A post on Facebook claims that Kary Mullis, the inventor of the biotechnological process of PCR said the following: “Anyone can test positive for practically anything with a PCR test, if you run it long enough with PCR if you do it well, you can find almost anything in anybody. It doesn’t tell you that you’re sick.”
We could find no record of him saying the exact quote anywhere, except in other fact checkers debunking his comments. But parts of this quote appear to have been taken from comments he made during a talk about HIV testing using PCR in 1997. It’s not true that anyone can test for anything using PCR tests. Those designed to detect the virus that causes Covid-19 are highly specific.
PCR, or polymerase chain reaction, is a common scientific method where specific genetic material in a sample is replicated to the point that it becomes detectable. In the UK, PCR testing is currently mainly used to detect the Covid-19 virus in people who have symptoms. Dr Mullis invented this method, not Covid-19 PCR tests specifically, and died in 2019, before the pandemic. We have fact checked several false claims about Dr Mullis before.
Parts of the quote in the Facebook post seem to come from comments Dr Mullis made at an event held in Santa Monica in 1997, during a discussion about HIV and AIDS. Dr Mullis was an advocate of HIV/AIDS denialism, meaning he believed HIV doesn't cause AIDS, which has since been widely debunked as false.
When asked about using PCR to detect the HIV virus he said: “And with PCR, if you do it well, you can find almost anything in anybody.”
PCR Covid-19 tests are very sensitive, meaning that they rarely fail to detect the genetic material of the Covid-19 virus, if it is present. But they are also very specific, meaning they don’t often show false positives. They are the best test to find a current Covid-19 infection, according to the Royal College of Pathologists.
It’s worth noting that PCR testing has come a long way since 1983 when it was discovered, and since Dr Mullis made those comments in 1997.
Later on in the video, Dr Mullis says: “[PCR is] just a process that’s used to make a whole lot of something out of something. That’s what it is. It doesn’t tell you that you’re sick, it doesn’t tell you that the thing you’ve ended up with really was going to hurt you or anything like that.”
Although he wasn’t talking about Covid-19 testing, it’s true that PCR testing doesn’t necessarily tell you that you’re sick, just that the virus is present, as someone may test positive and not be showing symptoms, for example. Those people may still be able to pass on Covid-19, even if they’ve not got symptoms.
The Facebook post then says: “PCR tests use an amplified 40/45 cycles which give false positives..‘Medical Fraud’”.
These ‘cycles’ are the number of times the replication part of the PCR process is repeated, so that the specific genetic material, if present, can be detected. The cycle threshold is the number of cycles at which the virus is detected in the sample. The maximum number of cycles done may differ between labs because of how exactly they do PCR.
We’ve written about this several times before, but essentially cycle thresholds of 40 and 45 don’t show false positives, and aren’t evidence of medical fraud.
Public Health England says that, typically, a maximum of 40 cycles are conducted when testing for SARS-CoV-2 and at least one NHS trust has previously said it runs 45 cycles on its PCR tests. However, at higher cycles, PCR tests are more likely to detect people with low levels of the virus, which could indicate that they are early or late in their infection. This does not mean that the test result is invalid.
Image courtesy of CDC, via Unsplash.