By Economic Times – Antibody tests to check immunity to SARS-Cov2 lacks evidence: Raman Gangakhedkar MUMBAI: The antibody tests used to check if a person has developed immunity to Covid-19 infections may not be helpful to use as “immunity passports” by individuals as there is lack of clarity on long term immunity against the disease, according to Raman Gangakhedkar, the head of epidemiology and communicable diseases at the Indian Council of Medical Research.

Gangakhedkar’s statement came during a webinar organized by the National Cancer Grid, in a presentation on the evolution of the testing protocol of the government for the virus outbreak. Gangakhedar is one of the key members of ICMR driving India’s Covid-19 strategy.

Antibody tests are blood-based tests which detect the presence of antibodies that human beings generate to counter an infection. Regulatory agencies do not recommend the use of antibody tests for diagnosing Covid-19 because these tests do not show the presence of active infection. It only gives an indication whether a person has been previously exposed to the virus. In the context of SARS-Cov2, the formal name for the virus, these tests detect the presence of proteins/antibodies called Immunoglobulin M (IgM) and Immunoglobulin G (IgG).

“There is a lack of clarity if these tests can be used as immunity certificates because we lack evidence,” said Gangakhedkar, adding that ICMR has capped the rates for these kits at Rs 214.

In a revised testing criteria note on June 23, ICMR suggested that government organizations, private hospitals and offices can perform antibody testing on their staff as this will help in allaying the fear and anxiety of health care workers, office employees etc.

Following the advisory, the Maharashtra government too issued a notification saying organizations could use antibody tests on those employees returning to work.

The idea of using antibody tests on employees has been debated across the world and countries including Germany, Chile and the United States have decided to deploy these tests in order to get those who have recovered or become immune to the virus back to work. However, the data on how strong the immunity lasts is not yet clear.

On the evolution of testing in India, Gangakhedkar said that the National Institute of Virology lab in Pune started doing Reverse Transcription Polymerase Chain Reaction (RT-PCR) tests from January, but the test load then was erratic.

On concerns over false negatives thrown up by the RT-PCR tests, the ICMR scientist said there were several reasons for the false negatives, including if samples are taken incorrectly, low viral load, patients who are asymptomatic (they have low viral load) and samples not being tested within 72 hours and not stored in minus 70 degree temperatures.

There are numerous diagnostic challenges, and India has coped with them well over the last five months, said Gangakhedkar, adding that since it is an evolving outbreak with changing evidence, one needs to look for newer evidence and guidelines to offer quality care and diagnosis.
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