RT-PCR is widely used to detect COVID-19. It is a universally accepted diagnostic test for SARS-CoV-2 virus.

The antibody test is a method to detect antibodies in your body against the COVID-19 infection. This test is not diagnostic. It is useful to identify the level of infection in people.

The antibody test is completely different from the usual swab test. Antibodies are proteins produced by the immune system against infection. They are specific to that particular infection.

To test antibodies, patient’s blood sample is collected. One or both kinds of antibodies to SARS-CoV-2 virus will be checked.

IgM antibodies reveal the early stage in an infection and IgG antibodies reveal the later stage.

Usually, IgG antibodies appear 14 days after the onset of symptoms. Indication of IgG antibodies in the blood reveals that the person is infected with SARS-CoV-2 virus in the past.

The infection may have happened from weeks to months in the past. But, this test does not reveal whether the infection had gone or you could still be contagious.

If IgG is present in the body, it gives immunity and protection against the diseases in case of some infectious diseases. However, there is not much known about COVID-19.  Hence, it is not known completely whether IgG gives immunity against COVID-19 or, if it does, how long would the immunity last.

The negative test result normally means that you have not been infected with SARS-CoV-2 virus in the past. However, in some people, the test is a false negative. Besides, IgM antibodies from other health conditions like common cold are also mistaken as SARS-CoV-2 antibodies.

Several researchers also said that these tests are not peer-reviewed and found to have a high rate of bias.  Hence, the antibody test is not completely accurate.

Photo by Bicanski on Pixnio public domain (CC0)

Image Reference: https://pixnio.com/media/antibacterial-antibody-antigen-antitoxin-coronavirus