An antibody test for COVID 19 will tell you if you have have developed immunity to the Corona virus after coming in contact with it. Presence of antibodies indicate some immunity and lack of them indicate susceptibility. They are used to survey a population for prevalence.
Welcome. I had asked a question before as to what you would do if you had been close to a person with a corona virus infection and suppose the RT- PCR tested had come out as negative.
I had mentioned that an antibody test would give a record of whether you had encountered the virus and formed defense mechanism against it. The result if this antibody test will provide guidance about your resistance or susceptibility. It will inform you if you have already contacted the virus and developed immunity without your knowledge or whether you are still susceptible or at risk in spite of the contact you made with an infected person.
So, in this video I am going to explain about the antibody test.
At this point I wish to ask you if you have had an antibody test. Chances are that if you went in for a surgical procedure, you might have had several tests for hepatitis and HIV.
The purpose of the antibody test is to try to determine if your immune system has reacted to the virus. Under normal circumstances if the person is not immuno-compromised the immune system will react to foreign substance or an antigen in the form of a virus bacteria or protozoa by forming neutralizing antibodies and long-term memory retaining cells. Antibodies are proteins that your immune system creates
Let’s first see how antibody tests work.
Antibody test look for antibody against SARS- COV 2 usually in your blood. So, you might ask what antibodies are. Antibodies are proteins that your immune system creates when you have been exposed to a virus. These antibodies help you to fight off that virus if you encounter it again. The antibodies that most SARS -COV 2 antibody tests are trying to detect are immunoglobulin M and immunoglobulin G. In short IgM and IgG.
IgM is the first type of antibody your immune system makes when you are fighting a new infection. IgG comes later when you have cleared or almost clear an infection and it stays for longer. So, I GM appears first and disappears quickly. IgG comes later and stays for longer.
The test available in India at the moment for serological surveillance is called the Kavach ELISA test.
In this test 2 CC of venous blood is taken and is placed on the test strip. The test kit has got the antigens of corona virus embedded in gold nano particles. Your blood starts to move down the strip where it comes across SARS COV-2 antigens embedded in the test strip. To recapitulate, antigens are parts of the virus that your immune system might recognize like a piece of the spike protein.
This test kit only detects whether you have igG antibodies but others may detect IgM and IgG antibodies.
If you have IGM and IgG antibodies in your blood that are specific to SARS COV 2 antigens, they will bind to those antigens which are present on the test strip. There are three potential lines on this strip, namely M, G and C. The first and second M and G correspond to the antibodies IGM and IgG. The third line C will inform you if your blood sample made it all the way down the test. Now let’s see what the results might turn out to be. Let’s say that this test is 100% accurate. You might see a combination of things.
A line at M would mean that you have been infected with COVID 19 recently and are still fighting off SARS-COV -2. You have the first early type of antibodies known as IgM antibodies now. You are infectious as of now.
A line at G and C means that you are at the end of the fight or maybe a while ago. It means that you have got IgG antibodies which came later and are still present in your blood. It means that you are at least partially immune to the virus for now. Further data on the duration of immunity is awaited.
A line at M, G and C would mean that you are somewhere in between.
Just a line at C would mean that you don’t have any antibodies to SARS-COV 2 and so you probably weren’t exposed to it.
All this seems to be very straight forward. Antibody test or not new and I’ve been around for a while. Any prospective surgical patient must undergo an antibody test for HIV which is called a rapid ELISA test.
The role of antibody test is for serological surveillance. It means to survey how many people in a population have had an exposure to the virus. Epidemiologists use this test to get an idea of the prevalence of the infection in a population and use this to calculate the infection fatality rate.
Several more antibodies are in the pipeline to enter the Indian market.
There are issues with these antibody tests and that will be the topic of my next video. So, stay tuned and share it with your friends. Kindly subscribe if you haven’t done so till now. I’ll see you soon.
