There are three kinds of tests:
1- Molecular test (RT-PCR): detects the genetic material (RNA) of the virus in a sample collected from the respiratory tract using a swab.
2- Serology test: detects antibodies produced in response to the infection in blood samples.
3- Antigen test: detects a viral protein in respiratory samples.
In general, serological tests are blood-based tests that are used to determine whether people have been infected by particular pathogens. The immune system recognizes pathogens as foreign and mounts a protective response involving the development of antibodies. The presence or absence of SARS-CoV-2 specific antibodies can determine whether or not a person has been infected by the virus.
IgM and IgA are the first antibodies to appear after recent infection, followed by IgG antibodies, which are more specific and last longer than the other antibodies. IgG antibodies can be detected starting from 10 days after exposure to the virus. However, some people do not generate detectable IgG antibodies after infection, because of many reasons, for example; an existing auto-immune disorder. Also, the immune response may be different from one individual to another based on the viral burden and other factors.
Life Diagnostics uses fully automated laboratory-based immunoassays from manufacturers who have demonstrated thorough validations of their kits. We also verify the performance characteristics of the kits by performing precision, accuracy, and other necessary validation studies.
Serological tests (Antibodies detection) are not used to diagnose recent infection with the virus. Instead, they provide information on whether or not a person was previously exposed to the virus and has developed antibodies against it. The test that is used to diagnose recent infection is the molecular PCR test.
This means that the IgG antibodies are not detected. IgG antibodies start to appear at a detectable level in the blood after at least 10 days from the onset of the symptoms. This can vary from an individual to another. However, it is important to mention that Negative results do not rule out COVID-19 infection, especially in people who have been in close contact with patients affected by the virus. In these cases, a molecular diagnostic test (PCR) is advised.
Borderlines results mean that the IgG is detected at a level that is too close to the detection limit level of the assay. This may mean that there may be an early infection, or a cross-reaction with a similar virus, or an underlying immune disorder.
A positive result may indicate that you are immune to the virus and may not get the infection again. However, SARS-CoV-2 is a new virus and there are still unanswered questions about whether a previous infection provides immunity and if so, for how long. Research is underway to clearly understand the protective effects of SARS-CoV-2 antibodies and the time span of the immunity that they provide.
- People who have experienced no symptoms and wish to see whether or not they have developed antibodies to the virus.
- After 10 days of being exposed to the virus, or after symptoms resolve.
- To identify people who have recovered from the infection, and who may be able to donate blood to patients for treatment.
Life Diagnostics offers a high-complexity qualitative immunoglobulin G (IgG) immunoassay for SARS-CoV-2; the virus that causes the disease known as COVID-19. This is a laboratory-based fully automated test and not a rapid test.