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Coronavirus: According to researchers, rapid antigen tests are less reliable than assumed

Munich. German researchers warn: The widely used corona rapid tests are less reliable than assumed. The sensitivity of these antigen tests is sometimes lower than specified by manufacturers, emphasizes the National Research Network University Medicine on Covid-19 in a position paper. The doctors expressly warn against loosening hygiene rules in old people's and nursing homes, in which rapid tests are used.

In contrast to the particularly reliable PCR tests, rapid antigen tests do not detect the pathogen on the basis of its genetic make-up, but on the basis of certain virus proteins called antigens that appear on the virus surface. If the antigens appear in the test, then Sars-CoV-2 rages in the body: The person is at the peak of the infection and most contagious. People who have not yet broken out of Covid-19 fall under the radar of the method.

Two Munich university hospitals checked the quality of the antigen tests on 859 smears. Qualified staff carried them out. The rapid test most commonly used in Germany and a second product were put to the test.

No charter

"Only six out of ten Sars-CoV-2 infections are recognized," says Oliver Keppler, head of virology at the Max Pettenkofer Institute at Munich's Ludwig Maximilians University. "On the other hand, two out of 100 uninfected people also receive a false-positive result."

In the emergency department of the Stuttgart Katharinenhospital, 459 patients were also tested with two different methods and here, too, the reliability of the rapid antigen tests was worse than that of the PCR method, especially in patients without symptoms.

Rapid antigen tests could mostly detect "highly infectious people with high viral loads," explains Keppler. "However, it is not the case that an infection can be reliably ruled out by the negative result of a rapid test. A negative rapid antigen test is not a free ticket."

"In the last few weeks we have seen outbreak scenarios in which incorrect results from rapid antigen tests probably played a decisive role in the entry of the virus," emphasizes Keppler: Even after a negative rapid test result, one must comply with the hygiene rules (est / dpa )