less than either 1) the economic losses of the pandemic to society, or 2) the amount of money the pandemic is costing the government. I have no knowledge on whether it's feasible, but if it significantly reduced the impact of the pandemic, the economic decision is easy.
4ad 6y ago
> If there was a massive government initiative to manufacture such tests and subsidize them so that everyone got them every day this pandemic could be effectively halted in very short order, even without a vaccine. Absolutely, except that people need to be willing to take the tests. Here in Austria they did a round of free mass testing. The plan was to test the whole population, however only 17% of eligible people showed up. They just don't care. In fact, acquaintances asked me "why did you get tested if you didn't have any symptoms?? don't you have anything better to do with your time?". For the next round of mass testing they are considering paying people €50 just to show up!
- pmoriarty 6y ago
  "In fact, acquaintances asked me "why did you get tested if you didn't have any symptoms? don't you have anything better to do?"." This is a simple matter of educating the public. The government has done this effectively in, say, wartime, when the importance of acting a certain way (ex. "Loose Lips Sink Ships") is emphasized. You can get nearly everyone on board if the government is competent, on the same side of the issue, and determined. Sadly, in the US we have bickering, incompetent, and ignorant government officials which are often making things worse by ignoring the science or acting directly contrary to it.
  - spion 6y ago
    You need both good leadership and good support. The sense of unity should extend to an actual implementation of unity as well: monetary support for people while they self-isolate would go a long way, for example. Unfortunately I'm afraid that at this point its way too late. The window has moved and the new accepted normal seems to be lots of people dying from the virus. Due to privacy protection those people are also largely invisible to the majority of the population, except for their loved ones - an abstract number. There is also a general sense that "testing doesn't work" - even more so accentuated by the repeated insistence of various medical professionals that rapid tests are "not reliable" (which misses the point - they are not for diagnosis but they're a good infection control tool) and a focus on the vaccines. Success for rapid tests is therefore highly unlikely at this point. Could have worked 3 or 4 months ago. Maybe if there are huge incentives to get tested and a large campaign to inform the public, it could work - but otherwise I doubt it.
grawprog 6y ago
>On a large scale, the wrong results from such tests don't matter if you test people often enough (say, every day). If you get a wrong result one day, it'll probably be corrected in the next day or two with more tests. Huh? Continuing to accumulate bad data just leads to a higher accumulation of error. If you have a high percentage of false results and you continue to test over and over the data are still not reliable. How would you know which the correct results are? Say you test 14 days in a row, over those 14 days you've experienced no symptoms, yet 6 tests showed positive and 8 showed negative. Do you have any better idea after those 14 days of testing as to whether you've got covid or not?
- anon946 6y ago
  Large scale testing is likely aimed at public health, where the goal is to lower Rt < 1. Missing some positives is tolerable. Also, the antigen tests are more sensitive when the person is most likely to be contagious.
- pmoriarty 6y ago
  It depends on the error rate of the test. If it's close to 50/50 then obviously the test is worthless. But these tests are much more reliable than that, so a population scale the wrong results will be corrected with more testing. I don't have the analysis in front of me, but I encourage you to listen to that TWiV episode yourself and listen to the panel of virologists discussing this. They were initially skeptical also, but after questioning the plan's author they were eventually convinced and became excited because the plan could actually work.
- vladb38b 6y ago
  With n multiple tests you are much more likely to approach the mean of positive results, which for an actually positive patient is (1-p1)n and for an actually negative patient is p2n, where p1 and p2 are false result probabilities. If p1, p2 << 1 then the means are sufficiently apart that you can compute the probability of getting your result (whatever that is) under the actual positive/negative scenario and one probability will be significantly higher than the other.
  - 6y ago
deleted 6y ago
[deleted]
ineedasername 6y ago
On a large scale, the wrong results from such tests don't matter if you test people often enough That assumes that for each test it is a sort of dice roll on whether or not there will be a false result. It might be that something about the individual person's biochemistry or health history (like prior exposure to a different corona strain) is the cause of the false result. If that's the case, then people who receive a false result on this type of test will tend to always receive false results, and testing more often won't help much.
- anon946 6y ago
  If the goal is to lower Rt to below 1, however, it still may be acceptable. See: https://advances.sciencemag.org/content/early/2020/11/20/sciadv.abd5393.1 https://advances.sciencemag.org/content/early/2020/11/20/sci... https://www.medrxiv.org/content/10.1101/2020.06.22.20136309v3 https://www.medrxiv.org/content/10.1101/2020.06.22.20136309v... (preprint of above)
- spion 6y ago
  Its the viral load, or the amount of virus, mainly. Most people have a large viral load when they are the most infectious, especially in the nose and throat. Testing daily would ensure that you know immediately when you're highly infectious. A recent check of the rapid test used in the UK is that its largely unaware of the virus if the necessary PCR cycles are > 25, gets it right half of the time for CT between 20 and 25 and it gets very good if viral load is large enough to be detected by < 20 cycles. Other rapid tests are AFAIK somewhat better. The main problem that most (western) countries failed to solve is to remove reasons to not take a test and not to self-isolate, and that's primarily inability to get proper support WRT work / monetary situation while self-isolating. Make it easier for people to self-isolate than not to, and people will do it.
- pas 6y ago
  They can simply use a different test. It'd be much more resource efficient to use the rapid tests on those for whom it works as intended and use PCR (molecular) tests for those who get false positives every time. I have friend who has a colleague who always produces a false pos. antibody test. They know it, they still test him. (At this point basically to make sure the test does something at all.) After all, every kind of proactive/preventive measure helps a bit to keep a group/family/workplace safe.
SubiculumCode 6y ago
At $30 per test, I doubt we will get much regular testing with this. Family of four would by $120 per day of testing.
- spion 6y ago
  Yeah, it should be subsidized so its at least 10 times cheaper. $30 should be a pack of 10 rapid tests. In addition there should be mechanisms to support people who are self-isolating that are sufficient so that its equally easy to self-isolate as it is not to self-isolate
- pmoriarty 6y ago
  Again, according to that TWiV episode this could be done for $1 per test. And it could be subsidized by the government for those who couldn't afford it.
  - Symmetry 6y ago
    That wouldn't have had the fancy electronics and cell phone app that force the user to show up in government statistics, though. It would just let the user know if they were infectious or not and act accordingly.
    - gojomo 6y ago
      …which would be plenty of info for the primary endpoint of "saving lives". The government's desire for a legible set of stats should take a backseat to the urgent need to inform people how to protect themselves. Let's help people save themselves by not making useful tools illegal. Pretty charts for bureaucracies can wait.
      - Symmetry 6y ago
        Yes, ideally that's what would happen. But it's hard for the FDA to approve any new medical device that's worse along a metric the FDA cares about than existing methods. Honestly, the FDA has basically never cared about price and availability before so I'm really surprised they're even letting this one through given that it's less sensitive than a standard PCR. Given how disastrous the FDA's (and CDC's) actions around testing were in February and March I'm relieved things are currently going as well as they are.
MeinBlutIstBlau 6y ago
I wouldn't have a problem with the testing at my school if they didn't basically forcefully evict you (and by forcefully, they just threaten you being a student there anymore if you don't leave) or tell you to go into quarantine housing. Which requires you cannot leave your apartment for 14 days. Period no exceptions. And they only give you 4 hours to do it. Even several people moving one person's stuff in 4 hours is absurd. It's like these bureaucrats don't know human psychology. Youre essentially shaming people to a leper colony for a short time just to save face. It wouldn't be so bad if they just told you stay put. But the administration doesn't want to risk seeming incompetent so they heard the sheep in the way that's easiest for them.
youeseh 6y ago
> it'll probably be corrected in the next day or two with more tests. Can take 3 tests at the same time to eliminate error, or does the waiting time between repeat tests matter?
- roywiggins 6y ago
  The test is very good at detecting the virus if you have a high viral load. Waiting a day and doing another test means that the low-level infection you missed yesterday has had another day to replicate, making it easier to detect. You're also probably much more infectious when the virus is at levels that are detectible by the antigen tests, so even if you miss it when it's at a low level, as long as you detect it when you get really infectious it can help lower your chances of transmitting it.
abfan1127 6y ago
The US has 330 million people. A weeks worth of testing is 2 billion tests/week. Lets assume they can manufacture 330 million tests a day. Test Costs - $60 billion/week. Shipping Costs - $4-5 billion/week. USPS delivers about 180 million letters a day. Their volume would triple![1] This assumes all of the other problems like 100% participation and zero tech support issues are non-existent. [1] - https://facts.usps.com/one-day https://facts.usps.com/one-day
- inamberclad 6y ago
  Nah, bundle up tests in 30 day increments. 300 million tests a day becomes 10 million boxes a day. Large, but not impossible.
  - abfan1127 6y ago
    lots of ways to optimize, but the scale is still immense.
    - pmoriarty 6y ago
      We already manufacture and distribute paper products on an immense scale even without it being a national (or global) emergency. Again, according to that TWiV episode, making the tests is not much more complicated than just printing some antibodies on pieces of paper. It could definitely be done, we just need the will to do it. A Manhattan Project for testing could have saved hundreds of thousands of lives and probably trillions of dollars.
      - abfan1127 6y ago
        I missed the link to the TWiV episode. do you have it?
        pmoriarty 6y ago
        6'20" in to episode 640: https://www.microbe.tv/twiv/twiv-640/ https://www.microbe.tv/twiv/twiv-640/
lultimouomo 6y ago
The governments of Slovakia and of the Bozen province in Italy both organized an antigen testing of their whole population over the course of a weekend (Slovakia did this two times, two weeks apart). From what I can see both attempts were largely unsuccessful in sensibly reducing the spread of Covid, even temporarily. Testing the whole population of Bozen with antigen tests yielded way less positive results than expected, so the feeling was that the tests were just not as sensitive as advertised.
- ethanbond 6y ago
  I don’t believe this is what GP is referring to. Rather continuously testing people, say 2 times per week, en masse.
- phobosanomaly 6y ago
  Is it possible that less people were actually infected than was expected?
  - lultimouomo 6y ago
    Possible, but seems unlikely. In Bozen they mass-tested 65% of the population over the course of 3 days. They were getting 540 positive PCR tests every 100k people a week in the week before the mass screening; the latter yielded 900 positive antigen results every 100k people; they got 435 positive PCR tests every 100k people in the week after the screening. This 20% reduction in positive PCR tests seems mostly due to the lockdown, given that the week before the mass screening the reduction had been even greater, 32%.
- easytiger 6y ago
  The antigen test also seems to be ineffective at detecting igg antibodies months after infection due to their half life and very few non clinically researched focused tests for t or b cells seem to have been carried out anywhere
  - lultimouomo 6y ago
rhizome 6y ago
>If there was a massive government initiative to manufacture such tests and subsidize them so that everyone got them every day this pandemic could be effectively halted in very short order, even without a vaccine. Provably false, since over the past 10 months we've seen people all along the way going to parties, restaurants, rallies, airline flights...all after having tested positive. Mooks and celebrities, it hasn't mattered. Your false assumption is that strangers care whether anybody around them dies a painful and lonely death. That's before you even get to the practicality of isolating people who test positive, or to isolate themselves, especially among science disbelievers, Christian congregations, and 2nd Amendment activists.

lbeltrame 6y ago

There's a major difference. Antigen tests identify a protein of the virus, which can be detected only if you have infectious viruses in your respiratory tract. Less sensitive, but highly useful in absence of symptoms, because you know that you need to isolate as you're infectious.

anon946 6y ago

There are also fast molecular tests, using RT-LAMP. https://www.lucirahealth.com/ https://www.lucirahealth.com/ Also when thinking about accuracy, I think it's helpful to distinguish between testing for public health, and testing for medical diagnosis/treatment. Antigen tests tend to be cheaper and have better sensitivity when the person is most likely to be contagious, for example, which, likely make them more suited for public health-oriented frequent, mass-testing.

tzs 6y ago

> The tests that swab your nose or throat and take multiple days are called "molecular" tests and are considered highly accurate ... > Tests like this 15 min one are called "antigen" tests and are still accurate/helpful, but are known to produce more false negatives and false positives compared to molecular. You are correct on "molecular" vs. "antigen" tests in regard to false negatives/positives, but you can't rely on whether or not a test swabs your nose to tell them apart. This newly approved test is indeed an anitgen test, but you collect your sample via nose swab. Here are the accuracy numbers for this new test, in comparison to a laboratory RT-PCR test. This test has a sensitivity of 96% and specificity of 100% for people with COVID symptoms, and 91% sensitivity and 96% specificity for asymptomatic people [1]. Sensitivity is how well a test identifies patients WITH the disease. Specificity is how well a test identifies patients WITHOUT the disease. For completeness, there is a third type of test, an "antibody" test. The molecular tests and the antigen tests try to answer the question "Do I have COVID right now?". The antibody tests try to answer the question "Have I had COVID in the past?". Antibody tests typically involve taking a blood sample. I'm hoping for a cheap, readily available antibody test. I've had enough COVID symptoms at various times over the last few months that it would not surprise me if I had had it, although I probably haven't. I'm overweight and have high blood pressure and approaching retirement age, which on some vaccine distribution plans I've seen would get me fairly early access once the health care and elderly are taken care of. If I've already had COVID, though, I'm fine with waiting until it is generally available to all. An antibody test would help with that decision. [1] https://www.ellumehealth.com/2020/12/10/ellumes-covid-19-home-test-shows-96-accuracy-in-multi-site-us-clinical-study/ https://www.ellumehealth.com/2020/12/10/ellumes-covid-19-hom...

ilaksh 6y ago
If you've already had COVID then why would you need a vaccine?
- tyre 6y ago
  I work for a testing company. We’ve seen patients test positive with months in between.

rplnt 6y ago

> why do one that takes multiple days RNA tests take multiple hours, not days. 4-12 hours is usual, depending on how early in the batch you get swabbed and how often does given place run the tests. Haven't heard about someone waiting more than 24 hours in months, long gone are the problems from spring. If they take days, it's pointing to insufficient testing capacity and/or infrastructure, not to property of the test.

tyre 6y ago
Testing is starting to backlog again. We’re the fastest turnaround PCR public testing company and our turnarounds have crept up over 24 hours in the past two weeks. LabCorp and Quest are in the 5–7 day range in some places.