The Pune-based National Institute of Virology (NIV) has developed an immunological assay — enzyme-linked immunosorbent assay (ELISA) — to detect antibodies that the body develops in response to infection by the SARS-CoV-2 novel coronavirus.Antibody tests are critical for surveillance to understand the proportion of population exposed to infection

• The test will detect IgG antibodies present in blood samples.
• This kit was validated at two sites in Mumbai and has high sensitivity and accuracy.
• It has the advantage of testing 90 samples together in a single run of 2.5 hours.The test is named as “COVID KAVACH ELISA”
• The ELISA test developed by NIV gains significance as the rapid antibody tests imported from China were found to be unreliable and hence States were instructed not to use them for detecting previous coronavirus infection.
• The ELISA test will be used to screen 30,000 samples from 75 hotspot districts to understand the extent of spread of the virus in the community.
• ICMR has partnered with Zydus Cadila for mass scale production of the ELISA test kits.

 

Antibody Test Vs RT-PCR Test:

While real time RT-PCR is the frontline test for clinical diagnosis of SARS-CoV-2, robust antibody tests are critical for surveillance to understand the proportion of population exposed to infection.

Types of Tests To detect COVID-19

ELISA test is based on detection of antibodies, it can only help in knowing if the person has been previously infected by coronavirus. Since it detects antibodies, even people who have remained symptom-free (asymptomatic) during the entire course of the infection will test positive.

While the RT-PCR, which detects the RNA of the coronavirus, enables detection of current infection, it will not be useful if the testing is carried out days after the infection clears as the virus will no longer be present. However, antibodies developed in response to the coronavirus infection will be present in the blood for a longer duration and hence the ELISA test can help detect past infection. The maximum time the antibodies will be present in the body is not known for coronavirus.

What is ELISA?

An enzyme-linked immunosorbent assay, also called ELISA or EIA, is a test used to detect and measure antibodies in your blood.

It is commonly used to measure antibodies, antigens, proteins and glycoproteins in samples. Some examples include: diagnosis of HIV infection, pregnancy tests, and measurement of cytokines or soluble receptors in cell supernatant or serum.

The ELISA test involves taking a sample of your blood.

Procedure:

The blood sample is sent to a laboratory for analysis. In the lab, a technician  adds the sample to a petri dish that contains the specific antigen related to the condition for which you are being tested. Given that your blood contains antibodies to the antigen, the two will bind together. The technician will check this by adding an enzyme to the petri dish and observing how your blood and the antigen react.You may have the condition if the contents of the dish change color