Vanessa Abrahamson Blog: Viral Posts Misrepresent CDC Announcement on COVID-19 PCR Test

SciCheck Digest

Scientists consider polymerase chain reaction, or PCR, tests a highly reliable tool for diagnosing COVID-19. But social media posts are misrepresenting a recent Centers for Disease Control and Prevention announcement regarding the eventual discontinuation of its own test, falsely claiming the government has conceded that PCR tests aren’t reliable.

Tests that detect current infections with SARS-CoV-2, the virus that causes COVID-19, are known as viral tests. There are two types: a Nucleic Acid Amplification Test, or NAAT, and an antigen test.

Many of the NAATs use a molecular biology technique known as the polymerase chain reaction, or PCR, to detect even a very tiny amount of the virus in a specimen.

The PCR test takes advantage of some natural features of biology to essentially scan through all of the RNA present in a sample — such as a nasal swab — and search for the presence of coronavirus RNA.

The Centers for Disease Control and Prevention says NAATs “are unlikely to return a false-negative result of SARS-CoV-2,” and it recommends only laboratory-based NAATS, the most sensitive tests, to confirm infection. It also says saliva tests aren’t as optimal as those using swabs of the nose or nasopharynx (upper throat behind the nose).

An antigen test is designed to detect the coronavirus antigen, a structure on the surface of the virus that triggers an immune response. Also conducted via a nasal or throat swab, antigen tests are less sensitive than NAATs but inexpensive and can usually produce results in about 15 minutes. Getting a result from a NAAT test can take about an hour or even a few days.

Testing can help stop the spread of the coronavirus from those who test positive, because they can then isolate themselves from others. But, as we’ve explained, testing has its limitations. It can take a few days or even longer after exposure to the virus before it’s detectable by the diagnostic tests. So even some with negative results could be infectious.

Still, to help limit the spread, the U.S. has instituted travel requirements and recommendations. All international airline passengers, including U.S. citizens and residents, and those who are fully vaccinated, arriving in the U.S. must show “a negative COVID-19 test, taken within three (3) calendar days of departure, or proof of recovery from the virus within the last 90 days,” as the State Department explains.

The CDC also recommends that everyone, including the fully vaccinated, get a viral test three to five days after returning from international travel.

The CDC recommends that those who aren’t fully vaccinated avoid international travel, and if they must travel, to get a test one to three days beforehand. The unvaccinated also should self-quarantine for seven days after returning to the U.S., even if they tested negative before or upon returning.

International destinations may have their own testing requirements as well.

As for domestic travel, the fully vaccinated don’t need to get tested, but the CDC recommends the unvaccinated follow the same guidelines as those for international travel.

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In the early days of the COVID-19 pandemic, the Centers for Disease Control and Prevention developed and deployed its own polymerase chain reaction, or PCR, test to identify infections with the novel coronavirus (although its initial rollout was beset with some issues).

A year and a half later, the federal agency has notified labs that it will — at the end of 2021 — withdraw its emergency use authorization request for the test to the Food and Drug Administration, thereby discontinuing its use.

The agency in a July 21 notice recommended that labs use “one of the many FDA-authorized alternatives” and said it “encourages laboratories to consider adoption of a multiplexed method that can facilitate detection and differentiation of SARS-CoV-2 and influenza viruses.” Such multiplex tests, including one from the CDC, can look for both the novel coronavirus and multiple types of influenza at the same time — which conserves testing materials and allows public health labs to do influenza surveillance while testing for SARS-CoV-2, or the virus that causes COVID-19.

But the CDC did not say it was no longer supporting the use of PCR tests in general, many of which have been authorized by the FDA — or that its original PCR test for SARS-CoV-2 can’t tell the difference between coronavirus and influenza — as viral posts spreading online falsely claim.

“After 180 million positive cases, the CDC have announced their withdrawal statement from using the PCR test to detect Covid, due to its lack of detection to differentiate between Covid and Influenza,” read a July 25 tweet screenshot posted to Instagram. The post received more than 4,000 likes.

A July 26 Facebook post similarly claimed: “Big News-CDC withdraws PCR test from FDA EUA. It’s inability to differentiate Covid from Influenza was #1 reason.”

The CDC’s PCR test in question looks only for SARS-CoV-2, not influenza — which is quite different from a test that mistakenly diagnoses influenza cases as COVID-19, as the posts erroneously suggest.

Other posts have falsely claimed it was the FDA that made the purported revelation about the CDC’s PCR test, or PCR tests in general.

A since-deleted July 23 tweet from “UK Medical Freedom” falsely claimed that the “FDA announced today that the CDC PCR test for COVID-19 has failed its full review. Emergency Use Authorization has been REVOKED.”

Two days later, on July 25, a controversial gym owner in New Jersey, Ian Smith, falsely claimed in a viral tweet that the “FDA confirms PCR tests not accurate for testing COVID.” He referred to COVID-19 as a “Manufactured crisis.”

As we said, the announcement in question came from the CDC and was about plans for the eventual discontinuation of its own test. It is still in use currently. The FDA did not revoke the CDC test’s emergency use authorization or question the reliability of PCR tests, an FDA spokesman confirmed to us.

Scientists consider PCR tests a reliable and highly specific diagnostic tool, as we’ve explained before, but distortions about them have persisted amid the COVID-19 pandemic.

In explaining the CDC’s decision to end the use of its own PCR test at the end of 2021, Kristen Nordlund, an agency spokeswoman, in an email to us cited “the availability of commercial options for clinical diagnosis of SARS-CoV-2 infection, including multiplexed (discussed here) and high-throughput options” — referring to technologies that use an automated process to administer hundreds of tests per day.

“Although the CDC 2019 Novel Coronavirus (2019 nCoV) Real-Time RT-PCR Diagnostic Panel met an important unmet need when it was developed and deployed and has not demonstrated any performance issues, the demand for this test has declined with the emergence of other higher-throughput and multiplexed assays,” Nordlund said.

She continued: “CDC is encouraging public health laboratories (PHL) to adopt the CDC Influenza SARS-CoV-2 (Flu SC2) Multiplex Assay to enable continued surveillance for both influenza and SARS-CoV-2, which will save both time and resources for PHL.”

The FDA’s website lists a multitude of PCR tests for COVID-19 that have been issued emergency use authorizations.

Jim McKinney, an FDA spokesman, told us in an email that to date, “the FDA has authorized more than 380 tests and sample collection kits to diagnose COVID-19, many of which are PCR tests. PCR tests are generally considered to be the ‘gold standard’ for COVID-19 diagnosis.”

“The FDA has not issued any statement questioning the reliability of PCR test results in general and will continue to consider authorization for validated PCR tests,” he added.

Dr. Michael Mina, a Harvard University assistant professor of epidemiology, told us that the CDC’s decision regarding its test made sense, given how the landscape has changed.

“CDC is likely going to pull its own EUA for its test because hundreds of other labs now have their own EUAs and CDC no longer even needs to use its own test since many companies now have EUAs for manufactured tests,” he said in an email. “The major Companies like Roche, Hologic, Abbott all have their own test kits and instruments. Then the ThermoFishers of the world have EUAs for their PCR kits that can be run in the exact same way as the CDC assay. So there really is no reason for CDC to retain their EUA.”

Mina said the move had to be done carefully, since some public health labs may currently be relying on the CDC’s test.

“At the end of the day, the CDC EUA was more or less a recipe for how to test for CoVID, and a couple ingredients,” Mina said. “Now we have all these kits and fully automated processes so it’s no longer needed.”

Editor’s note: SciCheck’s COVID-19/Vaccination Project is made possible by a grant from the Robert Wood Johnson Foundation. The foundation has no control over our editorial decisions, and the views expressed in our articles do not necessarily reflect the views of the foundation. The goal of the project is to increase exposure to accurate information about COVID-19 and vaccines, while decreasing the impact of misinformation.

Sources

“07/21/2021: Lab Alert: Changes to CDC RT-PCR for SARS-CoV-2 Testing.” Centers for Disease Control and Prevention. 21 Jul 2021.

“CDC 2019-nCoV Real-Time RT-PCR Diagnostic Panel – Letter of Authorization.” Food and Drug Administration. Accessed 26 Jul 2021.

“CDC Diagnostic Tests for COVID-19.” Centers for Disease Control and Prevention. Updated 5 Aug 2020.

Fichera, Angelo. “Viral Posts Distort WHO Guidance on COVID-19 Tests.” FactCheck.org. 29 Jan 2021.

“In Vitro Diagnostics EUAs – Molecular Diagnostic Tests for SARS-CoV-2.” Food and Drug Administration. Accessed 26 Jul 2021.

“Influenza SARS-CoV-2 (Flu SC2) Multiplex Assay — Letter of Authorization.” Food and Drug Administration. 2 Jul 2020.

McKinney, Jim. Spokesman, Food and Drug Administration. Email to FactCheck.org. 26 Jul 2021.

Mina, Michael. Assistant professor of epidemiology, Harvard University. Email to FactCheck.org. 26 Jul 2021.

Nordlund, Kristen. Spokeswoman, Centers for Disease Control and Prevention. Email to FactCheck.org. 26 Jul 2021.

“Shipping of CDC 2019 Novel Coronavirus Diagnostic Test Kits Begins.” Press release, Centers for Disease Control and Prevention. 6 Feb 2021.

Steele, Allison. “Atilis Gym owners break into their own business to let in customers, again violating N.J.‘s coronavirus orders.” Philadelphia Inquirer. 1 Aug 2020.

Willman, David. “The CDC’s failed race against covid-19: A threat underestimated and a test overcomplicated.” Washington Post. 26 Dec 2020.

The post Viral Posts Misrepresent CDC Announcement on COVID-19 PCR Test appeared first on FactCheck.org.

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