Practical information about testing
Practical information about testing can be found at Government.nl. If you have symptoms, you can make an appointment to get tested. You can also be tested if you were in close contact with someone who tested positive for COVID-19, even if you do not have symptoms. There are also other exceptions in which testing without symptoms is possible. The same website also contains information about the test results.
Why is testing important?
It is important for people to get tested if they have symptoms. This ensures that new infections will be detected sooner. People who do turn out to have the virus will go into isolation and stay home. The Municipal Public Health Services (GGDs) start source and contact tracing and give household members and close contacts advice on what they should do. Quarantine applies if household members and close contacts are not fully vaccinated, and/or have not had a COVID-19 infection in the past 6 months. This helps prevent them from infecting others.
Vaccination, testing and measures
Once people have been vaccinated, the vaccine will protect them from becoming ill from the virus. However, a person who has been vaccinated must still keep following the measures, just like everyone else. There are a number of reasons for this. The vaccines work well and are safe. However, there is a chance that you may become infected with the virus, even if you do not become seriously ill from it. By now, we know that vaccination also reduces transmission of the virus: people who are vaccinated are often less contagious. However, they could still be able to infect others. For the time being, it is therefore important for everyone to continue following the measures, and to get tested if they have symptoms.
Types of tests
There are various types of tests. Which types are there, and what do they tell us?
The PCR test
The PCR test detects specific fragments of genetic material from the coronavirus SARS-CoV-2. It is the most widely used and most reliable test. A smear is taken from the nose and throat with a cotton swab. This sample goes to a laboratory for the PCR test. The PCR test involves making copies of a small part of the virus. A small fragment of genetic material from the virus is replicated repeatedly, in order to detect its presence. The PCR test has a high test sensitivity. That means that the PCR test also detects the virus in someone who is not carrying much of the virus yet, or no longer has much virus left in their body.
What is the Ct value of the PCR test?
To ensure that the test will be as sensitive as possible, a specific fragment of the genetic material is amplified (copied) using the polymerase chain reaction method, known as PCR. This fragment of genetic material is specific to SARS-CoV-2. That means that the test cannot give a positive result for other viruses, such as a flu or cold virus. The genetic material is copied in ‘cycles’. During each cycle, the genetic material doubles in volume; this continues until it is detected by the PCR device. The Cycle threshold or Ct value is the number of amplification cycles required to detect the first signal that the virus is present.
COVID-19 testing for children
To control the spread of the virus, it is important to test as many symptomatic children as possible. A testing method designed specifically for children can help.
RIVMNational Institute for Public Health and the Environment investigated whether it would be possible to use a testing method adapted more specifically for children without making the test much less reliable. Reference literature and validation research by GGD West-Brabant and GGD Amsterdam among adults shows that this can be achieved by mid-turbinate nasal sampling (mid-turbinate refers to the middle of the nasal conchae, above the inner nostril). Using this method, the nasal swab is inserted less deeply into the nose: 1-2 centimetres depending on age, rather than 5-7 centimetres. Mid-turbinate nasal sampling is slightly less reliable than the current, deeper nasal sampling method. That is why the less deep specimen of nasal mucus is taken in conjunction with the current throat swab.
Since 4 April 2021, children aged 12 years and under who go to a GGD test lane are tested using this new method. In the GGD test lanes, younger children who are tested are given particular attention. Read more in the GGD GHOR news item about the updated testing method (in Dutch).
Video on testing children for COVID-19
The LAMP (loop-mediated isothermal amplification) test is a form of testing in which small fragments of genetic material are copied or replicated, similar to the PCR test. However, the method used for that purpose in the LAMP test is completely different from the PCR test. The major advantage of the LAMP test is that the fragments of genetic material are replicated at only one temperature. Therefore, this test is faster than the PCR test, which requires fluctuations in temperature. The LAMP test requires different equipment and chemical substances than are needed for PCR tests. As a result, they can complement each other in this respect, rather than competing if supplies become scarce.
The antigen test
The antigen test detects the presence of antigens for SARS-CoV-2 in nasal and/or throat mucus. Antigens are fragments of the virus (proteins) that can produce an immune response in the body. If you are carrying the virus, the antigen test will quickly show that result – usually about fifteen minutes after applying the sample to the test set. The test can also be used outside a laboratory setting. The antigen test is less sensitive than the PCR test Especially if virus levels are low, the antigen test will often give a negative result. At the very beginning of the infection, virus levels in the body are still low. Virus levels decrease again later in the infection, and the person will no longer be contagious by that point. If virus levels are low, a person may wrongly get a negative test result, even if they may still have COVID-19, or had it in the past.
Self-test (antigen test)
An antigen self-test is a COVID-19 test that you can buy in a shop, chemist or pharmacy to test yourself.
Self-tests are intended for people without symptoms, as a supplementary tool to identify infections that would otherwise go undetected. Self-tests are not suitable for:
- people with symptoms
- people who had contact with someone who has COVID-19
- people returning from a high-risk area
Self-tests are less reliable than a PCR test or antigen test done by a professional. Research shows that self-tests are between 58% and 78% reliable, as long as the self-test is used properly. That means there is a reasonable chance that someone may receive a negative test result on a self-test, even if the person is infected with SARS-CoV-2 and may be able to pass the virus to others.
A positive result from a self-test must always be confirmed with a professional PCR test or antigen test by the GGD.
This test is primarily used for research and screening at the population level, by selected laboratories. The serological test determines if there are specific antibodies against the coronavirus SARS-CoV-2 in your blood. Antibodies are part of your natural defences: the immune system. The body produces them in response to an infection with the virus. It can take 2 to 3 weeks for your body to produce the right antibodies and release them in sufficient quantities in your blood, so they can be detected. A serological test involves taking a blood sample. The test shows if you have had the virus in the past.
Breath test (breathalyser)
The PCR test and the antigen test are tests that have been used in medical laboratories for many years to detect the presence of other diseases. Tests for the coronavirus SARS-CoV-2 are also being developed that are based on less frequently used principles. One of those tests is the ‘breath test’ or breathalyser, also known as the electronic nose. Exhaled air is examined for molecules that indicate that you are infected with the virus. This test is mainly suitable for excluding the possibility that you are currently carrying the virus. A breath test can exclude the possibility of infection, but is not able to detect the presence of infection as precisely. A ‘positive’ breath test must therefore always be confirmed with a different test, such as a PCR, LAMP or antigen test.
On 6 September 2021, the Outbreak Management Team (OMT) stated in its advisory opinion that the breath test in its current form should no longer be used in the context of large-scale testing, such as in the GGD test lanes or in the context of testing for access. In field tests run at a number of GGD test sites, the breath test did not prove robust enough for widespread use.
When should each type of test be used?
As other types of testing become available, it is important to take a close look at how and when certain tests can be used in practice. Each test has its advantages and disadvantages, such as the speed of the result, the place where the test can be done (inside or outside a laboratory) and the sensitivity of the test. In certain situations, a false-negative result can have serious consequences. Examples include people who are seriously ill as well as vulnerable people in institutions. In such cases, it is important to use a test that is as accurate as possible. The PCR test is the best option for this purpose. The PCR is the ‘gold standard’, and the LAMP test is considered equivalent.
In situations where the disadvantage of a false-negative test result outweighs, for example, speed and flexibility, less accurate tests can also be used, such as the antigen test. The Outbreak Management Team advises the Cabinet about which individuals or groups can be tested with which type(s) of test. A clear table shows which test could be used in different situations.
Testing with and without symptoms
In general, the results of each test are more reliable when you have just developed symptoms. Since 1 December 2020, people who do not have symptoms can also get tested during their quarantine period from day 5 on.
The role for RIVM in testing
RIVM draws up the guidelines and protocols for testing and for source and contact tracing in cooperation with doctors, microbiologists and GGD GHOR. The Municipal Public Health Services (GGDs), laboratories and hospitals carry out the tests.
The quality of the tests being offered is very important in this context. Laboratories performing tests that can detect genetic material from the coronavirus SARS-CoV-2 must demonstrate in advance that they meet the quality requirements. RIVM supports them in that process.
Read more about the role of RIVM in testing
WHO Reference Laboratory
RIVM is a WHO reference laboratory and develops various diagnostic tests for the coronavirus SARS-CoV-2. These diagnostic tests are checked along with international partners. The techniques are then rolled out to laboratories in the Netherlands and abroad. The labs report the results of quality assessments to RIVM. RIVM looks at how a lab operates compared to other laboratories. Watch this video on the reference laboratory.
Testing capacity in the Netherlands
The Dutch Government, together with the Municipal Health Services (GGDs) and the National Coordination Team Diagnostic Chain (LCDK), ensures that there are enough test sites, test materials and laboratories that can test for the coronavirus SARS-CoV-2.