2,000 people to be covered in second serological survey in Gurugram

A serological survey is a tool used by the epidemiologists to study the prevalence of an infection within a community.

To expedite the process tracing the prevalence of Covid-19 infection in Gurugram, the state health department has planned to expand the coverage of the second round of serological survey. The test, which helps to check undetected community transmission, will now be conducted among 2,000 people to check the presence of Covid-19 antibodies in their blood serum. The state health department officials are presently working on the details of the survey but said that the survey will start as soon the plan is ready.

A health worker in PPE kit conducts rapid antigen Covid-19 tests, at Sukhrali Village Community Centre, in Gurugram. (Parveen Kumar/ Hindustan Times)

A serological survey is a tool used by the epidemiologists to study the prevalence of an infection within a community. Officials of the health department said the survey will cover people from different backgrounds, including cab drivers, people working in malls and shopping complexes and other sections of the vulnerable population, as per the guidelines of the Indian Council Medical Research (ICMR).

“The sample size of the serological survey is being increased to 2,000. It will involve the use of 278 antibody kits that are yet to be utilised from the previous stock of 460 kits,” Dr Virender Yadav, chief medical officer(CMO), said.

The district health department conducted the first round of serological survey on June 24 at the CMO office in the old Civil Hospital. At least 182 blood samples were collected mostly from police personnel, healthcare workers, etc. A total of 32 people tested positive for the SARS-CoV-2 antibody. “A detailed plan will be prepared by the health department this week to conduct the survey in different parts of the city,” said Yadav.

Following the Indian Council of Medical Research (ICMR) guidelines on the serological survey, 20 categories, such as immunocompromised patients, healthcare workers, industrial workers, aviation staff, taxi and auto drivers, prisoners, staff members of urban local bodies (ULBs) and persons working with banks, post offices, couriers and telecom companies, among others, will be covered. A few other sections, such as preoperative patients, pregnant women and elderly people have also been included by the state government in the survey. Yadav said that these people will be covered in both containment as well as non-containment zones across the city.

The survey will involve the use of an improved Enzyme-Linked Immunosorbent Assay (Elisa)-based antibody kit. The IgG ELISA test has been approved by the ICMR because of it of its high sensitivity and specificity. Al least 50% of the kit will be used on patients, who have been tested positive within the last two weeks. The remaining kits will be used on those who have no history of contracting the Covid-19 infection.

Studies show that the IgG antibodies start appearing after two weeks of the onset of infection. Even if the patients have recovered, the antibodies can last for several months. To conduct the test, the five millilitres of blood is collected, which is then separated into blood and plasma. The plasma is used to detect the antibodies developed against the SARS-CoV-2 virus. The IgG test is not useful for detecting acute infection but indicates episodes of Covid-19 infection in the recent past.