Testing

The PCR test can be used to amplify specific DNA or RNA sequences outside the living organism. The genetic material of the virus is multiplied (amplified), which makes it possible to detect viruses even if the viral load is low.

The following components are required to carry out a PCR:

• examination material (e.g. tissue samples)
• specific reagents [nucleotides (DNA and RNA building blocks)] and laboratory equipment
• a detection system for the PCR products

The swab is usually taken from the nose or mouth. Genetic material (RNA) of the SARS-CoV-2 virus can be obtained from here. In the laboratory, the genetic material is amplified in several cycles. Afterwards, so-called fluorescent molecules are used, which attach themselves to the genetic material. This way, it can be determined whether the specific gene sequences of the virus are present or not. In addition, the viral load, i.e. the concentration of the viral genetic material, can be determined.

The CT value is a term often used in association with PCR tests. CT stands for Cycle Threshold and indicates the actual viral load in a given sample. It refers to the number of cycles that a real-time PCR has run before fluorescence, i.e. virus detection, is measurable. A high CT value indicates a low viral load in the sample. However, it doesn't necessarily reflect the infectiousness of the persons concerned.

To evaluate the PCR test, a lot of different information is needed, such as:

• the course of the disease
• the occurrence and nature of the symptoms
• possible contacts with infected persons
• staying in risk zones
• possible virus mutations

Further scientific data on PCR tests can be found on the following page: https://pubmed.ncbi.nlm.nih.gov/33595397/

A PCR test should be carried out whenever you

• show symptoms that could be related to a COVID-19 infection

The PCR test is carried out by qualified professionals in a designated facility. These include, for example, the various laboratories or hospitals. The National Health Laboratory (Laboratoire national de santé, LNS) also has the possibility of sequencing a sample to determine the type of coronavirus (mutation).

Only health care professionals or specially trained personnel can perform this test. 

The carrying out of this test (nasal or mouth swab) is limited to health care workers or specially trained personnel. In this case, a positive result should be considered as a suspicion of a COVID-19 infection and confirmed by a PCR test. In the case of a negative result, a high risk of infection can be ruled out at that time, but the result only serves as a momentary snapshot. Hygiene and protective measures must continue to be observed.

This test is intended for the rapid detection of an infected person in the presence of symptoms, but can also be used as a screening method, for example for visitors to a nursing home.

In the event of a positive test result, the person who carried out the test must report this to the Contact Tracing team using the form provided for this purpose.

This type of test can be carried out by any individual. It is intended to be used as a regular check, or to help in the rapid detection of a SARS-CoV-2 infection when symptoms occur. The positive result of an antigen self-test must be reported via this page.

Please note: Not every rapid test is approved as a self-test! A list of tests recommended as antigen self-tests in Luxembourg is available here.

An antigen self-test performed at school, sports or at work under the supervision of a person selected for this purpose must be reported via MyGuichet.

Important: Please refer to the provided package leaflet for detailed instructions before using the test. 

A few droplets of blood from the finger are used to analyse whether antibodies against the spike protein of the coronavirus (SARS-CoV-2) are present.

Positive test: The person has antibodies against the spike protein of the coronavirus, which means that either they have been in contact with the virus in the past or that the vaccine has caused an immune response. You could say that some protection has been built up. Scientifically, however, there is no limit above which one is considered protected. A high or low level of antibodies does not necessarily mean that you are immune, as antibodies are only a small part of the body's overall immune response.

Negative test: No antibodies against the spike protein are present at the time of testing. This can have different causes:

• You have never been in contact with the virus and you have not yet been vaccinated
• You have been vaccinated, but your body has no antibodies at the time of the test
  • The body has never developed antibodies and the vaccination has not triggered an immune response. You may be inadequately protected.
  • The body never developed antibodies but still responded well to the vaccination. Antibodies are only part of the overall immune response, and other parts of the immune system are quite active. Scientifically, this is considered proven, but such tests are not as easy to carry out as an antibody test.
  • The body has developed antibodies, but no longer produces antibodies at the time of the test due to lack of need. In this case, one can assume a certain protection because the body has built up its immune memory accordingly.

You can get tested to find out if you have developed antibodies. In general, vaccination is very effective and there is nothing to worry about. However, if you are considered vulnerable, or if you are taking immunosuppressants, it can still be interesting to get tested, as these people can receive another dose of the vaccine to boost their immune response.

The Health Directorate uses these tests to monitor the general situation in the country in order to get an overview of:

• how many people have been in contact with the virus or have been vaccinated
• how many people have developed a certain level of immunity, in order to be able to possibly adapt the general sanitary measures