COVID-19 has expanded into a pandemic since January 2020, being able to infect humans at a lightning fast rate.
Many diagnostic tools used to detect the presence of Coronavirus infection, while some identify virus and some identify antibodies
produced to fight the virus. Out of which, the most promising and preferred
method is Antibody Testing or also commonly known as Serology Test. The
antibodies are produced in human body after they have encountered an antigen
that might be bacterial or viral pathogen. This helps the human body to generate
immunity.
Antibodies and its target:
There are 3 antibodies that may be checked for
positive infection:
|
|
IgM Immunoglobulin M |
IgG Immunoglobulin G |
IgA Immunoglobulin A |
|
Produced in Human body |
First one to be produced. |
Produced later within 14 days of infection |
Already Produced and present. |
|
Immune Response |
Primary |
Secondary |
Primary |
|
Size |
Largest antibody |
Smallest |
- |
|
Presence |
Blood |
Serum (primarily) |
Serum, Mucosal secretions, sweat glands, saliva,
tears, Blood. |
|
Structure |
Monomeric at the surface of B lymphocyte and Pentameric if freely
floating in the Blood. |
Monomeric |
Dimeric |
|
Specificity |
Not highly Specific |
Highly Specific |
Not specific |
|
Role |
Binding to majority of the antigens and rapid
clearance of the antigens from the Blood stream. |
Direct neutralization of the antigen. And causing
Antigen clearance via the cell mediated process. Responsible for
Post-infection Immunity. |
Protect mucosal surfaces. |
|
Concentration present in blood |
10% of total antibody count. |
Most abundant: 80% of total antibody count. |
10% - 15% of total antibody count. |
Time for the Test:
The complete test takes around 2-3 days to give the
results.
Benefits:
The primitive benefit of having antibody testing is that the results also disclose some other details like:Method of Testing:
These tests are done by taking out some blood and
carrying out tests to find the target antibodies by using Immunological
methods, like ELISA, Lateral flow assay Chemiluminescent Immunoassay.
Approval of the tests in India:
Antibody testing is used widely in India & is approved
by the FDA, NIH, CDC, and NCI.
Limitations:
The antibody tests are not regarded as completely
reliable as there can be errors in the binding of the antibodies while
testing. The new error that’s generally found is the neutralizing antibodies.
These antibodies of IgG type are responsible for preventing the entry of
the pathogen. Presence of this antibodies do not mean that the person has a
thriving COVID infection. It takes around 3 days to get the results, while the
antigen testing requires 2 days.
Thus, this is an effective test with its pro’s and con’s. The government uses this test in addition to the other testing procedures for better results.
Inputs by Vaibhavi Mullassery
