Positive antibody tests not proof of immunity

Mumbai: The antibody tests used to check if a person has developed immunity to Covid-19 infections may not be helpful 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. Gangakhedkar is one of the key members of ICMR driving India’s Covid-19 strategy. “There islack 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 ₹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.

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 RT-PCR tests, the scientist said there were several reasons, including if samples are taken incorrectly, low viral load, patients who are asymptomatic and samples not being tested within 72 hours.

There are numerous diagnostic challenges, and India has coped with them well over the last five months, said Gangakhedkar.