ELISA-based Antibody Test
On Monday, a day after the Center announced that an ELISA IgG test for the detection of antibodies against Covid-19 had been developed, it published a document detailing the details of the surveillance that will be carried out in all districts to verify the prevalence of infection using the same.
The Pune-based National Institute of Virology has developed an immunological assay, enzyme-linked immunosorbent assay (ELISA), that can detect antibodies that develop in response to coronavirus infection. Health Minister Dr Harshvardhan said this is the first such test to be developed in India and it will play a critical role in monitoring the proportion of the population exposed to the virus. But what is an ELISA-based antibody test and how is it different from RT-PCR tests? Here, News18.com explains.
WHAT IS AN ELISA BASED TEST?
Enzyme-linked immunosorbent assay (ELISA)-based testing is a laboratory technique used to detect antibodies produced by the body to fight foreign antigens or substances. ELISA-based tests are blood-based tests, which have high sensitivity and specificity. The sensitivity of a test refers to the percentage of results that will correctly determine the presence of infection in a person, and the specificity refers to the percentage of results that will correctly determine whether or not a person is infected.
According to the union health ministry, the ELISA-based antibody test developed by the National Institute of Virology, Pune, has a sensitivity of 92% and its specificity is 97%. The test involves drawing blood from the person. The sample is then placed into the small wells of an ELISA plate. These plaques are coated with the antigen or the inactivated form of the virus. If the blood contains antibodies, it binds to the antigen and a substrate solution is added to the well. The reaction usually produces a color change, so antibodies are detected. ELISA tests can be performed manually or semi-automatically and automatically.
WHAT DO WE KNOW ABOUT THE KIT DEVELOPED BY NIV-PUNE?
The ELISA-based test developed at the National Institute of Virology, Pune, is called the COVID KAVACH ELISA. The test kit has been validated at two sites and, as mentioned above, has high sensitivity and specificity, making it a better tool for surveillance of the spread of infection in a community compared to test kits. fast antibody. The test also has the advantage of being able to test 90 samples together in 2.5 hours, allowing laboratories to test many samples in one day.
It is an IgG Elisa based test. This means that the test will be done to detect the immunoglobulin G (IgG) antibody. The body produces immunoglobulin M (IgM) and IgG antibodies to fight against a pathogen. IgM antibodies are produced four to seven days after pathogens enter the body, while IgG antibodies are produced 10 to 14 days after pathogen appearance. If the IgG antibody is detected, it can be concluded that the person was exposed to SARS-CoV-2.
HOW WILL THE GOVERNMENT USE THE KITS DEVELOPED BY NIV-PUNE?
In an outline made public on Monday, the central government said ELISA-based test kits will be used as part of surveillance to monitor the prevalence and trends of SARS-CoV-2 infection at the district level.
The central government has said that surveillance and sero-surveys will be carried out in health facilities to verify the presence of the infection. This surveillance exercise will also provide information on possible community transmission throughout the country. The Ministry of Health has asked state governments and district administrations to collect 800 samples from one district per month as part of surveillance.
HOW IS IT DIFFERENT FROM RAPID ANTIBODY KITS AND RT-PCR TESTS?
ELISA is also a form of rapid test. However, other rapid antibody test kits are point-of-care and use a fingerstick method to draw blood. They take much less time and do not need a laboratory process to detect antibodies.
Both ELISA-based tests and point-of-care tests are not used to confirm Covid-19 infection and are only used for surveillance purposes. Those who test positive using these tests are usually tested with RT-PCR tests. RT-PCR tests are considered the gold standard to confirm the presence of SARS-CoV-2. RT-PCR is a time-consuming laboratory test that involves collecting