Guest cherzeca Posted April 21, 2020 Posted April 21, 2020 "If we test in a high prevalence setting, it is more likely that persons who test positive truly have disease than if the test is performed in a population with low prevalence.." this is supposed to be meaningful...?
Dalal.Holdings Posted April 21, 2020 Posted April 21, 2020 More info: https://online.stat.psu.edu/stat507/node/71/ Nah, that requires math, not just common sense. So it must be wrong. ;D Nice job, I Lol'd.
orthopa Posted April 21, 2020 Posted April 21, 2020 For those that feel strongly we should track and trace how would you go about that? I'm not arguing against it but the man power needed, the time for testing, and the tracking really would border on unfathomable. How often do you test someone? If they have a fever at home? At work? Whats a fever? I have patients that tell me they "run low" and 99 degrees is a fever for them. Once a week for everyone in a hot spot or cluster? How do you coordinate a couple hundred thousand people that may have taken public transit, etc and find the time let alone the resources to actually see these people in a medical facility, test them, and then trace even outside of immediate family/workplace. You quickly could be over a million contacts in a week. Its mind boggling and virtually impossible. I think in theory its great and those seeing patients/clients in any business would quickly understand the many power/time/facility/cost to event try to test 5000 people in a couple days let alone trace contacts ON TOP providing healthcare for the public once the States re opn. Who is going to do this? As bad as it sounds practically speaking herd immunity/vaccine/cure is only option. I fear a testing/tracking program would fail miserably. Not because its not the right thing to do or best thing to do but I feel it would border on downright impossible in a country like the US. I give the S. Koreans a lot credit if this was the true reason it worked. God damn.
Spekulatius Posted April 21, 2020 Posted April 21, 2020 For those that feel strongly we should track and trace how would you go about that? I'm not arguing against it but the man power needed, the time for testing, and the tracking really would border on unfathomable. How often do you test someone? If they have a fever at home? At work? Whats a fever? I have patients that tell me they "run low" and 99 degrees is a fever for them. Once a week for everyone in a hot spot or cluster? How do you coordinate a couple hundred thousand people that may have taken public transit, etc and find the time let alone the resources to actually see these people in a medical facility, test them, and then trace even outside of immediate family/workplace. You quickly could be over a million contacts in a week. Its mind boggling and virtually impossible. I think in theory its great and those seeing patients/clients in any business would quickly understand the many power/time/facility/cost to event try to test 5000 people in a couple days let alone trace contacts ON TOP providing healthcare for the public once the States re opn. Who is going to do this? As bad as it sounds practically speaking herd immunity/vaccine/cure is only option. I fear a testing/tracking program would fail miserably. Not because its not the right thing to do or best thing to do but I feel it would border on downright impossible in a country like the US. I give the S. Koreans a lot credit if this was the true reason it worked. God damn. Contact tracing only works well when you have a small number of cases. When you exceed about 100 cases, it can‘t be done comprehensively and then the only way to works this is to prioritize the contacts (work, family, vulnerable persons who came in contact etc) and hopefully get them quickly quarantined and tested (with rapid feedback). I know for fact that it’s done in Germany and I think they are trying in Massachusetts.
tng Posted April 21, 2020 Posted April 21, 2020 For those that feel strongly we should track and trace how would you go about that? I'm not arguing against it but the man power needed, the time for testing, and the tracking really would border on unfathomable. How often do you test someone? If they have a fever at home? At work? Whats a fever? I have patients that tell me they "run low" and 99 degrees is a fever for them. Once a week for everyone in a hot spot or cluster? How do you coordinate a couple hundred thousand people that may have taken public transit, etc and find the time let alone the resources to actually see these people in a medical facility, test them, and then trace even outside of immediate family/workplace. You quickly could be over a million contacts in a week. Its mind boggling and virtually impossible. I think in theory its great and those seeing patients/clients in any business would quickly understand the many power/time/facility/cost to event try to test 5000 people in a couple days let alone trace contacts ON TOP providing healthcare for the public once the States re opn. Who is going to do this? As bad as it sounds practically speaking herd immunity/vaccine/cure is only option. I fear a testing/tracking program would fail miserably. Not because its not the right thing to do or best thing to do but I feel it would border on downright impossible in a country like the US. I give the S. Koreans a lot credit if this was the true reason it worked. God damn. Yeah, once you look at the false positive rate and false negative rate of existing tests, and then look at how many people use the subway system in New York and Boston, you have to become very skeptical that it will work. How many false positives are going to be in one train alone (let alone the dozens of trains during rush hour)? You'll end up tracing down the entirety of the city on false positives alone. And if you let a single false negative into a system that transports millions of people a day, you are fucked. The thing that sucks is that tests for this virus are not very accurate. That's why I think that the actual reason why South Korea isn't hit as hard are actually due to far more simpler reasons, such as face masks or low obesity rate.
RichardGibbons Posted April 21, 2020 Posted April 21, 2020 This has some nice quotes from COVID-19: https://thebeaverton.com/2020/04/we-need-to-open-up-the-economy-and-get-back-to-work-says-covid-19/
SHDL Posted April 21, 2020 Posted April 21, 2020 Oh boy: https://twitter.com/realDonaldTrump/status/1252418369170501639?s=20
samwise Posted April 21, 2020 Posted April 21, 2020 https://peterattiamd.com/covid-19-whats-wrong-with-the-models/ Thanks for the interesting links Liberty. He now believes that true infections are way higher and true mortality way lower than he thought a month ago. He is suggesting that an anti-body test in NYC is now needed to know the true infections rate. If we truly find large numbers were infected, way above the false positive rate, that would be good news for health and wealth. Not sure what he saw to change his mind. But assuming the death rate is much lower, what would change? Not sure it would change anything about the correct policy response. No government will want their ICUs overloaded. So they will reduce contacts every time ICUs seem to be getting full, and ease up when ICUs are way below capacity. The virus reacts fast. So they will get constant feedback in 10-14 days. What it would change is reduced ultimate deaths and the less time before we get to normal. Less time means companies and consumers will burn through less cash, or take on less debt. These are good for equity investors.
Viking Posted April 21, 2020 Posted April 21, 2020 Oh boy: https://twitter.com/realDonaldTrump/status/1252418369170501639?s=20 Trump is getting killed on how he has managed the virus and it is getting worse. So what does he do? He manufactures a new ‘issue’ that the news media will shift their focus to. The messier the better. Smart, smart man! However, this is not good for the US. Among other things, immigration brings in needed skills. It also provides a nice boost to GDP as all those immigrants provide a nice economic boost (need to eat and sleep somewhere).
SHDL Posted April 21, 2020 Posted April 21, 2020 Oh boy: https://twitter.com/realDonaldTrump/status/1252418369170501639?s=20 Trump is getting killed on how he has managed the virus and it is getting worse. So what does he do? He manufactures a new ‘issue’ that the news media will shift their focus to. The messier the better. Smart, smart man! However, this is not good for the US. Among other things, immigration brings in needed skills. It also provides a nice boost to GDP as all those immigrants provide a nice economic boost (need to eat and sleep somewhere). Yes this is not good. I am very worried about where this is going.
Cigarbutt Posted April 21, 2020 Posted April 21, 2020 ^Assessing the size of the invisible part of the iceberg is important. The California serology studies are interesting and need to be taken into account. However, if the validity of results is reduced by the same methodological flaws (selection bias, specificity bias underestimation {a specificity of 98% vs 99% can have a major effect on results} and extrapolation risk), results may be precise (values similar and pointing in the same direction) but also precisely wrong (not accurate). I think Mr. Maboussin discusses this noise-versus-signal issue for investments. See below for the tests used (if i understood correctly) and look at specificity. There have been issues with tests rapidly going to the markets in this environment. https://imgcdn.mckesson.com/CumulusWeb/Click_and_learn/Premier_Biotech_COVID19_Package_Insert.pdf An interesting aspect and a way to build power of knowledge for the future would indeed be to use a similar (to California studies) methodology to highly affected areas. Applying the same approach to the NYC area or NY state, one would expect (by + or - similar extrapolation) about a 50% positive rate of seroconversion in the general population. This would also help to put a price tag on the strategy based on reaching natural immunity. It is a well known fact that Scandinavian countries have developed expertise for long-term longitudinal studies. One of the reasons (beside talent and experience) is that the populations are considered to be relatively captive. It seems that the US just decided to increase the degree of captivity in a protectionist way. Slippery slope.
Jurgis Posted April 21, 2020 Posted April 21, 2020 Oh boy: https://twitter.com/realDonaldTrump/status/1252418369170501639?s=20 Poor Melania. It was nice to know her.
rb Posted April 21, 2020 Posted April 21, 2020 Oh boy: https://twitter.com/realDonaldTrump/status/1252418369170501639?s=20 Trump is getting killed on how he has managed the virus and it is getting worse. So what does he do? He manufactures a new ‘issue’ that the news media will shift their focus to. The messier the better. Smart, smart man! However, this is not good for the US. Among other things, immigration brings in needed skills. It also provides a nice boost to GDP as all those immigrants provide a nice economic boost (need to eat and sleep somewhere). Yes this is not good. I am very worried about where this is going. Is anybody thinking about what happens with vegetables from California, Georgia and all these places? Or we're all just gonna have to shift to eating corn?
Jurgis Posted April 21, 2020 Posted April 21, 2020 Oh boy: https://twitter.com/realDonaldTrump/status/1252418369170501639?s=20 Trump is getting killed on how he has managed the virus and it is getting worse. So what does he do? He manufactures a new ‘issue’ that the news media will shift their focus to. The messier the better. Smart, smart man! However, this is not good for the US. Among other things, immigration brings in needed skills. It also provides a nice boost to GDP as all those immigrants provide a nice economic boost (need to eat and sleep somewhere). Yes this is not good. I am very worried about where this is going. Is anybody thinking about what happens with vegetables from California, Georgia and all these places? Or we're all just gonna have to shift to eating corn? I am sure the great value investors from CoBF will finally get jobs picking strawberries. Your all hard work is going to be sincerely appreciated.
Liberty Posted April 21, 2020 Posted April 21, 2020 https://www.cnn.com/2020/04/20/opinions/trump-institutions-autocrats-kasparov/index.html Gary Kasparov op-ed.
LongHaul Posted April 21, 2020 Posted April 21, 2020 https://www.cnn.com/2020/04/20/opinions/trump-institutions-autocrats-kasparov/index.html Gary Kasparov op-ed. Great article. No matter your politics in the US - the last thing we all want is a dictator who slowly or quickly strips away our freedom. All Hail Dictator Trump also known as Mr. Deficit.
DooDiligence Posted April 21, 2020 Posted April 21, 2020 https://www.cnn.com/2020/04/20/opinions/trump-institutions-autocrats-kasparov/index.html Gary Kasparov op-ed. Great article. No matter your politics in the US - the last thing we all want is a dictator who slowly or quickly strips away our freedom. All Hail Dictator Trump also known as Mr. Deficit. That's Comrade Trump, AKA Mr. Bankruptcy. Anyone want to guess as to when he'll throw out the possibility of defaulting / renegotiating US debt (again)?
Liberty Posted April 21, 2020 Posted April 21, 2020 Central quarantine away from family is more of a unifying feature of effective Asian responses to the coronavirus than widespread testing (Taiwan = very little testing relatively speaking). For what it’s worth, I think central quarantine of positive cases (a good use for hotels!) is more obviously useful for limiting spread than masks (which I also support). Lots of spread happens at home. Also: Doctors should be aware most serology tests haven't been reviewed by FDA. Quality is highly variable, with some or perhaps many giving uncertain results. False positive rates may be inappropriately high. Patients and doctors shouldn't rely on unproven tests for clinical decisions Depending on specificity of serology test being used, false positive rates can range from 25-50%; meaning tests that return positive result saying you have antibodies to covid may be wrong as much as half the time. Many tests have 95% specificity which leaves false positives high
ERICOPOLY Posted April 21, 2020 Posted April 21, 2020 They are protesting the guidelines that Trump himself put into place and later extended to April 30th.
ERICOPOLY Posted April 21, 2020 Posted April 21, 2020 Trump sees partisan scheme in calls for ramped up virus testing To hear Trump tell it, the focus on coronavirus testing is a partisan scheme to "get him." That's demonstrably ridiculous. https://www.msnbc.com/rachel-maddow-show/trump-sees-partisan-scheme-calls-ramped-virus-testing-n1188751 Trump believes criticisms of him can't be sincere, so they must be part of a plot. He peddled a related line at yesterday's press briefing: "Remember it was all ventilators and the reason it was all ventilators, 'They said there's no way he'll ever be able to catch this one.' And not only did we catch it, we are now the king of ventilators all over the world. We can send them anywhere; we have thousands being made a week and they are very high quality. And that wasn't playing well, so then they said, Testing, testing, oh we'll get him on testing.'" There is no partisan scheme. As CNN's Daniel Dale explained, "The Republican governors of Ohio, Nebraska, Maryland and Massachusetts, Republican Senate health committee Chairman Sen. Lamar Alexander and other Republicans have all spoken in the last week about challenges obtaining testing materials or the need for more testing.... This is about more than Trump's unfortunate paranoia. If the president genuinely believes calls for ramped up testing are little more than a plot to "get him," he may be less likely to take the policy prescription seriously. For the public's sake, Trump needs to understand that this is not a plot; it's a real piece of the puzzle he's eager to solve.
Viking Posted April 21, 2020 Posted April 21, 2020 For those that feel strongly we should track and trace how would you go about that? I'm not arguing against it but the man power needed, the time for testing, and the tracking really would border on unfathomable. I think what you are really asking is this: is it important. And if so how important? The US decided it was important to go to the moon. With leadership, planning, experts, resources, money and effort they made it happen. Yes, there were set backs; learn, iterate and keep going. The virus is killing the global economy (not just the US). And it is costing lives. I think one can make the case that this is the biggest economic/health issue to hit the globe since the great depression. So i think we can all agree that dealing with the ‘virus’ is massively important. So it then follows that governments would do everything in their power to deal with it. One would expect the government to mobilize all necessary resources no different than when it fought WW1, WW2 or when it decided to go to the moon. And the leadership HAS to come at the national level. It also needs massive international coordination. Imaging fighting WW1 or WW2 without international coordination? Or how about if the US presidents at the time said ‘we are going to fight a world war and the states individually can manage the the war effort as they chose as per the loose guidelines as set forth by the Federal government.’ And then the President then said that all people who do not support the war should let their governors know and actively demonstrate in their state. And the states were also short on ammunition; production of which was controlled by the government who said when they asked for more ‘you have enough...’ Some countries have decided that dealing with the virus is of the utmost importance: Taiwan and South Korea. It has taken great political leadership, a national approach, has required individuals to give up some personal freedoms. Most importantly it required a vision, planning, trust in science, excellent communication, resource mobilization (people and medical), cooperation, strong execution. Is it important? If so, how important?
cobafdek Posted April 21, 2020 Posted April 21, 2020 ^Assessing the size of the invisible part of the iceberg is important. The California serology studies are interesting and need to be taken into account. However, if the validity of results is reduced by the same methodological flaws (selection bias, specificity bias underestimation {a specificity of 98% vs 99% can have a major effect on results} and extrapolation risk), results may be precise (values similar and pointing in the same direction) but also precisely wrong (not accurate). I think Mr. Maboussin discusses this noise-versus-signal issue for investments. See below for the tests used (if i understood correctly) and look at specificity. There have been issues with tests rapidly going to the markets in this environment. https://imgcdn.mckesson.com/CumulusWeb/Click_and_learn/Premier_Biotech_COVID19_Package_Insert.pdf The manufacturers of that test report specificities of 99.2% for the IgM and 99.5% for the IgG, which sound excellent. But these are based on validating their tests by "Clinical Diagnosis/Confirmed," which presumably means symptomatic cases confirmed with a +RT-PCR. So that's the selection bias. It might be useful in a hospital setting. But when survey testing a larger and different population (asymptomatic or mildly symptomatic), they will get more false positives, which means lower specificity. It's interesting their package insert admits this much at the very end: "Some cross reactivity was observed with samples positive for SARS-CoV antibody and Rheumatoid Factor. It is possible to cross-react with samples positive for MERS-CoV antibody. Positive results may be due to past or present infection with non-SARS-CoV-2 coronavirus strains, such as coronavirus HKU1, NL63, OC43, or 229E." But they present no data on how large this cross-reactivity is. If large, specificity might be much lower. So it's probably not useful for community-wide testing for contact tracing, where a positive test will need to be confirmed by the RT-PCR.* I fear a testing/tracking program would fail miserably. Not because its not the right thing to do or best thing to do but I feel it would border on downright impossible in a country like the US. *One way it may be possible: Abbott's ID NOW COVID-19 test (a PCR test), according to my hospital which is about to deploy it (and according to Abbott - if they can be believed) has a very low false positive rate. It could therefore be used to confirm a positive serological test that has an unacceptably large false positivity. Abbott's rapid test, however, would have to be more widely available outside the hospital setting. The McKesson test could still be useful for epidemiological purposes. Epidemiological models could use a range of false positive numbers to adjust their past models in order get better estimates of CFR and IFR. I'm still waiting for Mt. Sinai's serological (ELISA) test (brought up in this thread last month https://www.medrxiv.org/content/10.1101/2020.03.17.20037713v2). I think they test for antibodies to different Covid-19 proteins. They claim no cross-reactivity to other non-Covid19 coronaviruses. I give the S. Koreans a lot credit if this was the true reason it worked. God damn. I bet the South Korean tests will be revealed also to have poor performance characteristics. So that a large factor for the relative success in that population was psychological. When they see a lot a weird "scientific" testing being done, combined with all that highly publicized spraying of the sidewalks/streets/buildings with whatever homeopathic fluid by men in hazmat suits, it's great propaganda to enforce quarantining.
Liberty Posted April 21, 2020 Posted April 21, 2020 They are protesting the guidelines that Trump himself put into place and later extended to April 30th. He doesn't care about coherence, just about whatever could advantage him. By politicizing this, he's creating the conditions to blame others, whatever happens. As Kasparov wrote here: It also appears Trump is using crucial medical supplies and federal small business aid for political purposes. He is inciting a culture war that sounds almost like a civil war with unhinged tweets about "liberating" states under lockdown -- only ones with Democratic governors, of course. https://www.cnn.com/2020/04/20/opinions/trump-institutions-autocrats-kasparov/index.html
Dalal.Holdings Posted April 21, 2020 Posted April 21, 2020 He doesn't care about coherence, just about whatever could advantage him. By politicizing this, he's creating the conditions to blame others, whatever happens. As Kasparov wrote here: It also appears Trump is using crucial medical supplies and federal small business aid for political purposes. He is inciting a culture war that sounds almost like a civil war with unhinged tweets about "liberating" states under lockdown -- only ones with Democratic governors, of course. https://www.cnn.com/2020/04/20/opinions/trump-institutions-autocrats-kasparov/index.html Pretty much the exact opposite of what you’d want from a President in a crisis like this. SMH.
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