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Ct value: We need to evaluate the results of the PCR tests more accurately

Ct value: We need to evaluate the results of the PCR tests more accurately

Opinion Controversy over the value of Ct

We need to take a closer look at the results of the PCR tests

The new Rapid PCR Test has this feature over all the others

Samples are taken easily and painlessly using the gargle test at 500 testing centers across Germany. Evaluation should be available within 24 hours and considered more reliable compared to rapid tests.

A positive PCR test is not synonymous with corona disease, nor is it an infection. Another more important value. Politicians in Spain react to these findings – but in Germany hardly anyone wants to lead the debate.

sFor days there has been discussion about linking measures to incidence values. The problem lies much deeper: With the PCR tests themselves, more than a year after the start of the epidemic, the public should realize that a positive PCR test does not have to be synonymous with disease or infection. In order to obtain information on this, precedents must be made after the test. It’s also helpful to take a look at the Ct value of the test result – as it sometimes does on the outside.

The value of Ct denotes the course limit of the English term, in German: course threshold. It shows how many cycles a PCR test went through before the virus’s genetic material was detected. If the amount of virus in the sample is large, then a relatively small number of rounds will suffice. The lower the viral load in the sample, the more cycles necessary – and the higher the Ct value.

A positive test is not automatically considered a “new infection”

According to scientific studies, the risk of infection is as good as it is excluded from a value of about 30. Due to the high sensitivity of the PCR test, it can work even if the minimum amount of virus residue appears, either at the beginning of the infection or even as it recedes – for several Weeks afterward and also in cases where the infection was never noticed. Consequently, it is misleading to call a positive PCR test a “novel infection”.

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Matthew Floriani has been the Head of Laboratories Group Synlab since April 2018. Former McKinsey consultant worked at the French oil company Total and the German logistics company DHL

There is hardly any discussion in this country about the informational value of the PCR test. The Harvard University Epidemiology Michael Mina He wrote a few days ago on Twitter: “It is unbelievable that Ct values ​​are rarely reported alongside positive Sars-CoV-2-PCR. Often times, the Ct value is the only information a doctor knows or follows about a person Positive. The fact that we are discarding Ct’s values ​​is amazing. ”In an interview with Science magazine, he said,“ We ​​have to stop thinking that someone is positive or negative, but rather ask ourselves how positive this person is. ”

Among other things in The Spanish capital, Madrid Authorities said they contacted Muna and modified how she handled the PCR results. The regional government has been closely studying Ct values ​​for months and is including them in decisions regarding tightening or easing measures; Recently, the Ct value for positive PCR tests was more than 30 in about 50 percent of cases.

What does Christian Drosten say?

In terms of the informational value of PCR tests, what is interesting is what Christian Drosten, the chief virologist Bashariti and advisor to the federal government, said in an interview with Science in May 2014. At the time, it was about the Mers virus, which also belongs To the coronavirus family and can cause severe respiratory infection and pneumonia. At the time, Dorsten was researching a site in Saudi Arabia where the Mers outbreak had occurred.

In the interview, he talked about increasing the number of on-site tests – 459 across the country from January 1 to March 26 and then 4,629 in just one month. “Something dramatic has changed, and that’s the definition of the situation,” said Drosten. In the past, tests were performed on patients with pneumonia who required intensive care. But people are now being tested, not because they are sick, but because they have been in contact with a patient. Some of them have tested positive, but many of them don’t really get sick. “

Drosten reported that six medical professionals found a slight concentration of the virus in the throat using the PCR test. “It’s difficult to explain. This is likely an infection that is quickly controlled by the immune system,” says Drosten. “This can often happen with healthcare workers who deal with many really sick patients.”

Drosten mentions the SARS pandemic in 2003. People who had been in contact with SARS patients but had no symptoms “were not tested with PCR. Instead, they were subsequently tested for antibodies to see if the infection had occurred. They should This is also happening now in Saudi Arabia. People who do not have symptoms should not be tested for PCR. “

Politicians made themselves comfortable

But this is exactly what is happening on a large scale not only in Germany in the shadow of the Covid-19 pandemic. Charité has yet to respond to the question sent last Sunday about how different the Drosten PCR test is between Mers and Covid-19.

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Leadership: Health Minister Jens Spahn (left) and Chancellor Angela Merkel

The truth is: in Germany, the Ct value hardly plays a role – and politicians do not take any step to change anything. The potential argument that it takes a long time and involves a lot of bureaucracy to conduct further examination should not apply to those who test positive and to assess the number of cycles. Vaccines are developing at a rocketing pace, hundreds of Covid research projects and comprehensive compensation models have begun for companies hit by the lockdown. There should be more PCR work possible.

Only: Does anyone want that? Decision makers have long felt comfortable with their decisions Injury values ​​and positive tests It is not possible to obtain a realistic overview of the disease process in this way.

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