Monday, September 21, 2020

Jacobin pandemic

Casey Mulligan tweeted an interesting report on the coronavirus from Jacobin online magazine as "makes the most sense." Given that the Jacobins were 

"the most radical and ruthless of the political groups formed in the wake of the French Revolution, and in association with Robespierre they instituted the Terror of 1793–4."

(google dictionary) the link attracted my eye. (Do these people know history? Or is this intentional? And they're all upset about Trump and "authoritarianism?")  

Indeed, after the predictable throat-clearing editorializing about "disparate impact" and inequality, and despite idiotic question preambles like this one

"Under capitalism, we have become a species that increasingly exploits other creatures and their habitats, and moves in large numbers and with great speed around the globe, making us ripe for a pandemic like this one."

(China is.. capitalist? The plague, cholera, yellow fever, smallpox were... what?) Jacobin editorial board member Nicole Aschoff spurs Harvard professors Katherine Yih  and Martin Kulldorff to interesting, sensible and useful answers. The extreme source of this commonsense gives me some hope. However, read though or skip to my critical comments, as it's not as totally wise as Casey suggests. 

KY: ... I don’t think it’s wise or warranted to keep society locked down until vaccines become available. ..Instead of a medically oriented approach that focuses on the individual patient and seeks (unrealistically) to prevent new infections across the board, we need a public health–oriented approach that focuses on the population  and seeks to use patterns, or epidemiologic features, of the disease to minimize the number of cases of severe disease and death over the long run, as herd immunity builds up.

NA: Like Dr Yih, I am very concerned about the collateral damage of lockdowns. In public health policy, we cannot just consider the present consequences of one single disease. We must think more broadly, considering all short- and long-term health outcomes.

...Another example is school closings. Good education is not only important for academic achievement and financial well-being; it is also critical for the mental and physical health of children and into their subsequent adulthood. Kids have minimal risk from this virus, and it is sad that we are sacrificing our children instead of properly protecting the elderly and other high-risk groups.

(I hate to break it to modern-day Jacobins, but the Trump Administration is basically following this approach. And the disparate impact is precisely brought on by economic lockdown.  ) 

Read on for much common sense. 

However, I don't think this is totally right, and "damn the torpedoes, protect the old folks and let's sail on to herd immunity" is not, I think the right or at least complete answer.  

1) Herd immunity, on its own, is a meaningless concept.  Most people think herd immunity happens when everyone has gotten it, which is false.  A virus stops spreading when the reproduction rate is below one. The reproduction rate combines frequency of contact and fraction of immune in the population. Only that combination matters.

If each infected person meets 3 people and 67% of the population has immunity, the virus stops.  If each infected person meets two people and 51% the population has immunity, the virus stops. If each infected person meets 0.99 people and nobody is immune, the virus stops.  The fraction with immunity on its own is meaningless.

So we need to work on both parts of the equation -- reduce the contact rate and minimum economic and social cost, as well as wait for greater numbers to become immune. 

2) Long term consequences.  The article acknowledges these and moves on. This strikes me as a great unknown. The view that it’s like the flu, just let people get it until immunity rises, while keeping old and sick people safe, is predicated on the idea that there are few long term consequences other than death. 

 If 20% are getting long term important debilitation, that skews the treadeoff to less contact.  If this were the plague or cholera, with 50% death, we would not be talking about herd immunity.

3) Testing. The article is missing the one great opportunity we have to reduce the spread and reduce the social and economic cost of the disease, until a vaccine becomes available. "Test" only appears in the article in the section on protecting the elderly and nursing homes. This is the great unexploited opportunity. We can cheaply reduce the contact rate with next to no business or social cost.

Why in the world are we not embarking on widespread public-health testing? Why is the FDA still regulating tests, saying they may only be performed in a medical setting?  By what possible right or common sense can the FDA tell me that I cannot send samples of my body to a lab, and the lab cannot tell me what’s in them? Read Alex Tabarrok "our antigens, ourselves" to get really grumpy about this. You have to be astoundingly paternalistic about the stupid deplorable to believe that people need to be protected from simple information about what is in their body. There is zero medical danger from a saliva test. 

This thing could be over in  weeks if the FDA allowed cheap, fast, relatively inaccurate, cash-and-carry, completely unregulated tests. Go to CVS, get the test kit, find out if you have it. No referral, no doctor visit, no prescription, no insurance, no faxed paperwork. Let private decisions figure out what to do with the results. Businesses, restaurants, schools could all demand it. With a cheap test, the contact rate can go below one and we need no immunity. Of course, the government has every interest in paying for and subsidizing tests too. 

Frankly I do not understand this Administration. If President Trump simply tweeted, "FDA: Free the tests!" and "CDC: tell people to get tested" this thing could be over in weeks. We could reach herd immunity with a low contact rate alone, and reastaurants, schools, universities, airlines, could require test results and reopen quickly. Trump could go into the election with the number of cases and deaths crashing. He could campaign in empty hospitals. 

9 comments:

  1. Did you really mean "relatively inaccurate"?

    "Go to CVS, get the test kit, find out if you have it. No referral, no doctor visit, no prescription, no insurance, no faxed paperwork. Let private decisions figure out what to do with the results."

    Do you think the average person understands concepts such as sensitivity and specificity? Can they be relied upon to make informed decisions? What if their decision conflicts with what I think their decision should be? Do they have the right to ignore using masks and social distancing based on their uninformed interpretation of questionable test results and run around spewing contagion?

    The priority needs to be focused on a test with high sensitivity and specificity and the results discussed with a physician. For example the straight leg test for sciatica is highly sensitive. If you have sciatica the odds of a positive SLR test is high. Unfortunately the SLR test is not very specific. Many people with a positive SLR do not have sciatica. Do you trust people to make their own diagnoses using SLR?

    My own experience has been two completely asymptomatic individuals who tested positive and another with cough and fever who tested negative 3 times before succumbing to COVID-19 about 2 weeks later. So much for testing.

    Suppose you get test results back that show your potassium is 5.8. If thats real, you have a medical emergency since that could lead to cardiac dysrhythmia. OTOH a high potassium might be due to rupture of red blood cells while the sample is drawn, resulting in a false high result. Two very different outcomes. How many people understand what to do with a potassium level of 5.8? I can tell you one thing: my accountant didn't know until he emailed me his results.

    First we need a test with high sensitivity and specificity. Then we need to know what to do with the information. The decision should not be left to the uninformed patient with a test kit not vetted by the FDA.

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    1. Right now we are acting as if everyone has tested positive for the virus. I think flawed testing is better than no testing. It's not even clear that most people are complying with the sheltering place mandates. There are fans at football games.

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    2. Your examples highlight the exact distinction John is trying to make, though, between tests for the purposes of medical diagnosis and tests for public-health interventions. You have to apply decision theory and error-cost minimization to this problem. The sensitivity a test needs is directly proportional to the harm from a false negative (relative to a world without testing) and the specificity a test needs is directly proportion to the harm from a false positive (relative to a world without testing). So, in scenarios that you mention, where you are going to use the test to do something potentially dangerous if done to someone healthy, then absolutely you need tests with high specificity. For sure, no one should use a saliva test with low specificity to decide whether to give someone dexamethasone.

      But public-health interventions don't have the same harm profile. The risk to someone who receives a false positive is unnecessarily isolating for a couple weeks. That is inconvenient, but hardly dangerous. Especially so when the alternative to testing is a high degree of existing isolation.

      Similarly, the risk of a false negative is that a person spreads the virus. That is more dangerous, but one has to consider the alternative without testing. If the alternative without testing is a significant degree of social interaction with community spread, a test doesn't have to be very sensitive to help.

      Critically, this is true no matter how you strike the policy balance between the costs of social isolation and the costs of virus spread. For a community that has chosen maximal lockdown, the cost of false positives is de minimis, since everyone is essentially quarantined already, so the false positive rate can be sky high without much problem. On the other side, even a test that has a 50% false negative rate can help this community: it can now halve its social isolation while keeping the transmission rate the same.

      A community that has chosen "let it rip" can also benefit even from a very inaccurate test. A high false negative rate will have de minimis impact in this community, because no one is isolating anyway. On the other side, even a test with a high false positive rate can help this community: if people who take a test with 10% false positive rate just take basic precautions, transmission can fall dramatically with a relatively small number of people being inconvenienced.

      Real communities will be somewhere in between. But the point stands that the test produces benefits even when very inaccurate. For sure, the lower the false positive rate, the harsher the isolation you are likely to be able to sustainably impose on those who test positive or the fewer the people you will inconvenience; and the lower the false negative rate, the greater the relaxation of social isolation you can support or the lower the continuing transmission you will be able to achieve.

      South Korea is a good case study. They were able to rapidly introduce testing because they had a test kit designed to capture features common to all known coronaviruses. This test had terrible specificity. Huge numbers of people in South Korea were probably unnecessarily quarantined for a short period. But the benefits have been dramatic: life is much more relaxed than elsewhere while transmission is minimal.

      In addition, the cheaper the tests get, the more you can use multiple testing to compensate for flaws in the test's accuracy. For cheap tests with high false positive rates, multiple samples can be independently tested and a positive declared only when a sufficient number of them show positive. (Indeed, you could even calibrate precautions, a person with 1/5 positive must where a mask everywhere including at home, a person with 5/5 gets taken to a monitored quarantine facility.) For tests with high false negative rates, people can be tested more frequently.

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  2. Speaking as an average person I very much agree with the Scott Summer / Alex T view. But clearly, for reasons that you outline in a number of your posts, this isn't happening. Anywhere.

    Can we start something? E.g. in the US, is it impossible to get a low cost saliva based test? Would you be breaking the law? Is there a work around? It seems to me that if a few high profile people took this up it might catch (so to speak). I don't mean talking about it, I mean doing it. High profile is not thee and me - although it would be a start. But it needs some widely well known folks to get the ball rolling. Perhaps the US (and UK) are not the most promising places to start. But somewhere is.

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    1. Apologies, that should be Romer (rather than SumNer). But the point stands.

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  3. So, let's conduct a gedankenexperiment, a la Karl Shell, and imagine that you are a typical average American Joe. You wake up one morning feeling absolutely awful, your brain is in a 'fog', and your breathing is somewhat labored. You call your ex- and ask, "What should I do, honey?" She mulls that one over for a minute, and then replies, "Dear ex-, I've just finished reading about a grumpy economist's prescription for testing. Get yourself down to the nearest CVS, and buy one of those off-the-shelf 'COVID tests and follow the instructions. You know how to do that, Dear, don't you?" "Yes", you reply, "that's the solution!" So, you make your way to the nearest CVS, and you find the 'COVID' test products section--all over the counter stuff. There are ten different testing products, all for self-assessment, ranging in price from $9.99 through $95.98, per test. All are "guaranteed to work"; all are labelled "easy to use". Which one do you choose? The $9.99 one. So, you get home, you're feeling worse, but optimistic. You follow the directions and self-administer the test. You wait the stipulated 15 minutes for the device to cough up the test result. "Negative" for COVID-19, it states. "Whew!", you say, "You had me worried for a while there." Still, you're feeling worse now than ever before. Your breathing is more labored now than before. Your mind is in a deeper fog. You head to the couch to lie down for a spell. You've been sold a bill of goods. Snake oil, the real thing. No FDA, no guaranteed reliable results. Your ex- comes over and finds you laid out cold on the carpet--you never made it to the couch. 9-1-1 it is, and there you go, just another vital statistic. Such is life. You pay your money, and what do you get in return?--zilch. No FDA, no guarantee.

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  4. I am always amazed whenever I read novel and impeccable rhetoric on the "primal" nature of capitalism and the inexorable Orwellian dystopia it brings.

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  5. Why doesn't the administration say "free the tests?" My guess is a combination of (i) ignorance about the value and the way to accomplish that (which might not be easy) and (ii) concern about the short term political fallout of more cases. I'm not sure tests are a panacea, but I'd sure allow people to find out by "freeing the tests."

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  6. "the most radical and ruthless of the political groups formed in the wake of the French Revolution, and in association with Robespierre they instituted the Terror of 1793–4." As a member of the Committee of Public safety, Robespierre suborned terror all the while putting his own head at risk. Old Max met Madame Guillotine on the 28th of July, 1794.

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