PCR tests are used to amplify and detect genetic material from SARS-CoV-2, which causes COVID-19. 

Wild claims about CDC PCR alert don’t pass the test

AAP FactCheck July 29, 2021

The Statement

Social media posts claim the US Centers for Disease Control and Prevention (CDC) withdrew authorisation for PCR tests to be used to detect COVID-19 because they couldn’t tell the difference between influenza and the coronavirus.

One post, from the Instagram account of Australian personal trainer Ali Haydar, includes text which says: “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. So at this point, conspiracy theories might as well be called spoiler alerts.”

Similar claims, including that the test “failed its full review”, have been shared by multiple other users in Australia, including by former Neighbours actor Nicola Charles, Sydney law firm G&B Lawyers and Will Connolly, best known as “Eggboy” for hitting former Australian senator Fraser Anning with an egg.

The Instagram post from July 25
 A post claims PCR tests have been withdrawn because they can’t differentiate COVID-19 from flu. 

The Analysis

The CDC recently announced it was withdrawing its polymerase chain reaction (PCR) test from use at the end of the year. However, despite the social media claims, this was not due to the test failing a review or concerns that it was returning false results.

Rather, the CDC said demand for the test had declined to newer alternatives, which had the ability to detect multiple viruses and therefore save valuable laboratory resources.

The CDC released a laboratory alert on July 21 stating that it would withdraw a request to the US Food and Drug Administration (FDA) for emergency use authorisation of the CDC 2019-Novel Coronavirus (2019-nCoV) PCR test, which was introduced in February 2020 at the beginning of the coronavirus pandemic.

PCR testing involves the selective amplification of genetic material to identify specific DNA; in the case of COVID-19, the material is transcribed RNA material from the SARS-CoV-2 virus. Different primers or probes can be used in the testing process to detect various viruses or bacteria.

The CDC alert said the agency encouraged “laboratories to consider adoption of a multiplexed method that can facilitate detection and differentiation of SARS-CoV-2 and influenza viruses”. Multiplex PCR tests enable the detection of more than one pathogen.

“Such assays can facilitate continued testing for both influenza and SARS-CoV-2 and can save both time and resources as we head into influenza season,” the alert continued.

Both the CDC’s alert and FDA guidance on the same CDC test clearly state the test was designed only to detect SARS-CoV-2 and make no mention of it having the potential to falsely identify influenza as the coronavirus.

In a statement to AAP FactCheck expanding on the announcement, a CDC spokeswoman said the agency planned to discontinue its support for the test “given the availability of commercial options for clinical diagnosis of SARS-CoV-2 infection, including multiplexed and high-throughput options”.

“Although (the test) 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,” she said.

Ellen Foxman, an assistant professor of laboratory medicine and immunobiology at the Yale School of Medicine and principal investigator for the school’s Foxman Lab, which examines viral infections, said it was “very well established” that the CDC PCR test detected COVID-19 and not influenza.

“(It) is reliable and specific for COVID-19. PCR tests are designed to test for the presence of a specific virus based on its genome sequence. The sequences detected by the CDC COVID-19 PCR test are not present in the influenza virus,” she told AAP FactCheck in an email

Dr Foxman added that it was likely the CDC was not pursuing FDA approval for the test as there were already numerous other FDA-approved COVID-19 tests available, including ones that also tested for influenza.

“For symptomatic individuals in the flu season, it is best to use a dual test that can detect both COVID-19 and influenza, not a test that only detects only COVID-19,” she said.

The alert only relates to the CDC test and does not apply to PCR testing for COVID-19 overall, despite claims in some posts to that effect. It does not highlight flaws with the test as being the reason for its withdrawal.

A similar misleading claim to those in the posts was raised in Australia on July 27, when Victoria’s chief health officer Brett Sutton was asked at a press conference about the CDC finding that PCR tests could not distinguish between COVID-19 and influenza. (video mark 1hr 9min 30sec)

Professor Sutton responded that all positive COVID-19 tests in the state went through quality-assurance processes to ensure they were “unequivocally” true positives.

A Victorian Department of Health spokeswoman told AAP FactCheck in an email that the tests used in the state and elsewhere in Australia successfully differentiated between SARS-CoV-2 and influenza.

“The genetic sequences of these two viruses are very different from each other,” she said. “The PCR tests for SARS-CoV-2 have an extremely high degree of specificity because the tests target genetic sequences unique to SARS-CoV-2.”

Australian Nobel laureate Peter Doherty, a professor of immunology, tweeted after the question to Prof Sutton: “The COVID-19 PCR test discriminates SARS-CoV-2 from any other virus, including all human (coronaviruses).”

Similar misleading claims about the CDC’s withdrawal of emergency use authorisation for the PCR test have been debunked by other fact checking organisations here, here and here.

AAP FactCheck has also dealt with other misleading claims about PCR testing for COVID-19, including that the tests return high numbers of false positives and contain toxic substances.

The Verdict

The CDC has not declared that its PCR test or any similar tests for COVID-19 cannot differentiate between influenza and the coronavirus, nor did the test fail a review as claimed.

The CDC said the test was not being withdrawn for any issues relating to its performance. Rather, it is withdrawing its initial test from use due to the widespread adoption of newer PCR tests which enable laboratories to simultaneously test for COVID-19 and influenza viruses, saving time and resources.

False – Content that has no basis in fact.

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