New Delhi, Jun 30 (IANS): With the National Centre for Disease Control (NCDC), under the Ministry of Health and Family Welfare, beginning the 14-day serological survey across Delhi to ascertain the presence of antibodies among people, experts say that the survey will help in gathering details on spread of the viral infection in the community, and also help in identification of community transmission.

NCDC Director Sujeet Kumar Singh said the serological survey will help gather details on the prevalence of the viral infection 15 days prior, and also ascertain the presence of antibodies among the people.

Blood samples from 20,000 persons will be tested, under this survey, which is part of the Centre's support to states and Union Territories to combat Covid-19. Currently, Delhi has reported 85,161 coronavirus cases so far and 2,680 people have succumbed to the viral infection.

The Indian Council of Medical Research (ICMR) has approved antigen-based rapid tests and supplied 50,000 such rapid test kits to the Delhi government. "ICMR has provided all these test kits free of cost to Delhi," the Health Ministry had said. According to the ministry, ICMR has supplied diagnostic material for carrying out 4.7 lakh RT-PCR tests to the 12 functional labs in Delhi.

Arvind Kumar, Chairman Centre for Chest Surgery and Director in Institute of Robotic Surgery at the Sir Ganga Ram Hospital, said the survey is being done to gather information on how many people have suffered from the disease and developed antibodies, or the level of immunity in the community.

"How much involvement of the community has taken place or the extent of community transmission? For example, if 1 lakh people are tested and only 3 per cent are tested positive, then it is not an issue, but if 30 per cent or more are tested positive then it would be apparent the viral infection has spread in the community. The serological survey is part of assessment in pandemic to understand the extent of spread in the community," he said.

Vikas Maurya, Director, Department of Pulmonology and Sleep Disorders at Fortis Hospital, said the survey will help in identifying whether patients have developed antibodies, especially in the containment zones.

"Although, guidelines for the serological survey were introduced by ICMR earlier, the rapid test kits were not available then. The problem with rapid tests is that positivity comes after 6 to 7 days, but it's cheaper. Through this survey, people who are not going for testing can be tested. It will help in identifying prevalence of the disease in the containment zone," he added.

Dr Poonam Das, Chief of Pathology, Max Labs said that sero-surveillance involves a blood test and indicates the presence of IgG antibodies, and it does not indicate a current infection.

"This test cannot be used for diagnosis of Covid-19 or monitoring of Covid positive patients. This only tells us if someone has been Covid positive in the past or not. Rapid antigen test is a naso-pharangial swab test. This test detects infection in asymptomatic/symptomatic patients. This is a quick test (2 hrs) and is a lot cheaper. However, when carried out in symptomatic patients, a negative result has to be further confirmed by the gold standard RT-PCR test," she added.