An article shared on social media falsely claimed that the World Health Organization (WHO) had acknowledged that the number of COVID-19 cases was “meaningless” due to “invalid” PCR tests. The WHO told Reuters this claim was not true.
The article was originally posted on GlobalResearch.ca (here), a website that describes itself as a Montreal-based research and media organization that publishes the ‘unspoken truth’ (www.globalresearch.ca/about-2). The headline, the screenshot of which has been repeatedly shared on Facebook (here, here, here, here, here, here), reads: ‘The WHO confirms that the Covid-19 PCR test is incorrect: estimates of’ positive cases’ are Meaningless . The conclusion has no scientific basis. ”
‘The World Health Organization (WHO) one year later tacitly admits that ALL PCR tests performed at a gain threshold of 35 cycles (Ct) or higher are INVALID. But this is what they recommended in January 2020, in consultation with the virology team at the Charité Hospital in Berlin, ”reads the broader article.
If the test is performed with a threshold of 35 cents or higher (recommended by the WHO), segments of the SARS-CoV-2 virus cannot be detected, which means that ALL the so-called confirmed ‘positive cases’ ‘which has been invalid for the past 14 months. ”
In support of this claim, the author then points out what he says is a ‘withdrawal’ that the WHO released in January (here).
However, this is not true. The WTO information notice is not a withdrawal; rather, it is an explanation for laboratory professionals on how to interpret PCR results. It does not mention anything about the “35 cycle gain threshold”, nor does it say that PCR test results are invalid.
The WHO said in an email to Reuters in February: ‘Since the beginning of 2020, the WHO has received ten reports of problems related to PCR tests for the detection of SARS-CoV-2 (the virus that causes COVID- 19), including some products listed by the WHO for emergency use. The reports were for misdiagnosis, both false positive and false negative results.
“After thorough investigation, WHO has confirmed that tests are not always used appropriately and according to the manufacturer’s instructions. In particular, users in laboratories experienced problems with these tests when they did not apply the recommended positivity threshold. This can lead to false negative results (if the threshold is lower) or false positives (if the threshold is higher). “
PCR stands for Polymerase Chain Reaction, a process that is repeated repeatedly to amplify genetic material of the virus in a sample. Scientists regularly run between 40 and 50 cycles of the process, depending on the laboratory and the test kit (here,here).
Ian M. Mackay, a virologist and deputy professor at the University of Queensland in Australia, told Reuters in February that reducing the cycle count (as suggested in the article) would change almost nothing. In other words, a large majority of the results will still be returned as positive and included in the case.
“This is because most PCR results do not drop more than 40 cycles – the usual end point of a real-time PCR,” Mackay said. “They fall on a much earlier cycle number.” This is explained in more detailhereand in another Reuters here on the subject.
The threshold cycle refers to a specific point in the test where the positive result occurs, Mackay explained. At that point, the fluorescence signal of the PCR test crosses a certain threshold, which can be determined by the user or the manufacturer of the test. The value can be determined or adjusted by the user. ‘The WHO says that if the manufacturer has defined a value, but if you would prefer to adjust the setting, do not do it – stick to what the manufacturer said because they did the previous job to get the best value for determining threshold, ”Mackay said.
The WHO added: ‘We have seen a small number of cases where users did not follow the instructions to the letter. Millions of PCR tests have been properly performed with accurate results. ”
VERDICT
Untrue. The World Health Organization has not issued any withdrawal on PCR tests to say that all positive results are invalid; rather, the organization issued an explanation to professional scientists recommending them to follow instructions from test manufacturers.
This article was produced by the Reuters Fact Check team. Read more about our fact-checking work here.