It is likely that most people during the pandemic have experienced or will experience symptoms of an infection, wondering if it is sometimes COVID-19. Some particularly characteristic symptoms, such as loss of smell and taste, most likely indicate infection with SARS-CoV-2 virus. However, for many infected, the course of the disease may resemble the flu or a cold – then quick cassette tests intended for home diagnosis are helpful in the diagnosis of COVID-19.
Today, both antigen and serological tests are widely available, and anyone who suspects they have COVID-19 can do the test themselves at home. How are the two tests different and which one to choose?
COVID-19 symptoms
The spectrum of COVID-19 symptoms is very wide – from asymptomatic cases to severe respiratory failure. The most common symptoms of infection include high or low body temperature, runny nose, cough, headache, muscle aches, sore throat, fatigue, as well as diarrhea, conjunctivitis or rash. Especially characteristic of COVID-19 are changes in the sense of smell and taste, which are sometimes the only sign of the disease.
Less common symptoms are more often seen in the elderly or immunodeficient – decreased appetite, confusion, sleepiness, nausea, or vomiting.
In nearly 80% of patients, the course of SARS-CoV-2 infection is mild – slight symptoms disappearing within 1-2 weeks.
Antigen tests
The method of operation of antigen tests is based on the detection of antigens specific for a given virus. To understand how such a test works, we first need to know what antigens actually are. Simply put, antigens are characteristic fragments of the microbial structure, e.g. proteins, glycoproteins or lipids. Their presence in the tested biological material proves infection.
The test is based on the use of specific antibodies against SARS-CoV-2 antigens contained in the test cassette. These antigens include the viral nucleocapsid proteins and the SARS-CoV-2 (S protein) fusion protein. Virus S fusion protein Spike) by binding to cellular receptors (receptors for angiotensin-converting enzyme II protein found mainly in the lungs), it allows the virus to enter the host cell and replicate.
What is the procedure for performing such a test? The first step is to collect the material for the test, i.e. make a smear – usually from the nose or nasopharynx. Remember that the correct collection of the preparation is a condition for obtaining a reliable test result. In the next step, place the collected material on the window of the test cassette and read the result after 15 minutes.
You can buy the home COVID-19 Ag SGTi-flex cartridge test at medonetmarket.pl. We also recommend the COVID-19 Check up quick antigen test, the result of which can be read just 15 minutes after taking it.
Serological tests
The serological test detects SARS-CoV-2 infection indirectly, i.e. by detecting antibodies (in the IgG and IgM class). Antibodies are particles that circulate in our blood to detect and neutralize microorganisms, e.g. viruses, bacteria. They are produced by the cells of the immune system, and more precisely by the so-called plasma cells.
The body produces various types of antibodies, among which we distinguish, among others IgM and IgG antibodies. IgM antibodies are produced from the very beginning of symptomatic infection and are the main line of defense until the body produces IgG antibodies. IgG antibodies are produced with a delay and may be present in the blood for many years after infection (or vaccination).
In the Rapid Serological Testing, the test material is blood taken from the fingertip. As in antigen tests, the sample is placed on the window of the test cassette and the result is read after an appropriate time.
Which test to choose?
When we observe symptoms of COVID-19, we expect quick and reliable diagnostics. Cassette tests – both antigenic and serological – can be performed as part of self-control without leaving your home. But which test is better for a newly diagnosed infection?
The antigen test is generally more accurate than the serological test. This is because it directly detects the virus antigen (protein S or protein N). The serological test, on the other hand, only detects the response of our immune system to infection (IgG / IgM antibodies), not the virus itself. Moreover, at the onset of the disease, the antibody titer may be too low or absent altogether.
Taking into account the above-mentioned properties of both tests, an antigen test will be a much better choice for the diagnosis of the current infection. Rather, the serological test will be used to confirm or rule out a history of COVID-19.
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