We are searching data for your request:
Upon completion, a link will appear to access the found materials.
Corona Tests: How Safe Are They Really?
According to experts, the number of corona tests in Germany has increased significantly. The Federal Ministry of the Interior proposed weeks ago in a strategy paper to test a lot more. But how safe can the tests indicate an infection?
How many people in this country have already been infected with the SARS-CoV-2 coronavirus and are - most likely at least - immune? This question is exciting, but not easy to answer: the analyzes are tricky.
High number of unreported cases
Many people look at the number of people infected with corona. But it is also clear that there is a significant number of unreported cases.
Studies in several regions of Germany should provide a better overview. An antibody test is now coming from the Roche biotechnology center in Penzberg, Upper Bavaria, which, according to Chairman of the Board of Directors, Christoph Franz, is supposed to clarify millions of times worldwide.
But because there is no 100% reliable test in all respects, the results of such examinations are questionable. "There is a large gray area," says Antonia Zapf from the Institute for Medical Biometry and Epidemiology at the University Medical Center Hamburg-Eppendorf.
So far, the numbers and studies have given a good impression of the development. "But it is important to communicate that they are estimates - not the truth."
What specificity and sensitivity say about a test
Manufacturers indicate how reliably a test works with values for specificity and sensitivity. The sensitivity stands for the detection rate, i.e. the percentage of those affected by whom the infection is actually recognized.
A test with a sensitivity of 95 percent identified 95 out of 100 infections and five did not. According to the company, the sensitivity for the Roche test Elecsys Anti-Sars-CoV-2 is 100 percent. Chairman of the Board of Directors Franz spoke of a completely "new level of quality".
The specificity states how many healthy people who are definitely not or were not infected with the virus are actually recognized by the test as healthy. A test with a specificity of 95 percent incorrectly gives a positive result in five out of 100 non-infected people.
Roche specifies the specificity for Elecsys Anti-Sars-CoV-2 at 99.8 percent. With high sensitivity and low specificity, there can be many false positive results.
A distinction must also be made in the tests as to whether it is a detection of the genetic material of the Sars-CoV-2 virus or an examination for special antibodies that the person concerned developed after infection with this virus.
According to the Robert Koch Institute (RKI), the coronavirus for current infections is detected on a molecular biological basis by looking for the genetic makeup of the virus in a throat swab (RT-PCR).
Different test systems in the laboratories
"So far, several different test systems have been developed, each of which recognizes certain gene segments of the pathogen," explains the Bavarian State Office for Health and Food Safety (LGL).
Specificity and sensitivity depended, among other things, on the gene segment used or the combination of gene segments - but also on the RT-PCR reagents used, according to the LGL. Laboratories therefore work with different test systems and independently procure the materials required for this.
Tests for SARS-CoV-2-specific antibodies in the blood as well as Roches Elecsys anti-SARS-CoV-2 play no role in the diagnosis of an acute infection, as RKI reports that about seven days between the onset of symptoms and the detectability of specific antibodies pass, in individual cases more.
The decisive factor is the distance between the illness and the test, as Zapf also explains. The longer this period of time, the less likely the RT-PCR is positive - and the greater the likelihood that the antibody test will be positive.
It becomes problematic with so-called false positive or false negative results. Simply put: if the displayed result does not correspond to the facts. The consequences differ depending on whether it is a virus detection using RT-PCR or an antibody detection.
Wrong results and their consequences
In the case of RT-PCR, false-negative results are particularly fatal, says Zapf, since this means that the test persons are classified as healthy even though they are infected. The professor makes it clear: "That means that people go out and maybe infect others."
In the case of false positive tests, people and contact persons would have to be in quarantine, which would actually be unnecessary. But in case of doubt, this is the lower damage for the whole society.
In contrast, the consequences of a false positive result are more serious in your opinion in the antibody test, as this makes people feel wrongly wrong and may no longer adhere to hygiene regulations and contact restrictions, for example.
Here is a calculation example: Let us assume that out of 83 million people in Germany one million would be infected and one million would be healthy again and would have developed antibodies. A full survey with tests (RT-PCR and antibody test) with a sensitivity and specificity of 95 percent each would misdiagnose 50,000 infected as still healthy and 50,000 mistakenly as healthy.
In turn, more than four million people would get a false positive result - so they think they are infected even though they are healthy. And the antibody test would lead to over four million false negative results.
In addition, according to the Paul Ehrlich Institute (PEI) as the Federal Institute for Vaccines and Biomedical Medicines, manufacturers can still certify Covid 19 tests until May 2022.
The authority can therefore make no statement about the reliability of rapid tests, "since corresponding studies have not yet been carried out". The COVID-19 antibody test also had to rule out a possible cross-reaction with antibodies that were raised against other corona viruses.
The institute also points out that the validation of tests that are offered on the Internet, for example, is not always guaranteed due to the existing possibility of "self-certification". "There is evidence that there are also counterfeits of certificates." (Ad; source: dpa)
