We’re Testing the Wrong People • Hacker News Board

Re: We’re Testing the Wrong People

#31

Post by jcranmer » Thu, Apr 23, 2020, 4:38 PM UTC

votepaunchy wrote: post #19

ryanobjc wrote: post #9

Since many states cannot deficit spend, the strategy of 'leaving it to the states' is a deliberate strategy of abdicating responsibility at the federal executive level. With a federal unitary executive disinterested in expanding testing, and no other backstop, we are left without a country-wide strategy. I'm thinking that we won't get out from under this shroud until we get a new president.

The only thing stopping states from deficit spending (selling bonds to pay for general obligations) are the states’ own rules. As we have seen, constitutional requirements are not an impediment in a pandemic.

Which constitutional requirements do you think are being violated? And if you're going to say first amendment, be sure to explain precisely why they wouldn't survive strict scrutiny. (And if you're not aware of the legal meaning of "strict scrutiny," then you are probably ignorant of what the Constitution has actually been held to mean by the authority that has the power to interpret it.)

Re: We’re Testing the Wrong People

#32

Post by munificent » Thu, Apr 23, 2020, 4:39 PM UTC

> Another promising pathway is to pool many tests and run them together. If a pooled sample tests negative, everyone in the pool is negative. If it is positive, the members of the pool can be tested individually.

Well, it took a global pandemic, but we finally found a use for bloom filters!

Re: We’re Testing the Wrong People

#33

Post by joshuamorton » Thu, Apr 23, 2020, 4:41 PM UTC

munificent wrote: post #32

> Another promising pathway is to pool many tests and run them together. If a pooled sample tests negative, everyone in the pool is negative. If it is positive, the members of the pool can be tested individually. Well, it took a global pandemic, but we finally found a use for bloom filters!

This is not a new thing in medical testing. They do it for donated blood already.

Re: We’re Testing the Wrong People

#34

Post by awinter-py » Thu, Apr 23, 2020, 4:48 PM UTC

sampling bias debate reminds me of this stats legend from ww2:

the USAF wanted to armor planes where the bullet holes were. statistician abe wald recommended armoring where the bullet holes weren't on the theory that those were the non-survivable hits

can't interpret a statistic until you think about what's excluded from the sample

Re: We’re Testing the Wrong People

#35

Post by exhilaration » Thu, Apr 23, 2020, 4:48 PM UTC

RandallBrown wrote: post #25

I've been saying this since the beginning of this whole thing. I don't understand why we haven't focused all of our testing on people that aren't sick so we can catch the asymptomatic cases that are out in the world spreading it to everyone.

Because we don't have enough tests. We could reopen the country if we could test enough people, but we're stuck. Even in New York and New Jersey, tests are still limited to symptomatic people because there isn't enough testing capacity.

Re: We’re Testing the Wrong People

#36

Post by LolWolf » Thu, Apr 23, 2020, 4:50 PM UTC

munificent wrote: post #32

> Another promising pathway is to pool many tests and run them together. If a pooled sample tests negative, everyone in the pool is negative. If it is positive, the members of the pool can be tested individually. Well, it took a global pandemic, but we finally found a use for bloom filters!

This idea is called group testing [0] and has been used by the army for quite a while. It is also a well-studied problem in information theory as a (useful) basic model and we know optimal solutions to it.

What is surprising is that group testing tells us that we can actually do better: the specific construction you pinpoint the people who come up positive, without needing to have a test for each person [1] and this result is optimal in the expected number of tests. I'm surprised that most labs haven't already been doing this (but I would suspect some have).

Wootters has wonderful notes on the mathematical background for this—I really recommend them. [2]

-----

[0] https://en.wikipedia.org/wiki/Group_testing

[1] Of course, we require an upper bound on the total prevalence, but even a weak upper bound yields fairly good savings in testing.

[2] Page 3 on of http://web.stanford.edu/~marykw/classes/CS250_W18/lectureNot...

Re: We’re Testing the Wrong People

#37

Post by _Anken » Thu, Apr 23, 2020, 4:51 PM UTC

gumby wrote: post #12

alex_young wrote: post #3

The only data that is somewhat reliable in this pandemic is COVID deaths. Testing the population that is very sick / dying is crucial to understanding the baseline for the worst part of the problem. Once you have that under control, and we are not nearly there yet, you have to get every first responder tested regularly so you can prevent them from spreading the disease and give them some assurance that coming to work…

> The only data that is somewhat reliable in this pandemic is COVID deaths. I agree,, especially as you included the word “somewhat”. We have pretty good numbers on people who died in hospitals, but people who died at home appear to be seriously under counted. Additionally, consequential deaths are currently invisible. These are people who died, say, ecause the coronavirus crowded out their access to hospitals. There…

Most nursing home deaths are not getting tested either.

Re: We’re Testing the Wrong People

#38

Post by empath75 » Thu, Apr 23, 2020, 4:51 PM UTC

lokar wrote: post #4

This seems to ignore the importance of testing symptomatic people to rule out COVID (the most common outcome) so care givers can stop wasting PPE (which is is short supply).

During a pandemic, it's more likely than not that any negative test on a symptomatic person is false.

It's also quite likely that a positive test on an asymptomatic person is also false -- depending on how prevalent it is in the general population.

Re: We’re Testing the Wrong People

#39

Post by beamatronic » Thu, Apr 23, 2020, 4:56 PM UTC

RandallBrown wrote: post #25

I've been saying this since the beginning of this whole thing. I don't understand why we haven't focused all of our testing on people that aren't sick so we can catch the asymptomatic cases that are out in the world spreading it to everyone.

Keep in mind, we've learned so much. At the beginning there were some authorities (China, WHO) claiming there was no human-to-human transmission. It's too bad they would have ever made that statement, because I think people latched onto that and didn't let go of the idea.

Re: We’re Testing the Wrong People

#40

Post by pmoriarty » Thu, Apr 23, 2020, 4:58 PM UTC

This was covered about a month ago in episode 595 of This Week in Virology[1], in answer to a listener question:

Rich Condit: Garrett writes: The CDC guidelines are to test hospitalized patients and symptomatic health care workers first, and the symptomatic general public last. This seems backwards to me.

Alan Dove: Yeah. I just had this conversation with my wife after she had some, I mentioned this before, she had some coughing and shortness of breath, got immediately sent to the ER in the hospital where she works, and they did a chest x-ray, it was clear, and they said, "Ok, you don't meet criteria for testing. Go back to work." And she's been fine since then, and she, we were talking about it and she said, "Well, isn't that exactly who they should test, because then I could go and infect patients?" and I said, "Well, if they had enough tests, yes. But if you expand the testing to the people who are less sick, you don't have enough tests. Whereas if you restrict the testing to the people who are sickest, you do have enough tests." So it's a.. it's not the right way to do it, but it's the way that you actually can do it.

Vincent Racaniello: Yeah, we're in this position because we don't have enough tests. We didn't ramp up...

Dove: Because we don't have enough tests. We didn't prepare fast enough.

Racaniello: If we had, we could test a lot of people and get an idea of how many actual infections there were, which would be very useful. But... we can't. So we're stuck with this current policy.

[1]- http://www.microbe.tv/twiv/twiv-595/ about 1 hour and 19 minutes in to the program