Because the symptoms of COVID-19 that most commonly occur (fever, cough, difficulty breathing) are similar to other illnesses (respiratory illnesses, flu, allergies), laboratory tests are needed to determine whether COVID-19 infection is present or absent. It is also possible through testing to identify asymptomatic people who have the infection and can spread it.
Access to testing is important, but the results it can give are even more important. Tests are not all the same and each type of test comes with advantages and disadvantages. It’s best to search for covid testing near me to find a qualified clinic that can perform a proper test on you.
Rapid tests based on antigen detection identify the presence of coronavirus proteins (viral antigens) in nasopharyngeal secretion samples collected from patients. Viral antigens are proteins in the virus structure that determine the body's specific immune response to the virus. Nasopharyngeal secretions from the patient are placed on a paper strip on which antibodies specific to the SARS-CoV-2 coronavirus are fixed. If the secretions contain viral antigen there will be a visible reaction between the antibodies on the paper strip and the viral antigens in the secretions.
Advantages of the rapid antigen test
RT-PCR is the gold standard when it comes to diagnosing COVID-19, but the rapid antigen test has two clear advantages:
The antigen test is faster
One of the benefits of rapid antigen testing is the greater speed of testing compared to RT-PCR, which gives a result in about 48 hours.
Antigen testing is cheaper
Rapid viral antigen testing is also less expensive than RT-PCR testing.
Disadvantages of the rapid antigen test
Although the rapid antigen test is a good alternative to the standard test, it also has disadvantages: the accuracy is not the same as for the RT-PCR test because it depends on the amount of virus, but also on the number of days that have passed since the onset of the disease.
For example, if the result is positive, indicating the presence of viral antigens, it does not mean that there may not be a bacterial infection or co-infection with other viruses in the body.
Negative results also do not rule out infection with SARS-CoV-2. In this situation, further analysis of the patient's health status and even confirmation with an RT-PCR test, where appropriate, should be done.
When is rapid antigen testing indicated?
Rapid antigen testing has a number of recommendations. Thus, rapid antigen testing is indicated when:
- the person already has symptoms of COVID-19; it is important that the test is done as soon as possible, ideally within the first five days, when the viral load is highest;
- the person is asymptomatic, but is in direct contact with a confirmed positive person; the test should be done no later than seven days after contact;
- there is already an outbreak of COVID-19; rapid testing can help early detection and thus isolation of cases;
- there is a need for screening in high-risk areas and confined spaces, such as hospitals, schools, nursing homes and psychiatric centres with chronically ill patients; if we are talking about repeated screening, this should be done every 2-4 days, and if the result is positive, then it should also be confirmed by RT-PCR;
- population-wide screening is needed to stop the spread of the virus as much as possible.