PCR tests: skewed comparisons and false statements

The forthcoming prioritization of the PCR tests is causing discussions: numerous false claims are made when comparing with Austria. In addition, the benefit of many PCR tests is controversial.

Since the federal and state governments decided to prioritize PCR tests in Germany in the future, a heated argument has broken out: individual groups such as teachers feel ignored, and it is also completely unclear so far how the rules should be implemented.

The Federal Ministry of Health was also able to do this ARD fact finder no information on this so far. When asked, it was said that “no details can be given at the moment”. However, it is “not about restricting the claim, but prioritizing the test execution if the capacity limits are reached. There is therefore no reason to be concerned,” according to the ministry.

We sometimes test differently abroad

Meanwhile, other countries are taking a different approach: Austria in particular is the focus, because in the provincial capital of Vienna, all citizens can be tested daily with PCR free of charge.

The participants’ throat tests are first “pooled” – that is, ten samples are initially poured together, with a reserve quantity being retained. Then a PCR test is performed. Only if this is positive are the respective samples individually examined again to determine who exactly is positive.

Numerous false claims from Germany

The Viennese publicist Natascha Strobl collected false statements from German politicians, official spokesmen and media representatives on Twitter:

This is what Hamburg’s first mayor, Peter Tschentscher, claimed in NDR, in Vienna “PCR diagnostics would not be organized via professional laboratories, but via drugstores and similar providers”. This is not possible due to the strict German regulations. But this statement is wrong: Although the PCR tests can be given in supermarkets and drugstores, among other things, they are examined just as professionally in a laboratory as in this country. The low-threshold offer is considered exemplary.

Also in the public event and documentation channel Phoenix reported moderator Erhard Scherfer that the Vienna PCR tests were “not examined in laboratories, but in a different, somewhat simpler way” and were “a mixture of a rapid test and a PCR test”. This claim is also demonstrably false. Scherfer thanked Twitter for the tip and said he would always use two sources in the future, it was “a lesson” for him.

Scherfer’s source, however, was reputable, but still wrong: Because the chairman of the professional association of German laboratory doctors, Andreas Bobrowski, had told the “Tagesspiegel” that it was “in Vienna only so-called point-of-care tests (POC) that are not in laboratories, but would be “evaluated by machine right away on site”. “The results obtained are significantly less reliable, their accuracy somewhere between rapid tests and real PCR tests,” quoted the Bobrowski newspaper. But the gargle tests are not POC tests, they go to the laboratory.

When the freelance journalist Tilo Jung questioned the spokesman for the Ministry of Health, Oliver Ewald, at the federal press conference, he replied that the “PCR lollipop tests in Austria” had “insufficient significance” and were therefore “not intended for Germany”. This statement is also not scientifically tenable. Although the sensitivity of pool tests according to studies slightly reduced, but the results can be used reliably. In addition, in Vienna it is not a lollipop but a gargle test.

Apples and pears comparisons?

Conversely, however, it is also questionable to simply compare the number of pooled PCR tests with the number of individual tests. For example, the magazine “Katapult” on Twitter stated that Vienna’s daily test capacity was 800,000, while in Germany it was only 394,000. In addition, the tests in Vienna are free, while in Germany they cost 49 to 69 euros.

However, this comparison is flawed in that Vienna does not carry out 800,000 individual PCR tests, but always ten samples at the same time. Theoretically, up to 800,000 people can be tested in this way – but only as long as the positive rate does not skyrocket. Because if too many of the pools are positive, a corresponding number of individual follow-up tests must be carried out. So became according to the Viennese magazine “Falter”, which reported in detail on the evaluation of the throat tests in December, temporarily reduced the pools to five so as not to have to retest too often. This in turn limits the capacity.

As far as the costs are concerned, some incorrect figures are compared. The Viennese do not pay individually for their test, but the state – and thus the taxpayers – does. Anyone who has a positive rapid test or symptoms is also free of charge in Germany for a PCR test.

The Viennese provider “Lead Horizon” charges six euros per sample. That means each pool with ten samples costs 60 euros. In Germany, the laboratories receive 35 euros from the health insurance companies for each PCR test. However, the laboratory effort for a pool test is also somewhat higher. From the laboratory’s point of view, the pool tests also pay off above all if there are no mass re-tests of positive pools.

Laboratories defend German model

The chairman of the Accredited Laboratories in Medicine (ALM) in Germany, Michael Müller, points out in an interview with the ARD fact finder pointed out that the German laboratories maintained their capacities in the summer when they were hardly used. If politicians wanted higher capacities, they would have to take the risk with the financing in the event that the capacities then built up are not used. In addition, the specialists required for the expansion are simply “not so easily available”.

Müller also notes that the benefit is questionable: “The measured incidences in Austria are in the range of Germany or higher and in Vienna run parallel to the rest of the country – currently even well above the national average. So I should ask myself what I’m achieving due to the cost-intensive capacities and we really need them in Germany,” says Müller.

Similar to Federal Health Minister Karl Lauterbach, Müller also considers the rapid antigen tests that are widespread in Germany to be a very suitable means – especially in times of high incidence. “We are currently confirming around 85 percent of all positive rapid tests with PCR, which is to be expected given the infection process with many infected people,” says Müller. In summer, when the virus spread less, this number was significantly lower. “This means that anyone who is currently testing positive with a rapid test is very likely to actually be positive.” Lauterbach had also advocated this.

How meaningful is the incidence in the future?

However, there is concern about how meaningfully the incidence can be measured in the future. The data journalist Claus Hesseling, who for the NDR Evaluating corona numbers drew attention to this on Tuesday: “If only certain groups receive a PCR test, it means that the incidence curves will greatly underestimate the course of the pandemic,” said Hesseling.

The Federal Ministry of Health was also able to answer the question of how the incidence should be determined exactly in the future ARD fact finder not provide any information so far.