4 ms·

I'm also surprised that there isn't more talk about the sensitivity of the standard nasopharyngeal swab + RT-PCR. When the FDA approved it, they showed it's ex

I'm also surprised that there isn't more talk about the sensitivity of the standard nasopharyngeal swab + RT-PCR. When the FDA approved it, they showed it's extremely accurate... if you use swabs saturated with the virus at various concentrations. Then I read about the poor (70-80%) sensitivity in the real-world, which isn't suprising considering you (1) have variably expert technique in positioning swabs into uncomfortable body spaces, and (2) apply it to people at various stages of the disease with low viral shedding initially and also at end stages. Apparently you can swab two different areas and may raise your sensitivity 10% to 85%. So if you are "negative" with say a 80% sensitivity, that leaves a lot of room for actually infected people to think they are in the clear. There's a reason why screening tests need to be highly accurate. I'm all in favor of at least recognizing the positives and quarantining them, but with a high R0 disease, the false negatives could be a problem.

gitgudnubs 7y ago
If the reproduction rate is 10, and you catch 70% of cases, then the effective reproduction rate will be closer to 3. Since even the highest estimates of the basic reproduction number are only about 4, a test that's 75% accurate means an effective reproduction rate closer to 1. Are you aware of the difference between 4^x and 1^x?
- DocSavage 7y ago
  Since you are being snarky: Are you aware that the sensitivity quoted was mostly in symptomatic and hospitalized patients and not those in the very earliest stages who could also be shedding less virus? Are you aware that each false negative can infect N others, some of whom might have also been previously tested, and also be greenlit to deal with high-risk populations like nursing homes? Are you aware that your 4^x vs 1^x comparison assumes that in that chain everyone is tested, which is not even close to the case now.
  - gitgudnubs 7y ago
    My favorite game. Are you aware that the test can be improved by training medical personnel on sampling technique? Are you aware that tests will, as a general rule, improve? Are you aware that the majority of people understand the difference between 70% and 100% accurate? Are you aware that public policy was affected by poor data on the spread? Are you aware that it's far easier to successfully test [nearly] everyone in the chain when the number of cases is small, like it would have been when this test was initially available? The _only_ way this can be contained is through massive lockdowns. If tests were performed _as soon as possible_, then there's a good chance we could have done a good job containing it through contact tracing. Even if that weren't the case, it would have given our medical system several extra weeks to prepare for the case load. It would have given our politicians better data to enact policies.
    - DocSavage 7y ago
      So after you try to belittle me about not understanding 4^x vs 1^x, you are now talking about future efforts, hopes how an entire medical community can be retrained, etc. Let's stay focused on the real world and not some hypothetical past where we were like South Korea. None of your comments apply to a 1^x spread in the current system since we aren't testing many people, and in hot spots, we aren't testing hardly anyone outside those in hospitals. Here's where we agree. We agree that the only way this can be contained is massive lockdowns, and I believe this particularly true in the face of unreliable and unavailable testing. I also think it has to be coordinated across the country to prevent constant reseeding. We agree that testing everyone would've been good, particularly in the containment phase, but that ship has sailed. My original point is that under the current system where we are occasionally testing the public at large, and also using swab RT-PCR just after suspected infected contact (way before symptoms like Pence, etc), the variable sensitivity is troubling.
      - gitgudnubs 7y ago
        It's like talking to a brick wall. Medical technology is approximately monotonically increasing, so it's absurd to think the test we cobble together in the first month won't be improved upon. The CDC FUCKED UP. I expect careers to be finished. I want a criminal investigation, just in case of corruption, and I hope some people lose their license. But even in the current environment, testing is important. It guides public policy, and it helps doctors triage patients in serious condition. It still helps to limit the spread, and will do so even more when testing overtakes the infection rate (aided by lockdowns). If testing improves, then it could cut weeks off a global lockdown, because the long tail will die that much faster. Not everyone is a neckbeard with a programming job who can live in a basement for two weeks without a single human contact, so anything that helps extinguish this disease helps. Now if you'll excuse me, I should go shave.

gitgudnubs 7y ago

If the reproduction rate is 10, and you catch 70% of cases, then the effective reproduction rate will be closer to 3. Since even the highest estimates of the basic reproduction number are only about 4, a test that's 75% accurate means an effective reproduction rate closer to 1. Are you aware of the difference between 4^x and 1^x?

DocSavage 7y ago
Since you are being snarky: Are you aware that the sensitivity quoted was mostly in symptomatic and hospitalized patients and not those in the very earliest stages who could also be shedding less virus? Are you aware that each false negative can infect N others, some of whom might have also been previously tested, and also be greenlit to deal with high-risk populations like nursing homes? Are you aware that your 4^x vs 1^x comparison assumes that in that chain everyone is tested, which is not even close to the case now.
- gitgudnubs 7y ago
  My favorite game. Are you aware that the test can be improved by training medical personnel on sampling technique? Are you aware that tests will, as a general rule, improve? Are you aware that the majority of people understand the difference between 70% and 100% accurate? Are you aware that public policy was affected by poor data on the spread? Are you aware that it's far easier to successfully test [nearly] everyone in the chain when the number of cases is small, like it would have been when this test was initially available? The _only_ way this can be contained is through massive lockdowns. If tests were performed _as soon as possible_, then there's a good chance we could have done a good job containing it through contact tracing. Even if that weren't the case, it would have given our medical system several extra weeks to prepare for the case load. It would have given our politicians better data to enact policies.
  - DocSavage 7y ago
    So after you try to belittle me about not understanding 4^x vs 1^x, you are now talking about future efforts, hopes how an entire medical community can be retrained, etc. Let's stay focused on the real world and not some hypothetical past where we were like South Korea. None of your comments apply to a 1^x spread in the current system since we aren't testing many people, and in hot spots, we aren't testing hardly anyone outside those in hospitals. Here's where we agree. We agree that the only way this can be contained is massive lockdowns, and I believe this particularly true in the face of unreliable and unavailable testing. I also think it has to be coordinated across the country to prevent constant reseeding. We agree that testing everyone would've been good, particularly in the containment phase, but that ship has sailed. My original point is that under the current system where we are occasionally testing the public at large, and also using swab RT-PCR just after suspected infected contact (way before symptoms like Pence, etc), the variable sensitivity is troubling.
    - gitgudnubs 7y ago
      It's like talking to a brick wall. Medical technology is approximately monotonically increasing, so it's absurd to think the test we cobble together in the first month won't be improved upon. The CDC FUCKED UP. I expect careers to be finished. I want a criminal investigation, just in case of corruption, and I hope some people lose their license. But even in the current environment, testing is important. It guides public policy, and it helps doctors triage patients in serious condition. It still helps to limit the spread, and will do so even more when testing overtakes the infection rate (aided by lockdowns). If testing improves, then it could cut weeks off a global lockdown, because the long tail will die that much faster. Not everyone is a neckbeard with a programming job who can live in a basement for two weeks without a single human contact, so anything that helps extinguish this disease helps. Now if you'll excuse me, I should go shave.