Terms like antigen, antibody test, Covid-19 test, plasma, RTPCR, rapid test kit, ventilator, lockdown, social distance, etc., have become part of our daily word choice in this Covid-19 pandemic. While these words have become a part of daily life, people tend to get confused between the antibody test and the Covid test. Usually, the antibody test is done to check if the body has developed antibodies against certain diseases. Let's discuss some basic facts about the Corona Virus antibody test.
Basics of antibody
The human body produces antibodies to fight off the infection when it senses the presence of an external invader, such as a bacterium or virus. Antibodies are basically Y-shaped proteins and white blood cells produce them. This protein helps to fight against harmful germs and get cured.
IgM and IgG antibodies are produced in the body of an infected person who has normal functioning of the immune system, which can be detected by serologic tests or antibody tests. IgMs are usually formed within one to two weeks of infection, but these are lost very quickly. IgG antibodies, on the other hand, take about 6 weeks to form, but they last longer.
According to the US Centers for Disease Control and Prevention (CDC), some Covid-19 patients may detect antibodies in the first week of infection. In other Covid-19 patients, it may take up to three weeks for antibodies to be produced against the coronavirus.
That is why the patient should wait up to three weeks after the symptoms to test for the Covid-19 antibody. Further, the CDC report states that testing for antibodies three weeks after coronavirus infection can detect both IgM and IgG antibodies.
What is the antibody taste for Covid-19?
Covid-19 antibody test, which is also known as serology test, is a way to measure if someone had been infected with coronavirus in the past. However, the antibody test cannot identify if someone is currently infected or not. To check the present condition, one should do the antigen test diagnostic test for Covid-19.
However, a positive antibody test will not ensure that the person will not get infected again. If someone has an antibody in the body, it is very difficult to say how long the antibodies against coronavirus will last. According to the CDC's website, it is still rare for Covid-19 to be infected twice, but people are also getting infected twice or more than that. However, the CDC suggests that coronavirus antibodies may provide immunity, at least in the short term. So, after a certain period, the antibody test may not show a positive result.
A recent study published in the journal Nature Medicine suggests that coronavirus antibodies may not provide protection in the long run. The researchers found that antibody levels decreased within two to three months of curing Covid-19, especially in asymptomatic Covid-19 patients. However, it was a small study, analyzing only 36 symptomatic cases and the same number of asymptomatic cases. So, an antibody test after two to three months may not locate the antibody in the body.
What is the purpose of Covid-19 antibody testing?
Antibody testing lets the researchers and doctors know how the body reacts to the virus as well as collect the symptoms. Furthermore, it also gives data on the frequency of the infection. However, the antibody test should not be done to decide if anyone can take the vaccine or not.
Who is eligible for the Corona Virus antibody test?
If someone is infected with Covid, the antibody may take time to build in the body. So, testing on the most recent patient will not be wise. If someone is just diagnosed with corona or treated in two to three weeks, it will give positive results on an antibody test. So, it is suggested that antibody tests can be done four to six after being cured.
How to do the Covid-19 antibody test?
This test is very easy to do by taking a few drops of blood from the tip of the finger. Moreover, it does not take much time; the test can be done in 15 minutes. Nevertheless, this test is to be used in different countries to find people who are free of infection, and those people can be out of the house. Antibody tests will be very effective, especially for health workers. But making the test kit is not so easy. The US FDA approved antibody tests last year.
Types of antibody test
So far, two types of antibody tests are available, binding and neutralizing antibody tests. The binding test uses the purified proteins of SARS-CoV-2. In this method, individual antibody types, like IgG, IgM, and IgA can be identified. Hence, SARS-CoV-2 IgM and IgG antibodies can be found at the same time through the binding antibody detection system.
On the other hand, the neutralizing antibody detection tests find the functional ability of antibodies. These kinds of the test monitor the inhibition of viral growth in the cell when raised with plasma or serum. The neutralizing antibody is categorized into three types, virus neutralization tests (VNT), Pseudovirus neutralization tests (pVNT), and Competitive neutralization tests.
Antibody test result
Usually, the Covid-19 test result is explained in four ways. If there is a positive IgM, then the patient may be considered infected at the moment; if there is only IgG, then it may be that he is recovering from the infection, and it is possible that he will not be infected in the future. If both are positive, it can be assumed that the patient is at the end of the infection. And if none shows up, the patient is not infected. Sadly, this last statement is not always correct. It may be that the antigen used in this test does not recognize the patient's antibodies. Again, the patient may have been infected, but not enough time to make antibodies.
Is the coronavirus antibody test easy?
The health care workers have a mixed response to this question. Even if the kit works, there is a possibility of false-positive and false-negative results in the COVID-19 antibody test. If a small number of people in the population (say 4.5%) are infected, there is a 50% chance that they will actually be positive. On the other hand, if 30% of the people are infected, and positive results are obtained, in 90% of the cases, it will be true. It was also thought that people who had been infected would have enough antibodies in their blood to fight the virus if they were given to an infected patient.