Corona self-tests: how does the nasal swab work?
Maximilian Reindl studied chemistry and biochemistry at the LMU in Munich and has been a member of the editorial team since December 2020. He will familiarize himself with medical, scientific and health policy topics for you in order to make them understandable and comprehensible.
More posts by Maximilian Reindl All content is checked by medical journalists.Corona tests for personal use are becoming increasingly popular among the population. You can uncover inconspicuous Sars-CoV-2 infections and make a significant contribution to containing the corona pandemic. The majority of the self-tests available on the market rely on sampling by means of a nasal swab. Read here how these self-tests are used and which ones are available.
What do I have to consider when testing?
The vast majority of available corona self-tests rely on taking samples by means of a nasal swab. This can be used to detect coronaviruses that are located in the upper nasopharyngeal tract or in the upper respiratory secretions.
Please note: The so-called viral load can vary depending on the stage of infection. This means that if you are infected with Sars-CoV-2, the amount of (detectable) virus will fluctuate over the course of the disease.
In certain time windows of the infection, this amount of virus can also be below the detection limit - especially on the first day after an infection. However, it can also happen that the test does not work, although the amount of virus is sufficient. In both cases you will get a false negative result.
Despite the negative test result, you are infected and thus contagious. It is therefore important that you continue to observe the distance and hygiene rules even with a negative test result, in order not to unnecessarily endanger your fellow human beings.
You can only be certain whether you are infected with Sars-CoV-2 or not through an official PCR test carried out by a certified laboratory.
How do the nasal swab tests work?
Corona self-tests using a nasal swab are antigen tests that detect the Sars-CoV-2 pathogen. They are used for acute diagnosis - that is, they provide a “snapshot” of your state of infection.
Corona self-tests for nasal swabs usually contain the following items:
- Coronavirus test cassette
- Sample tubes and extraction buffer
- sterile test stick or cotton swab
- Detailed instructions
Also check whether the test has a CE mark.
These antigen tests target a special biological structure of the Sars-CoV-2 pathogen: the so-called nucleocapsid. This viral protein structure is only formed when the virus multiplies (replicates) in your body. It is the same for all variants of the Sars-CoV-2 pathogen.
If your nasal swab contains the coronavirus, a line will appear in a window of the test.
The antigen self-tests are not to be confused with the antibody self-tests, which are also offered. The latter can also strike later in the course of an infection, when antibodies have already formed. As a rule, however, they are used to detect infections that have already been overcome, as well as a corresponding immune protection.
How do you take the test?
Rapid antigen tests using a nasal swab can also be carried out safely and easily by laypeople.
Read instructions
Read the enclosed instructions carefully. The tests are basically structured in a similar way. However, their application differs in detail from manufacturer to manufacturer. In order for the test to work reliably, you must carefully follow the manufacturer's instructions.
Prepare
Blow your nose so that more secretion gets to the front of the nose.
Take a sample
Then take the sample. This is done with a cotton swab that you insert about two to three centimeters into your nose and wipe on the front edge of the inside of your nose. Usually three to four times, in one or both nostrils.
Put the sample in the solution
The manufacturer usually supplies a small sample tube. This contains a so-called "extraction buffer". After taking the sample, stick your cotton swab into this. This is how you transfer any virus particles that may be present into the buffer liquid.
In most cases, the supplied sample tube works similarly to a "pipette". In this way, you can precisely dose the specified amounts of this sample solution.
Add sample solution to the test cassette
You put a few drops (usually 1 to a maximum of 3) from the sample tube into the marked test field of the test cassette.Now you have to wait for the specified time (usually 15 to 20 minutes) after which an (enzymatic) reaction delivers the result.
Read the result
Similar to a pregnancy test, you can read the result from lines that appear in a window of the test kit.
One is for control. It shows whether the test is functional. If it does not appear, the test is considered invalid and must be discarded. If the control line appears, there are two options:
- If only the control line appears, the test is negative. You are unlikely to be contagious at the time of testing.
- If the second line also appears, the test is positive. This means that there is a high probability that you are carrying the coronavirus.
Where can I get the Corona self-tests?
Corona self-tests can be obtained in different ways: Either you order them on the Internet (online pharmacy) or you can obtain them in brick-and-mortar stores (pharmacies, drugstores, supermarkets).
The extent to which the respective models are in stock and available depends largely on the respective provider.
Which corona self-tests are there?
The Federal Institute for Drugs and Medical Devices (BfArM) in Germany maintains and updates a current list of the available corona self-tests (nasal swabs).
Please note that all information (if available) on the specificity, sensitivity and duration of the tests originate from the manufacturer and has usually not been verified by an independent body.
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