An Overview of Corona Tests
Since the start of the pandemic, the search for a vaccine against the coronavirus has been intense. At the same time, scientists worked on finding ways to detect the virus in order to break the chain of infections. Currently, there are three test methods available that provide important and reliable information if they are used correctly.
On this page, we want to give an overview of the tests, when they should be used and what their results mean.
PCR stands for polymerase chain reaction and describes a test method in which precisely defined DNA sections of the SARS-CoV-2 virus are amplified with help of a special enzyme. They can then be detected using a special device. The PCR method allows the medical professional to detect the presence of the SARS-CoV-2 virus in the swab and to make a statement about the viral load.
While the antigen test also directly detects SARS-CoV-2, it only detects a specific surface protein of the virus. In contrast to the PCR test, the antigen test can be performed on site and delivers results within a few minutes. Its main advantage is the uncomplicated test procedure and quick results, which means that the medical professional can immediately decide how to proceed.
The antibody test differs from the PCR and antibody test, as it does not detect the virus itself. The antibody test detects the body’s immune reaction to a SARS-CoV-2 infection. Since the formation of antibodies does not begin until a few days after infection - maybe even later - it is not suitable for detecting an acute infection. As a result, it is used to determine whether a patient has already been infected with SARS-CoV-2.
NAb Rapid Test
This form of the rapid test detects neutralising antibodies and therefore also an immune reaction of the body to the pathogen SARS-CoV-2. This neutralisation test can be used to determine whether a COVID-19 vaccination was successful or whether the patient has potential immunity after having been infected with SARS-CoV-2.
A Direct Comparison between the Test Methods
|PCR Test||Antigen Test||Antibody Test|
|What is detected?||Genetic virus material||Protein fragments of the virus||Antibodies against the virus|
|Direct pathogen detection||Direct pathogen detection||Immune reaction of the patient|
|In which stage of the infection can the test be used?||During an acute infection||During an acute infection||In the late stage of an infection or when the infection is already over|
|Which sample material is used?||Nose/throat swabs||Depending on the test: ||Blood sample|
|Where is the test performed?||In the lab||At the point of care (e.g. in the surgery, hospital or outpatient department)||At the point of care (e.g. in the surgery, hospital or outpatient department)|
|How long does it take to read the results?||24 - 48 hours (incl. transport of the specimens to the lab)||Approx. 15 - 30 minutes||Approx. 10 - 20 minutes |
|Why is the test performed?||To confirm a suspected diagnosis||To test the people who came into contact with the virus, to identify patients that are infectious but don't show any symptoms ||To detect the past occurrence of an infection|
All SARS-CoV-2 antigen rapid tests listed here are BfArM-listed* (German Federal Institute for Drugs and Medical Devices).
*with the exception of the Beright Antigen Test
Antigen Rapid Test
This rapid corona test confirms an acute infection by direct pathogen detection. The SARS-CoV-2 test is carried out with sample material from nasopharyngeal swabs and can be directly performed at the point of care (e.g. in the surgery or hospital).
The test kit includes a sterile swab, an extraction buffer and a test cassette. The principle and procedure for the different antigen tests are generally very similar and their major difference lies in the specificity and sensitivity as well as the amount of work involved in carrying out the test. Additionally, there are rapid tests that are carried out with saliva. These tests are particularly suitable for patients who do not tolerate swab tests well - such as small children, people with disabilities or elderly patients.
The NADAL COVID-19 antigen test from the German manufacturer nal von minden enables a particularly uncomplicated test procedure and provides a reliable test result in only 15 minutes due to its high specificity and high sensitivity. In addition, the test is listed with the BfArM (German Federal Institute for Drugs and Medical Devices).
The greatest potential of the antigen tests lies with the rapid identification of infected patients who do not show any COVID-19 symptoms, but who have had contact with people who are known to be infected. The test allows for a quick assessment of the status of infection and prevents an unnoticed COVID-19 infection from causing a strong spread of the virus.
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Antibody Rapid Test
This rapid test can be used to identify patients who have already produced antibodies against SARS-CoV-2. It not only plays a role in the identification of infection chains, but may also be of interest for patients who are in a late stage of infection. In a later stage, the pathogens are often no longer detectable in the nasopharyngeal cavity. Unlike other corona tests, this kind of rapid test is carried out with a blood sample.
A negative result of the rapid antibody test does not rule out an acute infection. It only means that there has not (yet) been an immune reaction. Such an immune response and the formation if IgG and IgM antibodies can be expected after a few days at the earliest – in most patients it takes even longer.
Therefore, this coronavirus test is not suitable for detecting a current infection with the novel coronavirus.
As with the antigen test, the antibody tests from the different manufacturers are very similar in terms of the test procedure and the test principle. In addition to the test cassette, the kit contains a pipette for handling the blood sample and buffer solution.
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Nab Rapid Tests
The neutralisation test is also considered an indirect virus detection test. It determines the neutralising antibodies (NAb), which are a late immune response of the body to the pathogen SARS-CoV-2.
Neutralising antibodies (NAb) are a subtype of antibodies that can inhibit viral entry into the cell and viral replication. In the specific case of Corona, they inhibit the binding of the spike protein to the ACE2 receptor and deny the SARS-CoV-2 virus cellular infiltration.
NAb rapid tests can therefore be used to determine whether a patient has potential immunity after having had an infection or whether a full COVID-19 vaccination has been successful.
The execution of neutralisation tests differs in a few points from the execution of the rapid tests mentioned above. The test cassettes used in this rapid test have a well for the sample material (serum, plasma or whole blood samples) and a well for the specific buffer solution. The two liquids are applied separately and are not mixed.