COVID-19: How COVID Test Works?
What test methods do doctors use for COVID-19 (SARS-CoV-2) detection and diagnosis?
Coronavirus tests use two SARS-CoV-2 detection approaches, causing the disease of COVID-19 and weakening and potentially fatal viral pneumonia.
The tests are as follows:
- Genome-based detection (molecular)
- Detection-based immunoglobulin (serology)
How do COVID-19 gene tests work?
The first and most common method for detecting the virus in individuals is by detecting SARS-CoV-2 specific genetic material in the nasopharyngeal secretions of a person.
Even though test kits vary greatly in their procedures (swabs of oral and/or nasal surfaces, differences in tissue transfer solutions, time and place, etc), all of them employ techniques to detect a particular portion of the viral genome.
An example of how a COVID-19 test system does this is given here:
- The swab tissue is placed into a regular vial for reaction
- Reagents (the general term for supplementary chemicals required for testing) break open viruses to expose viral genomes (RNAs), which are related to a certain small area of the viral RNA, to other reagents such as synthesized RNA
- In several tests, up to a billion times, this small binding range of virus genomes and reagents is then replicated over minutes to hours!
- Then another reagent binds in particular to each genetic complex replicated at the same time.
- This reactive has a limitation marker that the machines can detect the attached marker if sufficient replicated complexes are made.
- The marker may, for example, be designed to fluorescence, which can be taken by the machine on its sensors.
- In minutes or days, the findings may be positive (depending on the test used) depending on how many viruses are found in the sample.
- Conversely, if the test detects no viral material after a fixed time (minutes to days), the result is a negative test
What is the significance of the COVID-19 test?
The qualitative findings are that either a person has SARS-CoV-2 infections and is able to pass (a positive test) the disease or is adversely affecting the virus.
This test does not know if a person has or still needs to be subjected to a past infection and is, however, still at risk.
What are COVID-19 coronavirus immunoglobulin-based tests?
The immunoglobulin research is focused on qualitative identification of IgM, IgG, and SARS-CoV-2 directly developed by the body.
IgM produced by the body in response to infection is typically the first, particular form of the antibody. In response to infection, the IgG type anticörper is created and substitute IgM as the prevailing antibody.
IgM and IgG are fighting infection by attacking unique SARS-nCoV-2 antigens on the skin.
Immunoglobulin experiments are typically using particular viral antigens to detect IgM and/or IgG antibodies.
Here is a sample of how the test works:
- Collect 2-3 drops of fresh blood/serum or plasma and place it in a sample container and place 2-3 drops of provided buffer in the same container (cassette)
- The cassette allows the diluted sample to move through the cassette by capillary action
- The cassette has labeled SARS-CoV-2 antigen that may bind chemically with either IgM or IgG; thus, forming an antigen/antibody complexes of antigen/IgG and/or antigen/IgM
- After that reaction, the antigen/antibody product passes over anti-IgM and anti-IgG antibodies that are immobilized in a line within the cassette
- The anti-IgM and/or anti-IgG then will capture the specific complex and signal a result (a red line) if either complex is bound to the immobile anti-IgM or anti-IgG
- The results need to be read after 10 minutes and no more than 15 minutes (the test resembles a home pregnancy test in this respect.)
- A third line is a control line; it indicates that the test is working properly
What do the COVID-19 immunoglobulin test results mean?
A total of three detection lines are possible, the control with (C) line appearing when sample has finished flowing through the cassette, indicating the test is complete.
The following are what the results mean:
- Negative Result: If only the quality control line (C) appears and the detection lines G and M are not visible, then no novel coronavirus antibody has been detected and the result is negative.
- Positive Result, IgM only: If both the quality control line (C) and the detection line M appear, then the novel coronavirus IgM antibody has been detected and the result is positive for the IgM antibody.
- Positive Result, IgG only: If both the quality control line (C) and the detection line G appears, then the novel coronavirus IgG antibody has been detected and the result is positive for the IgG antibody.
- Positive Result, IgG and IgM: If the quality control line (C) and both detection lines G and M appear, then the novel coronavirus IgG and IgM antibodies have been detected and the result is positive for both the IgG and IgM antibodies.
Immunoglobulin tests for COVID-19 cannot confirm the presence of the virus in your system. It can only tell whether you have been exposed in the past or if you have never been exposed to SARS-CoV-2. Consequently, it should only be used alone as a screening test and should be used in tandem with a genetic-based test to determine a complete status. Genetic testing is the gold standard for COVID-19 diagnosis.