The institute has developed enzyme-linked immunosorbent assay (Elisa) which can help detect antibodies developed in response to the coronavirus infection. Health minister Dr Harshvardhan informed this is the first test of the kind to be developed in India and it will play a critical role in surveillance of proportion of the population exposed to the virus.
This kit was tested at two sites in Mumbai and has high sensitivity and accuracy. The minister added that Elisa-based testing is easily possible even at the district level. Now, the test kits have been transferred for mass production to Zydus Cadila.
Here is more about the Elisa-based testing and its importance in dealing with the Covid-19 outbreak.
What is ELISAs test?
Typically, the Enzyme-Linked Immunosorbent Assays (ELISAs) based test helps in detecting antibodies that are produced by the body to fight against antigens or foreign substances.
It is a blood-based test with high sensitivity and specificity. Here the word sensitivity means the percentage of results that will detect the presence of infection in a person and specificity refers to the percentage of results that will 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 per cent and specificity is 97 per cent. The sample of the blood collected is placed inside the small wells of an ELISA plate. These plates are coated with the antigen or the inactivated form of the virus. In case the blood contains antibodies it binds to the antigen and a substrate solution is added to the well. If the reaction produces a color change it indicates antibodies. The tests can be done manually or in a semi-automatic and automatic way.
How are the kits developed by NIV-Pune able to determine antibodies?
The Elisa-based test kit is better known as COVID KAVACH ELISA. The test kit has been validated at two sites with high sensitivity and specificity which can help determine the spread of Covid-19 infection in a much better way compared to the rapid antibody test kits. Another advantage over other test kits is that it can evaluate 90 samples together within 2.5 hours, allowing labs to study more samples in a day.
What does it actually determine?
It is basically an IgG Elisa-based test which is conducted to detect the Immunoglobulin G (IgG) antibody. Our body produces Immunoglobulin M (IgM) and IgG antibodies to fight against a pathogen. The IgM antibodies are typically produced in four-seven days after pathogens enter the body while the IgG antibodies are produced between 10-14 days of the pathogen's appearance. If the IgG antibody is detected, it can hint that the person has been exposed to SARS-CoV-2.
How the government intends to use it?
The government has said the 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 government will be conducting health facility-based surveillance and sero-survey to check the infection. It will help in getting insights related to community transmission across the country. According to news reports, the health ministry has asked state governments and district administrations to collect 800 samples from a district per month as part of the surveillance.