ANTIBODIES & ANTIBODY TESTING IN COVID-19
Antibody response to infections :
Antibodies are proteins produced by the human body in response to an infection and help fight it off. They can stay in the blood for months to years and help in countering future attacks by the same infection. These antibodies can be produced after vaccination. Vaccination works by evoking these protective antibodies in the body, but without actually giving us an infection.
Detecting and measuring antibodies is important because it can tell you:
• Whether you have any degree of protection against future infections:
Presence of specific antibodies is indicative of protection against future infection by the same strain of virus.
• Whether you have had an infection:
It is common knowledge now that COVID-19 can be completely asymptomatic. So, you may have had an infection without even knowing it.
• Whether the vaccination has worked:
In some cases, especially in people with compromised immune systems, antibody response even post vaccination may not be adequate for protection.
There are 2 main types of antibodies IgM and IgG. As a thumb rule, in most infections, IgM arrives on the scene first (usually within a week to 10 days) and at least a week later, IgG appears. However, this pattern varies from disease to disease. IgM then slowly peters out while IgG persists for years and can provide future immunity against the causative microorganism.
So, usually detection of IgM indicates that the infection is still in its acute phase and detection of IgG indicates the infection has passed.
RT-PCR has been the mainstay in the diagnosis of the disease from the beginning. This is a direct diagnostic test and a positive result is confirmatory of the presence of COVID-19 infection. A positive antibody test, on the other hand, is only a surrogate marker of a recent infection. Therefore, ANTIBODY TEST, BY ITSELF CANNOT BE USED FOR DIAGNOSIS OF AN ACTIVE INFECTION.
When used judiciously and in combination, the results of RT-PCR and antibody tests can be of great help in stratification of the population vis-à-vis actively infected population, recently infected but recovered population, and the normal population.
An algorithm based on these considerations is given below as a general guide for the population at large (source: CDC, Atlanta, USA). . All are encouraged to follow these guidelines and help the healthcare and regulatory authorities in controlling and, if possible, in eradicating the pandemic.
|Viral testing (Testing for current infection – PCR/Antigen)||Positive||Most likely have an active infection|
|Negative||Most likely do not have an active infection|
|Antibody testing (Testing for evidence of past infection)||Positive||Likely had a COVID-19 infection in the past, OR had a successful antibody response after vaccination|
|Negative||Likely never had a COVID-19 infection or never developed antibodies to a past COVID-19 infection|
|Both||Viral Positive, Antibody Positive||Most likely have an active infection|
|Viral Positive, Antibody Negative||Most likely have an active infection|
|Viral Negative, Antibody Positive||Likely had and recovered from a COVID-19 infection, OR had a successful antibody response after vaccination|
|Viral Negative, Antibody Negative||Likely never had a COVID-19 infection|
Suburban Diagnostics offers the full range of COVID-19 antibody testing.
For the ease of understanding, our antibody tests can be broadly classified into two types:
1. For testing during or after infection
These tests are for detecting antibodies after being diagnosed with COVID-19 infection. As mentioned above, it can tell you whether you have developed antibodies against COVID-19 while giving you protection against future infection.
|Anti SARS-CoV-2 Antibody, Total, Serum||Most sensitive and earliest marker of immune response after and infection|
2. For testing after vaccination
Vaccinations give you protection against COVID-19 by inducing certain specific antibodies. Testing for antibodies post your vaccination can let you know if the vaccination has worked on your immune system. If you have developed the antibodies, a quantitative test can tell you how well your body has responded by measuring the level of antibodies in the blood. This can then be tracked for the future – to assess if the levels have gone up or down.
|Anti SARS-CoV-2 Antibody, Post-Vaccination, Quantitative, Serum||Test designed to determine development of antibodies and know how much antibodies have developed post vaccination.|
Quick reference of Antibody tests at Suburban
|Test Code||Name of Test||Turnaround time||MRP(₹)|
|PATH001489||Antibody Check (SARS-CoV-2-CLIA)||3 hrs. post the same is received at the lab (Cut-off: 7:00 PM)||Rs 450/-|
|PATH001507||Post Vax Antibody Check||3 hrs. post the sample is received at the lab* (Cut-off: 3:00 PM)||Rs 1,500/-|
What is an antibody?
• An antibody is protein that develops in the body as a normal part of the immune response to many types of infections.
• Our bodies develop antibodies in days and weeks after being infected or after vaccination against COVID-19.
Why should a person get a COVID-19 antibody test performed?
Detecting and measuring antibodies can tell you:
• Whether you have any degree of protection against future infections: Presence of specific antibodies is indicative of protection against future infection by the same strain of virus.
• Whether you have had an infection: It is common knowledge now that COVID-19 can be completely asymptomatic. So, you may have had an infection without even knowing it.
• Whether the vaccination has worked: In some cases, especially in people with compromised immune systems, antibody response even post vaccination may not be adequate for protection.
What does the COVID-19 antibody test do?
• As mentioned, antibodies are proteins that your body makes to fight an infection. The presence of antibodies indicate that the immune system has seen the virus and begun a reaction against it. These antibodies develop in most patients within one to three weeks after symptoms of COVID-19 begin and remain in the blood after the infection has passed.
• Antibodies are also developed after being vaccinated against COVID-19.
• COVID-19 antibody tests detects the presence of these antibodies.
Can these tests be used to diagnose COVID-19 infection?
• NO. This test is not intended to be a diagnostic test. It is intended to identify if a person has contracted COVID-19 in the past, OR to determine if they have developed protective antibodies after vaccination.
Does this test correlate with the severity of the disease?
• No. In fact, the result may indicate you were infected with the SARS-CoV2 virus even if you showed no symptoms whatsoever. A person who was hospitalized in critical condition and a person who had barely a slight cough could both show antibodies to this virus. It had nothing to do with the severity of the disease.
How are antibody tests performed?
• Antibody tests are blood tests that are conducted through a simple blood draw. The blood is then sent to the lab to be inspected for the antibodies.
How long does it take to receive test results?
• If a sample is collected in Mumbai, results can be expected within 24 hours.
If I presently don’t have COVID-19 symptoms, should I get the test?
• You can get yourself tested even if you are asymptomatic, because the test will tell you if have had the infection in the past.
If I have a positive COVID-19 antibody test, am I protected against future infections?
• A positive antibody test means that you have developed an immune response to the COVID-19 virus and that you have some degree of protection against future infection
When can this test be done?
• This test is best performed atleast 2 weeks after the onset of symptoms or 2-3 weeks after completing the vaccination schedule. The timing and type of antibody test affects accuracy. If you testing too early when the immune response is still building up in your body, the test may not detect antibodies.
Is social distancing needed if I have antibodies?
• Yes, it is important to continue social distancing, frequent hand washing, respiratory etiquette, and practice proper hygiene since it’s not certain that having antibodies means that you’re immune to subsequent infection from the COVID-19 virus.
• Furthermore, people can transmit viral particles on their hands, face, other areas of the body, and clothes, even if not infected. This can then increase the risk of infection to others.
Should I be concerned for my health on taking the COVID-19 antibody test?
• There are currently no known medical risks related to taking the COVID-19 antibody test, beyond that typical of a blood draw.
• If you or your family member taking the antibody test has had issues or concerns with blood draws in the past (bruising, bleeding, fainting, etc.), please alert our centre staff or our phlebotomist and they will advise the best course of action.
Are there special tests for antibodies if I want to check whether my vaccination has been successful?
• Yes, we have a test which can measure the level of specific antibodies that are produced once you have taken the vaccination.
How much does the COVID-19 antibody test cost?
• The COVID-19 antibody test costs INR 450 if blood collection is done at our lab. Additional charges will be applicable for a home visit, depending upon the patient's location from the nearest lab.