NEW DELHI: The Indian Council of Medical Research, on Saturday, asked states to carry out extensive serosurveillance to estimate the population exposed to SARS CoV-2, the pathogen that causes COVID-19, using IgG ELISA antibody tests in their respective territories.
The suggested state level survey is in addition to two surveillance exercises the agency has already undertaken to test samples collected from 70 districts, including 10 hotspot districts, and some hospitals in all districts of the country.
Now, ICMR has specified nearly 17 categories of people: immuno-compromised patients, all healthcare workers, prisioners, bankers, mediapersons, people working at airports, industrial workers, staff in municipal bodies, vendors, drivers, migrant labourers and police and security personnel among others, that should be tested to check whether they have antibodies against the virus.
An ICMR official explained that states can design their own surveys based on their own assessment and seek technical help from the agency wherever required in conducting and interpreting them.
“Since the antibody tests cost just about Rs 300 it should not be very difficult for states to carry out large scale surveys,” he told The New Indian Express.
Issuing the advisory, ICMR said that while real-time RTPCR test is considered gold standard for clinical diagnosis of SARS-CoV-2, the test is useful only when performed in the acute stage of infection.
Adding that for several viral infections, antibody tests are useful for disease detection after 5–7 days of illness, the council said that IgG antibodies generally start appearing after two weeks of the onset of infection, once the individual has recovered after the infection and last for several months.
“Therefore, the IgG test is not useful for detecting acute infection but indicates episode of SARS-CoV-2 infection in the past,” it said to the states underlining that detection of IgG antibodies is useful in serosurveys help understand the proportion of population exposed to SARS-CoV-2 infection including asymptomatic individuals and survey in high risk or vulnerable populations.
“Depending upon the level of sero-prevalence of infection, appropriate public health interventions can be planned and implemented for prevention and control of the disease. Periodic sero-surveys are useful to guide the policy makers,” the advisory added.
Scientists at ICMR-NIV had developed and validated an indigenous IgG ELISA test for antibody detection for SARS-CoV-2 which are now being produced on mass scale by at least 7 companies.
States can also choose to use other imported or locally manufactured testing kits approved for use in the country, the apex health research body said.