Corona self-test for at home: How reliable is it?
Corona tests for at home have recently been available. But how reliable is such a self-test? This has not yet been adequately investigated.
Recently, pharmacies, but also the Austrian drugstore chains DM and BIPA, have been offering corona tests from various manufacturers for at home. Whereby “at home” only refers to taking the sample:
According to the instructions, a special solution is used to gargle or saliva is collected in a tube. Everything is then well packaged and sent to the laboratory by post. The price of the do-it-yourself tests is between 120 and 150 euros. So much like a professional corona test, which you can have carried out in a laboratory if you wish.
Can you rely on the result for this? Absolutely, my manufacturer. A laboratory whose self-test was available at the DM drugstore for at least a while even certifies its product to be 100 percent accurate.
Absolute certainty – is that even possible? We did the fact check. And came across many open questions.
Do-it-yourself tests: Studies are thin
We couldn’t find any studies that examined how reliable corona self-tests are for at home compared to professionally conducted tests. The manufacturers of the self-tests available in Austria could not send us any studies on the accuracy of their products on request.
In tests such as the corona self-test, most errors are likely to occur when the sample is taken  . The collection of saliva or gargle solution or the nasopharynx smear is prone to errors. Especially with this crucial part of the self-test, the user is left to his own devices at home.
Another uncertainty factor is the dispatch of the sample to the laboratory: Long transport times or heat, for example, could falsify the samples and thus the result.
However, this has not yet been scientifically investigated. It therefore remains unclear whether the do-it-yourself version of the corona test is just as good as the professionally carried out test directly in the laboratory or in the doctor’s office.
Throat swab single-handedly? Seems doable
The self-tests currently available in Austria require a long gargle or a few amounts of saliva. In other countries there are self-tests in which the samples are collected by swabbing the throat.
An Australian research team wanted to know how well this works : In several outpatient clinics, test subjects first took a smear themselves, following written instructions. They had to tickle their throat and nose with a cotton swab, so to speak. Then the same procedure took place again, this time, however, by trained health personnel.
The comparison showed: laypeople and professionals were equally successful – there were almost no differences in the test results.
The Australian study took place directly in health care facilities. The difference to the self-tests in this country: The samples were not sent to the laboratory by post. So this uncertainty factor was not examined.
No test is infallible
Whether at home or in the doctor’s office: No test is absolutely error-free. This also applies if the sample is taken by trained personnel and analyzed in the laboratory without delay.
The analysis of samples using PCR (polymerase chain reaction) is currently the most reliable way to determine an infection with the coronavirus. The virus can be detected directly in the laboratory using PCR. All you need is a sample of the virus you are looking for – mostly saliva, nasopharyngeal secretions or coughing.
The test result is fairly certain . If 100 infected people perform a PCR test, the test will correctly identify the infection in an average of 89. He certified 11 people in the best of health despite the virus. Experts would say: the sensitivity of the PCR test is around 89 percent.
We need even better studies to verify this preliminary finding. But what they show: false results are possible and infections can be overlooked.
Corona self-test: Does it have any advantages?
Despite all the uncertainties: taking the corona test into your own hands also has advantages. Sometimes it can be an inhibition threshold to dial the hotline 1450 in Austria or to seek medical help if you suspect an infection. Ordering the test on the Internet or buying it from a pharmacy could facilitate quick access to certainty.
On the other hand, self-tests at home can relieve the health system and its staff.
Self-test: Not officially recognized
Anyone who buys a self-test for at home should know: The result is intended for personal information. It is not recognized by the Austrian authorities. So if you want a test for entry into the country or as a replacement for a mandatory quarantine, you still have to contact an official body or in Austria the hotline 1450.
If a laboratory detects an infection with the coronavirus, it is obliged to report this to the health department immediately – even if self-tests are carried out at home.
In the right time…
Samples from infected people can also give negative results. The problem is usually not the laboratory analysis, but the examined material.
A summary of studies has shown: The coronavirus is likely to be found most reliably in the cough, the so-called sputum. Throat swabs and saliva are likely to work a little less reliably.
… in the right place?
But not only the type of sample material or its correct extraction determine the reliability of the result. The timing is also important. On the third day after the onset of symptoms, the PCR test seems to be the most reliable way to detect an infection. A test carried out too early or too late can, however, drastically lose its informative value .
An example: Anyone who has had contact with a sick person and tests the next day is very likely to receive an inconspicuous result – even if an infection has occurred.
In general, if there is a high suspicion of an infection or symptoms persist, a single, inconspicuous test result cannot be trusted. In this case, the test should be repeated about a day or two later.