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India testing over 5 lakh per day, but over-dependence on antigen tests leading to more missing cases

It means that asymptomatic individuals who show negative through antigen test, simply fall through the crack and may keep spreading the disease in the community unknowingly.

Published: 27th July 2020 06:10 PM  |   Last Updated: 27th July 2020 06:21 PM   |  A+A-

Health workers wearing PPE hold samples for COVID-19 rapid antigen testing in Sonitpur district of Assam on Tuesday. (Photo | PTI)

Express News Service

NEW DELHI: India, on Sunday, reached a significant milestone of carrying out over 5 lakh tests in a day to detect new Covid-19 tests amid concerns that the majority of these tests are antigen tests- that miss a large number of positive cases.

The Indian Council of Medical Research, on Monday, said that 5, 15, 472 tests were conducted on Sunday.

As a total of 49,931 fresh cases were detected during the same period, taking the total number of confirmed infections to 14,3 54, 53 -- this means that India’s test positivity rate on Sunday was about 9.7 per cent.

So far, 1,68,06,803 samples have been tested in the country.

The real problem in tackling the pandemic in India as of now, public experts point out, is that states are increasingly using antigen tests which owing to comparatively low sensitivity, or ability to detect the presence of the virus in an infected person, as compared to gold standard RTPCR test, which misses nearly half positive cases.

The council’s testing guidelines say that the tests carried out on suspects should be antigen tests first and those who test positive should be treated as true positive and be dealt with according to their clinical symptoms. However, it says, only those who have symptoms but are negative on antigen tests should be followed with RTPCR tests to further assess them.

It means that asymptomatic individuals who show negative through antigen test, simply fall through the crack and may keep spreading the disease in the community unknowingly.

This approach, most believe, is deeply problematic.

“While the antigen test has a high specificity, its sensitivity is just 40-50 % in the real world,” said researcher and senior doctor at Medanta hospital in Gurugram. “This means if one is antigen test negative, one still has to rule out Covid by RTPCR. However, if the antigen test is positive, that confirms COVID-- so ideally, RTPCR testing rather than antigen test should be ramped up.”

The ICMR however has not been sharing information on the break of tests being carried every day. A message seeking response on Sunday’s figure by this newspaper has remained unanswered.

Public health researcher Oommen C Kurian said that while every Sunday till last week, used to see a big decline in testing numbers, it was good to see the country' s Covid response overcoming that big handicap, with a big surge in testing this Sunday.

“Assuming that those symptomatic cases missed by the antigen tests are also tested by RTPCR, this need not lead to delay in treatment necessarily,” he said. “However, it may miss a number of asymptomatic cases, and that is a concern.”

Kurian reckoned that the government's shift may be understandable since the focus seems to be on reducing the pace of the spread quickly and reducing deaths, rather than finding every positive case and "eradicating" the virus.

“I think this is the closest we will ever get to an open admission of community spread by the government,” he said.

Some epidemiologists however said that too much emphasis on testing and contact tracing was not practical given our limited resources.

“Also, testing, tracing, and isolation are important in the beginning or during the end of a pandemic but I am afraid we are far from both,” said Dr. Amitabh Banerjee who teaches community medicine in a medical college in Pune.

“Our focus should, therefore, be on saving lives and giving hospital care to those who need it.”

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