The recent posts have sparked some nice discussion here and elsewhere. This post collects additional comments I've since made.
Excess deaths caused by the lockdown
There was a verbal scuffle when reporter Jonathan Swan interviewed President Trump a few weeks ago about how to measure deaths due to Covid-19. Should we look at deaths per case (mortality rate) or deaths per million? In two recent posts (1 and 2), I discussed the visualization and modeling of "excess deaths," which is a better way of measuring the pandemic's impact than both of those popular metrics.
The starting point of an excess death analysis is neutral and apolitical. Based on historical patterns, we know that X people tend to die in the weeks from March to the present. Instead of X, the actual deaths (by any cause) have spiked in most U.S. states by 50% to 700% of the normal level in the worst weeks of the pandemic.
These "excess deaths" are not explained by any of the known causes. A majority of these deaths can be explained by deaths attributed to Covid-19, a novel cause of death. Most scientists believe that the unexplained excess deaths are probably under-counts of Covid-19 deaths. Should convincing data emerge, other causes of deaths could be accepted.
Some readers asked whether "excess deaths" may be caused by the lockdown rather than the virus. The lockdown does not kill anyone directly. What they mean is the side effects of the lockdown, such as more suicides from depression due to lockdown, or more cancer deaths because the patients were turned away from hospitals.
This is a logical argument but let me explain why this argument seems like a dead-end:
- The biggest challenge is the scale of the gap. A 50-percent to 700-percent gap is not easy to reconcile. Cancer is 20 percent of all U.S. deaths in 2017 (source). Let's say half of those occur between March and July. Then, if 2020 is similar to 2017, we should expect 300,000 deaths during those months. If we want cancer to explain 100,000 excess deaths, we're saying the lockdown caused cancer deaths to rise by 33 percent. That's a huge jump for a well-known disease that requires investigation. And we still have another 100,000 excess deaths to explain.
- Other than rhetoric and anecdotes, I haven't come across any serious attempt to quantify these lockdown side-effects. If some cancer patients have died because they are turned away from hospitals, then they should start investigating people who died at home from late-stage cancer. How many such deaths can we confirm? It's plausible that such deaths exist but I doubt this will make a dent in explaining the 200,000 excess deaths.
- Most cancer patients who died at home because they couldn't schedule surgery at the hospital during the pandemic were seriously ill, and would have died eventually of cancer. The side effect of the lockdown is accelerated deaths. In the world of "excess deaths," an accelerated death contributes to one positive excess death now and one negative excess (avoided) death later. After lockdown is called off, we should experience a reversal of these excess deaths. Will we find hundreds and thousands fewer deaths from all non-Covid19 causes in the aftermath? I don't think so.
False positives in the NFL
News broke that many recent positive test results on NFL players turned out to be false positives. This has been described as a "testing debacle."
First thought: false positives are the price to pay for being able to trust negative results. Notice that the NFL is not re-testing negative results; the NFL retests positive results. In order to afford such a luxury, the negative results must be rock solid. If the test comes back negative, the person is more or less certain to not be infected. This is how a good coronavirus test should behave. A false-negative mistake is an infectious person who spreads the virus unknowingly. For a diagnostic test to have fewer false negatives, it will have more false positives.
Second thought: testing errors, when interpreted in a broad sense, can be caused by operational mishaps. From what has been disclosed so far, it appears that the NFL contracts a single private testing company to perform all coronavirus testing, and that business operates labs in multiple states. All the false positives came from the New Jersey lab. This might be traced to say a contamination of equipment at the lab, just for argument [PS. That's the official reason given by the lab now.]. If true, the inaccuracy has nothing to do with the chemistry; the error came from lab operations.
All accuracy metrics published by test developers assume zero operational mishaps, 100 percent complicance, no gaming, etc. I brought this important point up in Chapter 4 of Numbers Rule Your World (link) - an entire chapter devoted to the complex issue of testing accuracy.
This is why when discussing group testing in this post, I singled out operational mishaps that could happen because group testing adds complexity.
Wishful thinking on treatments
The U.S. President has endorsed plasma therapy as the latest best therapy for Covid-19. The FDA has given it emergency use authorization. We should be clear that this is temporary, pending the results of proper scientific testing, with randomized controlled trials that prove plasma works.
I understand the media love the feel-good stories about people who insist that plasma saved their lives. But these survivors don't know. Because if plasma indeed saved their lives, then had they not been given the blood transfusion, they would have died. But no one knows that since they got the plasma!
It is entirely possible that plasma worked for some specific cases. The point of science is to establish that it would make a difference for enough patients to matter. [PS. The FDA Commissioner has already sort of back-tracked.]
Elsewhere, on college campuses and in professional sports, the testing labs are turning to quick saliva tests to scale up testing. This is of course a good thing. There are several such tests developed (I think I've read about those made by Yale, University of Illinois, Rutgers, etc.). The developers of these tests make many magical claims (see here). The quick test is supposed to be just as accurate as the nasal swab PCR test; much faster than that test; can pick up even lower amounts of virus; can provide a numeric scale of the amount of virus, not just its presence or absence; etc.
I find these claims hard to believe, except the efficency claim. Saliva should contain less materials mixed with unrelated fluids. It's probably less accurate. But the benefit of scale is obvious. Since it's used primarily for "surveillance testing", let's hope it doesn't generate too many false negatives, who become silent carriers.
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