‘Covid test isn’t a Geiger counter’ says Russia’s ex-health czar after Elon Musk brings up PCR false positive rates
As SpaceX and Tesla mogul Elon Musk struggled to figure out false positive rates of rapid Covid-19 tests, Russia’s former chief health inspector said that declaring people infected after a single positive result was poor practice.
Musk, 49, embarked on a quest to sort out the possible false positive rates of polymerase chain reaction (PCR) testing, after getting two positive and two negative results in the same day.
“Same machine, same test, same nurse. Rapid antigen test from BD,” Musk tweeted out, sending social media into a frenzy on Friday.
He was still at it in the afternoon, soliciting information on accuracy of PCR tests, average false positive rate, and whether it’s “possible to generate a false positive if you simply run enough cycles.”
Would be great to hear from people who know a lot about the PCR testing industry. What’s the approximate false positive rate, all things considered, for cov2 PCR tests?
— Elon Musk (@elonmusk) November 13, 2020
The flurry of responses involving statistics, number of cycles and reliability intervals also spawned media coverage of the issue. Commenting on Musk’s tweets, former chief health inspector of Russia Gennady Onishchenko – now a member of the State Duma – reminded reporters that doctors used to require multiple positive tests before declaring someone infected.
“The test is not a Geiger counter, not a unit of measurement,” Onishchenko told the outlet Nation News. He brought up the HIV testing, which in Russia required three positive tests in a row and a final reference test to confirm infection – a far cry from rapid tests for the SARS-CoV2 virus currently rolled out across the West.
Hello Elon, PCR Cycle Threshold above 34 is non-infectious. Above 34, any RNA detected indicates dead virus, likely past exposure, almost a seroprevalence test. Below 24, 100% reliable. 24<>34 rapidly decreasing reliability. https://t.co/0MkiMkSSWs
— therealarod1984 (@therealarod1984) November 13, 2020
Onischenko was the first chief of Russia’s health and consumer protection watchdog Rospotrebnadzor, from its founding in 2004 to 2013.
Russia’s insistence on verifying coronavirus infections and performing autopsies on victims rather than going off single tests may account for the disproportionately lower number of cases, as well as deaths, than in the US.
So far, Russia has registered 1.86 million cases and just over 32,000 deaths in a population of 145 million, compared to 10.7 million cases and over 244,000 deaths attributed to the virus in the US, which has 330 million inhabitants.
The discrepancy led to some US media outlets to accuse Moscow of tampering with records, as Bloomberg did in May in a story headlined “Experts Want to Know Why Coronavirus Hasn’t Killed More Russians.”
Musk has presumably been testing ahead of the launch of SpaceX’s Crew Dragon to the International Space Station, originally scheduled for Saturday morning but delayed to Sunday evening due to weather concerns. He said he had symptoms of a “typical cold” but was otherwise not exhibiting any health problems commonly linked to Covid-19.
The rising number of “cases” – i.e. positive tests – has prompted several US governors to impose stricter lockdown measures on their states ahead of Thanksgiving holidays later this month.
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