Yesterday, Andy Swan invented a COVID story and watched it go viral.
The text he screenshot literally says nothing about false positives, nor does the underlying document. Nevertheless, it got at least 10,875 retweets before being deleted. It was echoed not just by careless COVID cranks like Ethical Skeptic and Kyle Lamb, but by broader conservative media like Julia Hartley-Brewer, David Samadi, Steve Deace, and disclose.tv. Some invented even more details out of whole cloth, claiming that WHO recommended a reduced cycled count or even that a specific cycle threshold should be used.
In this article, I discuss two things (1) why this is nonsense, and (2) how its spread shows we are still living in the QAnon age of viral misinformation.
Background on PCR
The WHO notice is a bulletin to lab workers who run polymerase chain reaction (PCR) tests for SARS-CoV-2, the virus that causes COVID-19.
Real-time PCR works amplifying DNA. Enzymes duplicate DNA segments in between “primers,” short DNA fragments, specific to the genes of interest. (Because SARS-CoV-2 is an RNA virus, it is first transcribed into DNA using a reverse transcriptase enzyme before PCR occurs).
The “cycles” of PCR are temperature cycles—the reaction vessel is periodically heated above 90°C, so that duplicated strands of DNA denature—become separated from each other—then cooled so that primers can reattach at the same points to allow more copies to be made. Virologist Ian Mackay has an excellent post on this topic.
Additional cycles mean additional amplification of the target DNA, but this does not create false positives. PCR primers are chosen to be specific to gene sequences virus, and so PCR will not show positive even after an arbitrarily large number of cycles, except through handling errors.
COVID minimizers usually retreat from their “false negative” accusation by saying, “well I mean it’s picking up old infections with low viral loads that couldn’t infect anyone.” And it may! But this isn’t a false positive.
COVID minimizers theorize that most PCR positives must have very weak positives, but actual data shoot a hole through this myth as well. Minimizers say things like “anything over 30 Ct is a false positive.” Well, by that definition, in times of widespread infection (like now), the vast majority of PCR positives are “true positives” representing likely-infectious patients:
One tradeoff is that highly sensitive PCR is needed for contact tracing—for catching people in the early stages of the disease who may also have low viral loads. Interpreting test results is a different question from demanding that labs bowdlerize PCR tests to make them less sensitive, which is what many cranks seem to want.
Nothing new in the WHO guidance
So returning to the WHO notice—which is written for technicians and not the public—it doesn’t say anything like what’s claimed. The milquetoast document doesn’t say that cycle thresholds should be reduced and certainly doesn’t say that high thresholds are “false positives.”
Where the hell are they getting any of this?
Fortunately, “Ethical” Skeptic highlighted the part of the notice he thinks damning:
The problem is, this still doesn’t suggest anything about “false positives” and isn’t new besides. You get the same gist from the prior version of the same document published on December 7:
This means that the probability that a person who has a positive result (SARS-CoV-2 detected) is truly infected with SARS-CoV-2 decreases as positivity rate decreases, irrespective of the assay specificity. Therefore, healthcare providers are encouraged to take into consideration testing results along with clinical signs and symptoms, confirmed status of any contacts, etc.
… The design principle of RT-PCR means that for patients with high levels of circulating virus (viral load), relatively few cycles will be needed to detect virus and so the Ct value will be low. Conversely, when specimens return a high Ct value, it means that many cycles were required to detect virus. …
Consider any positive result (SARS-CoV-2 detected) or negative results (SARS-CoV-2 not detected) in combination with specimen type, clinical observations, patient history, and epidemiological information.
There’s [almost] nothing new in the January 20 version of this document: patients’ symptoms should be considered for diagnosis. And none of it would have been new to technicians in December either—PCR operators and virologists understand that later positives suggest lower viral load.
EDIT 1/22: Economist Andreas Backhaus pointed out to me there is one significant change: WHO now explicitly recommends that asymptomatic positives be retested. Maybe doctors were already doing this (as suggested by the earlier language about considering multiple test results), but it is a new WHO recommendation. Perhaps this marginally reduces case counts. If it does, case fatality rates will look worse.
Lots of conservatives, including Swan, claimed that the WHO notice was connected to Biden’s inauguration, providing yet another example of my earlier post that the narrative about COVID-19 hasn’t changed as much as the conservative media narrative about it. The WHO document last month contained all of the supposedly surprising admissions, but it didn’t go truly viral until Andy Swan invented the hook for his tweet, which leads me to my next point.
We are still living in a QAnon-poisoned world
Among all of the “bluecheck” accounts not yet banned by Twitter, Andy Swan may have been the most friendly toward QAnon conspiracy theory. He certainly promoted nearly every voter fraud myth that came down the pike. I think he’s avoided scrutiny because he deletes all of his tweets within days of posting (include the one at the top of this post).
When I saw his tweet yesterday, it reminded me of the “only 6% died” myth popularized by a QAnon follower:
While Trump no longer has accounts on mainstream social media platforms, and while it’s fun to point at disappointed and confused QAnon followers, not much has actually changed. Former QAnon people are still around and still share the country with non-QAnon folks. More importantly, the broken incentives that encourage misinformation still exist.
This is a generic problem with social media, and so we shouldn’t expect a reprieve just because QAnon and kraken theorists were wildly, hilariously wrong. Lies remain easier to crank out than accuracy, and lies can be tailored to go viral in a way that sober reporting rarely permits.
Stay cautious my friends. Don’t amplify stories you haven’t scrutinized—especially when the stories confirm your beliefs.