Many people would like to be tested for antibodies. Is it that easy? Under which conditions? When is the virus tested at all? An overview.
Sore throat, cough, high temperature: Did I catch a cold shortly before the start of summer or did I get the coronavirus ? What about the serious infection that plagued me in February and tied me to my bed? In the end, was it Covid-19 and not the flu , as suspected at the time?
These are questions that concern many people these weeks, who feel sick or have been recently. A test could provide information. A basic distinction is made between tests for an existing infection and antibody tests that indicate a previous infection with the coronavirus .
An acute infection is usually a swab from the mouth, nose or throat detected. The Robert Koch Institute (RKI) now recommends testing all patients with respiratory diseases if there is sufficient capacity. A test is particularly urgent if someone has had contact with the infected person within the past 14 days, belongs to a risk group or works in a hospital or nursing home.
Covid-19 or flu? First clarify with a general practitioner
If you suffer from the typical flu symptoms such as sore throat, cough, runny nose, fever or even loss of smell and taste, it is best to call your doctor first and describe the symptoms; under no circumstances should you appear unannounced in practice. The team then discusses on the phone whether a test makes sense and where it is best to do it - this can be a special center, a clinic or a family practice.
Alternatively, you can also call the emergency medical service on 116 116. There you will be asked, among other things, about previous illnesses, age and complaints and receive an assessment based on this.
Test according to the PCR method if corona infection is suspected
If an infection with Sars-CoV-2 is suspected, testing is usually carried out using the PCR method . PCR is the abbreviation for the so-called polymerase chain reaction, which detects the genetic material of the coronavirus. For this, a smear is taken, whereby the RKI recommends two samples: one from the throat and one from the nose.
The samples are then examined in a laboratory. It usually takes a day or two to get a result. In the meantime, those affected should go into voluntary quarantine . There are also rapid tests , in which a result is already available after about two and a half hours. However, they are more expensive and are considered somewhat less reliable.
Antigen tests are another - still relatively new - method to detect an infection. Here, too, a smear is taken from the mouth, nose and throat. A test strip shows a result within 15 minutes. It is tested for protein building blocks of the pathogen (antigen) in the sample. So far, however, antigen tests have been considered less reliable than tests using the PCR method.
An antibody test can detect previous corona infection
A previous infection can be detected with an antibody test. Blood must be taken for this. Antibodies are proteins that the human immune system builds as a customized defense response when it has discovered pathogens in the body.
The antibodies are divided into classes that have different tasks and are produced at different speeds. The IgM antibodies, which are more responsible for the “rough”, are particularly quick to act. In the further course of the infection, the IgG antibodies, which have a more specific effect and remain in the blood for longer, then start.
The detection of antibodies is a complex process which requires several steps. In some cases, antibody tests can also reveal an existing Covid-19 disease. However, it takes a few days to two weeks after infection until the immune system has produced the various antibodies. Therefore, the tests do not work at an early stage of the disease and are not suitable as evidence of a current infection.
A corona antibody test is considered meaningful from the third week
From the third week on, an antibody test is considered meaningful. There should therefore be at least two weeks between the first symptoms (they usually only appear several days after the infection) and the blood collection. A procedure in which blood is drawn twice at intervals of seven to 14 days is also considered to be particularly accurate. Antibody tests are now offered by several manufacturers worldwide, their quality is different.
But uncertainties remain: It cannot be completely ruled out that an earlier infection with one of the more harmless corona cold viruses can lead to a false positive result . Antibodies also disappear from the blood over time in the case of infections that have occurred in the past. At the same time, this does not have to mean a decline in immunity: memory cells of the immune system can be able to quickly regenerate the corresponding antibodies if they come into contact with a pathogen again. How long the immunity lasts in the case of Sars-CoV-2 is not yet known.
Positive antibody detection could lead to false carelessness
The benefits of an antibody test for an individual are limited for all of these reasons: one knows with some - if not absolute - certainty whether one was infected with the corona virus and at least temporarily immune. What that means in concrete terms, how long you are immune afterwards and can no longer be infected, is not clear . Therefore, positive antibody detection could lead to false carelessness.
Antibody tests for a large number of people are nevertheless very informative for science . Because they provide an indication of the proportion of those in the population who have already come into contact with Sars-CoV-2.
Experts advise against corona self-tests
The health insurance companies always pay for tests if they have been prescribed by a doctor. This applies to tests for acute infection as well as to corona antibody tests . Tests for self-payers are increasingly being offered on the Internet, where you have to take a throat smear yourself or take blood from your finger and then send in the samples.
However, experts advise against such self-tests , as poor quality of the sample taken or improper transport could falsify the result.