The Indian Council of Medical Research is conducting a household-level antibody testing of 24,000 adults in select districts to “estimate the prevalence of (Covid-19) infection” among people. This new research comes on the heels of another facility-level pooled testing of all districts of the country. Both mark an enhanced level of testing surveillance from previous studies focused on Severe Acute Respiratory Illness (SARI).
“This is a household-based survey of adults to look for presence of infection across the country in a systematic manner irrespective of reporting of cases currently. It will look for presence of IgG antibodies that usually appear 10 to 14 days after infection,” ICMR researcher Dr Tarun Bhatnagar told The Indian Express.
He said SARI surveillance is a separately ongoing testing of hospitalised patients using RTPCR test that goes on as part of routine testing to detect new coronavirus cases.
Immunoglobulin G, or IgG, is a common type of antibody, which protects the body against infection.
The sample group is spread across 69 districts, covering four different district strata categorised by their case count. In each district, 400 random households in 10 clusters will have one adult individual tested for Covid-19 antibodies in what is called a “sero survey”.
This test result reveals if an individual has had Covid-19, although the efficacy of antibody tests has been put into question.
In a separate, recently announced study, individuals from all districts of the country will be randomly tested.
In each district, 10 health facilities — six public and four private — will select 100 healthcare workers, 50 outpatient attendees who do not have influenza-like illness, and 50 pregnant women to undergo RT-PCR and antibody tests.
In the last ICMR research study on syndromic SARI surveillance, released April 18, out of 5,911 SARI patients randomly tested for coronavirus from February 15 to April 2, a total of 104 (1.8 per cent) tested positive for the virus across 52 districts in 20 states and Union Territories.
The percentage of random positive samples of Covid-19 among SARI patients across the country showed an increase incrementally over this period. On March 20, the SARI surveillance was expanded to include all SARI patients, not only random sampling.
The study also found 36 districts in 15 states with cases that had no history of contact with a known case, or any international travel. “These districts need to be prioritized to target COVID-19 containment activities,” the research stated.
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