WHO did not say PCR tests grossly inflate positive test numbers

A conservative news site mischaracterized a message from the World Health Organization, claiming that the United Nations agency owned up to supporting a coronavirus test that resulted in huge numbers of false positives. 

"An hour after Joe Biden is sworn in, WHO admits their testing grossly overstates individuals testing positive for COVID," reads the headline of an article published by the Gateway Pundit.

The article links to a tweet by user Andy Swan, which in turn references a Jan. 20 notice that the WHO released to lab technicians. 

Did the WHO really make such an admission? No. This article was flagged as part of Facebook’s efforts to combat false news and misinformation on its News Feed. (Read more about our partnership with Facebook.) 

The notice cautions lab technicians that positive results should be interpreted with care and in the context of other information, such as clinical observation and patient history, to reduce the risk of false positives.

The notice — dated Jan. 13 and published on the site Jan. 20, according to the timestamp on it — is written in highly technical language. But five virologists, most of whom work in COVID-19 testing labs, told us that the gist of it was to remind lab technicians to carefully read the user manuals that come with PCR tests, the most widely used diagnostic tests for the coronavirus. 

"This is not new information. This is essentially a reminder from the WHO to testing laboratories," said Jonathan Jarry, a science communicator with the McGill University Office for Science and Society. "This notice is not an admission that the PCR test for COVID-19 does not work or is wildly inaccurate." 

Coronavirus tests are performed on samples of cells taken with a swab from the back of the throat. The lab isolates the genetic material from those cells and analyzes it for traces of the virus.

PCR tests, considered the most reliable, work by duplicating the genetic material in cycles until traces of the virus become more easily detectable. If there’s a large presence of virus in the sample, fewer cycles would be required to detect it, said Davidson Hamer, a professor of medicine at Boston University. 

The number of cycles required to detect the virus in a sample is known as a "cycle threshold." A low cycle threshold implies that a patient has a high risk of spreading the coronavirus to others.

The question for lab technicians is how many times to duplicate a particular sample before determining whether it is positive or negative. 

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"Once you get up there in cycles, you can start detecting very small concentrations of virus," Hamer said. 

As a result, a sample that tests positive after many amplification cycles is more likely to be a false positive than a sample that tests positive after fewer cycles. Nevertheless, Hamer said, false positives with PCR tests, even those with relatively high cycle thresholds, remain rare. 

"PCR tests are considered the gold standard of diagnostic tests," said Maureen Ferran, an associate professor of biology at the Rochester Institute of Technology. 

Joshua Sharfstein, vice dean at the Johns Hopkins Bloomberg School of Public Health, cautioned against viewing a low cycle threshold value as a strict indicator of high infectivity,  because some samples are less representative of the patient’s overall viral load than others. 

"It depends on how good the sample is," he said. The cycle threshold value "will measure the viral load for a particular sample, but not necessarily a patient." 

In addition, the amount of cycles required to determine whether a patient is positive varies among different types of PCR tests. 

"There are different tests that have different thresholds," said Ben Neuman, a Texas A&M University-Texarkana virologist. "Each lab knows where the thresholds are, and it’s their job to give you the results of your test based on their setup." 

That’s why the WHO notice urges lab technicians to view weak positive test results (ones with high cycle thresholds) with caution and to consult the instructions on their PCR machinery before issuing positive or negative test results.

Gateway Pundit did not respond to our request for comment.

A Gateway Pundit article claims that the "WHO admits their testing grossly overstates individuals testing positive for COVID," citing a notice from the organization.

However, the notice cited by the article is a reminder to lab technicians to carefully read the user’s manuals that come with PCR tests to ensure that results are interpreted correctly. It is not an admission that PCR tests don’t work or result in huge numbers of false positives.

This claim is False. ​