De PCR (polymerase chain reaction)-test detects the presence of small fragments of genetic material from the coronavirus SARS-CoV-2 in nasal mucus. It is the most widely used and most reliable test for the virus.
With a PCR test, a smear is taken from mucus in the nose with a cotton swab. If the virus is present in the mucus, this test will make copies of part of the virus. A small fragment of genetic material from the virus is replicated repeatedly, in order to detect its presence. This is also referred to as an amplification test. The PCR test is very sensitive. That means that the PCR test also detects the virus in someone who is not carrying much of the virus , or no longer has much virus left in their body.
The PCR test is used in the GGD test lanes or at other test sites. The test is also performed in hospitals.
The antigen test detects the presence of antigens for SARS-CoV-2 in nasal and/or throat mucus. If you are carrying the virus, the antigen test will quickly show that result. The antigen test gives a quicker result than PCR, but is less sensitive.
The Antigen test shows the presence of SARS-CoV-2 (Covid-19) in nasal/throat mucus. Antigens are pieces 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. he 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, but it is still possible for the person to test positive after that. Virus levels decrease again later in the infection, and the person will no longer be contagious by that point.
Source: Dutch National Health Services – https://www.rivm.nl/en/novel-coronavirus-covid-19/testing