A number of posts on Facebook have made claims about the man who invented PCR tests, Dr Kary B. Mullis, and what that means about Covid-19 testing. One such post claims:
“[Dr Mullis] said that this PCR test was not made to detect any type of infectious disease. It’s designed to pick up a signature of DNA and RNA of the person being tested.”
There is absolutely no evidence that the inventor of the PCR process said this. PCR is used for a number of scientific processes, and in general, it amplifies bits of genetic information so that they can be detected within samples. But PCR tests are specific to the DNA they are testing for, whether that’s of a person or a virus, so aren’t “designed” to pick up the genetic material of the person being tested.
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What is PCR?
In the UK, testing to see whether someone currently has Covid-19 is performed using an extremely common process called PCR, and known as a PCR test. This involves taking a swab from someone’s throat and nose, and then using PCR to detect the genetic material of the virus that causes Covid-19 (which is called SARS-CoV-2).
PCR, or polymerase chain reaction, is just the process by which this genetic material can be detected by scientists. The laboratory doing the testing adds a very specific substance to the sample, and if the sample contains any SARS-CoV-2, this substance triggers a chain reaction that creates enough copies of the genetic material so that it can be detected through analysis.
PCR was indeed invented by a man called Kary B. Mullis, who died in August 2019 long before Covid-19 began to spread in December 2019.
He didn’t say PCR testing couldn’t be used for testing for any diseases, as some social media posts claim. Confusion seems to have arisen from quotes of his in a 1996 article about HIV and AIDS. In this, neither the author of the article, nor Dr Mullis said PCR testing does not work or only identifies the DNA or RNA of the person being tested.
The author actually quotes Dr Mullis as saying “Quantitative PCR is an oxymoron” within the context of testing viral load (the amount of virus present) in people with HIV. This doesn’t mean he thought PCR testing didn’t work at all, but that there are limitations in detecting the specific levels of a virus from a sample using PCR testing.
Fact checkers at Australian Associated Press say that when the quotes about PCR testing picking up the DNA of the person being tested first appeared online, they were “not attributed to Dr Mullis but to an online commenter called "VirusGuy"”.