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Posts mislead on PCR test development

February 21, 2022 GMT

CLAIM: COVID-19 PCR tests weren’t developed using samples of the coronavirus and instead detect “something else.”

AP’S ASSESSMENT: Partly false. A PCR test created by the Centers for Disease Control and Prevention at the beginning of the pandemic was developed with genetic sequencing of the coronavirus, rather than actual samples. But experts say that is a normal method, and the test was still designed to detect the virus and was proven effective in studies.

THE FACTS: Misleading posts circulating widely online in recent days are using technical documents from one COVID-19 PCR test to falsely claim that such tests don’t actually detect the coronavirus – with some users going so far as to suggest they instead pick up the common cold or flu.

“FDA document admits ‘Covid’ PCR test was developed without isolated samples for test calibration, effectively admitting it’s testing something else,” one Twitter user wrote in a Feb. 14 tweet that was shared over 12,000 times. The claim has also circulated on Facebook and Telegram.

To support the claim, social media users shared the “Instructions for Use” for the PCR, or polymerase chain reaction, COVID-19 test released by the CDC in early 2020, as the virus was first emerging in the U.S. The document notes that “no quantified virus isolates of the 2019-nCoV were available for CDC use at the time the test was developed.”

But the test is still accurate and was still developed to detect the coronavirus that causes COVID-19 – and not “something else” like the cold or flu, according to an expert and a spokesperson for the U.S. Food and Drug Administration.

The CDC test did not use an actual sample of the coronavirus because samples were unavailable at that early time in the pandemic. However, the agency instead relied on genetic sequencing of the virus to determine the test’s effectiveness, which is a common practice, according to Matthew Binnicker, director of the clinical virology lab at the Mayo Clinic in Rochester, Minnesota.

“During the initial days of an emerging disease outbreak, it may be difficult for public health laboratories (and diagnostic test manufacturers) to gain access to actual clinical samples from patients who are infected with a novel agent,” he wrote in an email to the AP. “This type of approach is not uncommon when a new diagnostic test needs to be rapidly developed during an outbreak of a novel pathogen, and it is scientifically accepted, robust, and legitimate.”

Binnicker added that the genetic sequence used to design the test was not the same sequence as other coronaviruses, such as the common cold. James McKinney, a spokesperson for the FDA, which authorizes PCR tests, concurred the cold virus was “never used as a substitute for SARS-CoV-2 in validation studies.”

“Although not isolated from clinical samples, the material used to analytically validate the test is representative of SARS-CoV-2, and demonstrates the ability of the test to detect SARS-CoV-2 in patient samples,” he wrote in an email to the AP.

As the AP has previously reported, tests authorized for emergency use in the U.S. must meet strict criteria for accuracy. In addition to studies demonstrating that the CDC test only detected the coronavirus, the test also underwent a clinical study “evaluating respiratory samples from patients suspected of COVID-19,” McKinney wrote.

McKinney noted that the document cited by social media users features a table showing that the test did not detect other respiratory pathogens.

Hundreds of different COVID-19 tests have since been authorized by the FDA, according to the agency’s website. And all that were authorized by the agency after May 2020 were “validated” with samples of the coronavirus, according to McKinney.

Meanwhile, the CDC announcedin July 2021 that it would “retire” the test being cited on social media in favor of newer tests that can detect multiple viruses, not just the coronavirus, the AP reported. The CDC did not respond to the AP’s request for comment.


This is part of AP’s effort to address widely shared misinformation, including work with outside companies and organizations to add factual context to misleading content that is circulating online. Learn more about fact-checking at AP.