Serological survey in Gurugram: Of 362 people tested, 49 found with antibodies

As of Thursday, the health department has tested a total of 362 people as part of the ongoing serological survey to ascertain the prevalence of Covid-19 among the

As of Thursday, the health department has tested a total of 362 people as part of the ongoing serological survey to ascertain the prevalence of Covid-19 among the district’s population. Of these, 49 people were found to have developed antibodies necessary to stave off repeat infection by the SARS-Cov-2 virus, said health department officials. A serological survey is an epidemiological tool used by health department officials to find out the prevalence of Covid-19 within communities.

HT Image

“A total of 362 people were tested for antibodies using IgG enzyme-linked immunosorbent assay(Elisa) kits. Of them, there were 24 people who had already been confirmed positive by a reverse transcription-polymerase chain reaction (RT-PCR) test earlier. As per the guidelines issued by the Indian Council of Medical Research (ICMR), confirmed positives also need to be tested to see if they have developed antibodies or not. Out of the remaining 338 tests conducted on subjects whose history of infection was unknown, 25 people had a seropositive diagnosis,” said Dr Ram Prakash Sharma, district epidemiologist, Gurugram.

“This is a good sign, especially since the samples were collected largely from areas, such as Dundahera, Sirhaul, Pataudi, and others, where there have been a large number of positive cases. A significant portion of the samples were taken are from local shopkeepers, who come into contact with lots of people daily,” said Dr. Virender Yadav, chief medical officer (CMO), Gurugram. He added that serosurveillance is going to become a routine practice in the coming weeks, with at least 400 tests to be conducted every month, as part of a larger, nationwide effort by the Indian Council of Medical Research (ICMR) to understand the prevalence of Covid-19 in communities.

Serological surveys make use of Elisa tests, and are conducted to estimate the proportion of a population which has been exposed to SARS-CoV-2 infection. “As of now, the results from preliminary antibody tests show that while there are undetected cases in Gurugram, the extent of the spread is not so much as we had initially feared,” said Dr. Prakash, adding that a wider sample, of about 2,000 people, would soon be tested for SARS-Cov-2 antibodies. “That should confirm more strongly that we have been able to prevent large-scale community transmission,” he added. The district health department is currently working on a plan to extend the coverage of the serological survey to 2,000 people.

Experts, however, said that a sample size of 360 people for Gurugram, which has an estimated population of about 25 lakh people, is too small to give an accurate picture of what the prevalence of Covid-19 really is. Dr. Prabhakaran Dorairaj, vice president (research and policy) at the Public Health Foundation of India, said, “Even if the right kinds of subjects are selected, it will not adequately represent the whole of Gurugram’s population. If the goal is to get a correct picture of prevalence, then the department must first classify the district into two areas: old Gurugram and new Gurugram. Within these areas, you have to use socio-economic data at the ward level and census enumeration block level to create a sample representative group of the larger demography of the city. That will tell you how prevalent the disease really is in Gurugram,” he added.