ICMR antibody survey begins, results likely in three weeks
The Indian Council of Medical Research (ICMR) has collected around 24,000 blood samples from 60 districts across 21 states over the past two weeks for a serosurvey to check for exposure to SARS-CoV-2, which causes coronavirus disease (Covid-19), among the country’s adult population.
The cross-sectional survey of adults, aged 18 years or more, will detect infection in the community by testing for the presence of antibodies against SARS-CoV-2 that are found in the blood of people who have recovered from it.
Four representative samples were collected from 60 districts on the basis of reported Covid-19 cases per million population -- zero, low (0.1-4.7), medium (4.8-10), and high (>10). Around 400 samples from 15 districts from each category were selected randomly, according to ICMR.
The first batch of about 70% of samples was dispatched to a central laboratory in Chennai for analysis on Sunday, and the results are expected in about three weeks. “The ICMR-National Institute for Research in Tuberculosis in Chennai will do the analysis,” said an ICMR official, requesting anonymity.
This community-based survey will hold the key for getting several vital clues on the viral disease such as its trend, testing pattern, etc, according to experts. “If more people have antibodies and were never detected that means the infection is widely present. It’s a good thing that only a few are suffering from complications leading to deaths. This is also an indirect methodology to ascertain whether enough tests are being conducted across the country,” said Dr. Girdhar R Babu, head, Lifecourse Epidemiology.
The blood samples will be tested for detecting IgG antibodies using ELISA method (IgG is an antibody that develops later as compared to the other antibodies, hence, determine a past infection. Elisa method is an enzyme-based laboratory test that detects and quantifies antibodies in the blood) that will determine a past infection due to the virus.
Andhra Pradesh, Assam, Bihar, Chhattisgarh, Gujarat, Jharkhand, Karnataka, Kerala, Madhya Pradesh, Maharashtra, Odisha, Punjab, Haryana, Rajasthan, Tamil Nadu, Telangana, Uttar Pradesh, Uttarakhand, Himachal Pradesh, West Bengal, and Jammu & Kashmir are the 21 states from where samples have been collected.
Besides, about 5,000 samples have been collected from 10 hot spot cities that have reported the maximum caseload such as Mumbai, Delhi, Chennai, Ahmedabad, Thane, Pune, Indore, Kolkata, Hyderabad, and Aurangabad.
“Conducting population-based serosurveillance for SARS-CoV-2 will estimate and monitor the trend of infection in the adult general population, determine the socio-demographic risk factors and delineate the geographical spread of the infection,” said a recently-published ICMR document on serosurveillance.
“Such serosurveys repeated at regular intervals can also guide containment measures in respective areas. State-specific context of disease burden, priorities and resources should guide the use of multifarious surveillance options for the current Covid-19 epidemic,” the paper said. “We’re likely to repeat the survey later depending on the results,” said the ICMR official.
Apart from the serosurvey, the Union Ministry of Health & Family Welfare (MoH&FW) has a hospital-based active surveillance plan using real-time polymerase chain reaction (RT-PCR) among healthcare workers, outpatient department patients, and pregnant women in all the districts in the country. At least 10 hospitals -- six public and four private hospitals -- will be selected from each district for the sampling, with an overall target of collecting 800 samples a month.
These two surveys are in addition to conducting a random test of about 250 severe acute respiratory infection (SARI) and influenza-like illness (ILI) cases that the Centre has advised all the states to carry out in each district.