For days there has been a debate 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 pandemic, the public should be aware that a positive PCR test does not have to be synonymous with disease or infectivity.

In order to get information about this, an anamnesis would have to be carried out after the test.

It would also help to take a look at the Ct value of the test result - as is sometimes done abroad.

The Ct value stands for the English term cycle threshold, in German: cycle threshold.

It shows how many cycles the PCR test went through before virus genetic material was detected.

If the amount of virus in the sample is large, relatively few rounds are sufficient.

The lower the viral load in the sample, the more cycles are necessary - and the higher the Ct value.

A positive test is not automatically a "new infection"

According to scientific studies, a risk of infection is as good as excluded from a value of around 30.

In view of the high sensitivity of the PCR test, it can work even when minimal virus residues appear, either at the beginning of an infection, but also while it subsides - up to many weeks afterwards and also in cases in which an infection was never noticed was.

It is accordingly misleading to call a positive PCR test a “new infection”.


There is hardly any debate in this country about the informative value of PCR testing.

Harvard epidemiologist Michael Mina wrote a few days ago on Twitter: “It's unbelievable that Ct values ​​are still rarely reported together with a positive SARS-CoV-2-PCR.

Often times, the only information a doctor or contact follower knows about a positive person is the Ct value.

The fact that we throw away Ct values ​​is remarkable. ”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 someone is. ”

In the Spanish capital Madrid, among other places, the authorities said they had contact with Mina and adjusted their handling of PCR results.

The regional government has been closely examining the Ct values ​​for months and is including them in decisions about tightening or relaxing measures;

Recently, the Ct value of the positive PCR tests was over 30 in around 50 percent of the cases.


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What does Christian Drosten say?

With regard to the informative value of PCR tests, what is interesting is what Christian Drosten, Charité chief virologist and advisor to the federal government, said in an interview with “Science” in May 2014.

At that time it was about the MERS virus, which also belongs to the coronavirus family and can cause severe inflammation of the respiratory tract and pneumonia.

At that time, Drosten was doing research on site in Saudi Arabia, where the MERS outbreak had occurred.


In the interview, he talked about the increased number of on-site tests - 459 across the country from January 1st to March 26th and then 4,629 in just one month.

“Something dramatic has changed, and that is the case definition,” said Drosten: “In the past, tests were carried out on patients who had pneumonia and needed intensive care.

But now people are being tested, not because they are sick, but because they have had contact with a patient.

Some of them have tested positive, but many of them don't really get sick. "

Drosten reports on six medical professionals who found a slight virus concentration in the throat via a PCR test: “That is difficult to interpret.

It is possible that these are infections that are quickly brought under control by the immune system, "says Drosten:" This can often happen with healthcare workers who deal with several really sick patients. "

Drosten reminds of the SARS pandemic in 2003. People who had contact with SARS patients but showed no symptoms “were not tested with PCR.

Instead, they were later tested for antibodies to see if an infection had occurred.

That should now also happen in Saudi Arabia.

Asymptomatic people should not be tested with PCR ”.

Politicians have made themselves comfortable


But that's not only happening in Germany in the Covid 19 pandemic on a large scale.

The Charité has not yet responded to the question sent last Sunday about the extent to which Drosten's assessment of PCR testing differs between MERS and Covid-19.

The fact is: In Germany, the Ct value hardly plays a role - and politicians are making no move to change anything.

The possible argument that it is too time-consuming and associated with too much bureaucracy to further examine those who have tested positive and to assess the number of cycles must not apply here.

Vaccines have been developed at rocket pace, hundreds of Covid research projects initiated and comprehensive compensation models developed for companies hit by lockdown.

There should also be more work with PCR possible.

Just: Does anyone want that?

The decision-makers have long since made themselves comfortable with their incidence values ​​and positive tests - a realistic overview of the disease process cannot be obtained this way.