A health worker wearing personal protective equipment collects a swab sample from a resident at a Covid-19 test site in the courtyard of a school in New Delhi, India on August 2.
Photographer: T. Narayan / Bloomberg
Photographer: T. Narayan / Bloomberg
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India’s offer to control its emerging viral infections by increasing the use of rapid but less sensitive testing could actually make things worse for the South Asian nation.
With one of the fastest growing epidemics in the world, but also one of the lowest test rates, India began using rapid antigen testing in late June to increase detection. But the tests, which can report false negatives as much as 50% of the time, threaten to obscure the true picture of its outbreak, and contain efforts to further challenge.
Between 25-30% of the country’s daily tests now are rapid antigen tests, Balram Bhargava, the director general of the Indian Council of Medical Research, told reporters at a briefing in New Delhi. It was the first time that India’s leading research team had broken down the test data – the ICMR website does not yet specify what type of tests are done in its daily data.
In some cities like the capital of New Delhi, the rapid test numbers are even higher – the latest data as of August 12, showed the city 12,422 rapid antigen tests and 6,474 of the more sensitive real-time polymerase chain reaction tests.
Confidence in these tests casts even more doubt on Prime Minister Narendra Modi’s ability to quell the epidemic, which is now growing indefinitely through the nation’s hinterland. It could also mean that the declining case numbers seen in the big cities may be due to false negatives, raising questions about whether infection is really being curtailed.
Worse, the use of rapid testing could allow some infected people to return freely into the community, and spread the pathogen to even more people. In the In the Philippines, a large number of false negatives on tests performed on returning workers meant that infections were sown in new places when they were allowed to go home, causing a sharp resurgence of cases.
The Indian Ministry of Health did not respond to an e-mail and phone call seeking comment.
Most other countries with major outbreaks such as the United Kingdom and the US use the RT-PCR tests that detect the genetic material of the virus. While experts say rapid antigen testing can help countries detect outbreaks quickly where hot spots are, India’s practice of confronting the data of rapid testing and traditional RT-PCR units is at risk of hiding their true infection picture.
Other tests, such as those for serological studies or testing of high-risk groups for antibodies, are counted separately. The FS, whose test protocol was recently beaten by Microsoft Corp. founder and billionaire philanthropist Bill Gates, has failed scale up its testing facilities to push through as many tests as it needs to.
‘I do not think it is good science to put the two tests together. “If the rapid antigen tests are only 50% sensitive compared to PCR tests and there is a very high prevalence of community transmission, then they are not very good test,” said Peter Collignon, a professor of clinical medicine. Australian National University Medical School. “Flipping a coin can be almost as good.”
Shifting Strategies
The faster test itself is not the problem. Rapid antigen testing is considered a competitive strategy to test broadly – it is faster, cheaper and requires less complex technology than molecular testing. The rapid tests cost about 450 rupees ($ 6) compared to the molecular tests, where the government has covered the price at 2400 rupees.
“The basic entry should be to test as broadly as possible, but report results separately for RAT and RT-PCR so that trends can be studied in each separately,” said Prabhat Jha, professor of Global Health and Epidemiology at the Dalla Lana School of Public Health , University of Toronto.
In Asia, the countries that have had the most success in controlling their infections, such as China and South Korea, do not use the rapid tests much, because they scale up their molecular testing capacity early.
De World Health Organization guidance, unchanged since April, has been to use the more accurate PCR tests.
A person wearing a face mask looks inside a test car where health worker performs rapid anti-methodology Covid-19 tests at a health center in New Delhi on July 27.
Photographer: T. Narayan / Bloomberg
Opaque data
India’s clubbing along with its various types of tests is part of the nation’s bigger problem with opaque data and one that experts say is hindering its pandemic fight.
Chief Minister of Delhi Arvind Kejriwal has suggested that the capital moves to an immunity to herd serological survey last month found antibodies in 23% of the samples examined. Experts warn that this is an unreasonable projection, especially considering the short press release has given brief details about the tests themselves.
The results of a similar survey, with anti-antibody test, previously conducted by the ICMR have yet to be released.
Jha is of the opinion that the details of the antibody test in Delhi should be published for independent scientific control and described the suggestion that herd immunity is being developed as “scientifically suspect.”
“The key here is not the test. It is reporting and sharing data on individual records (protection of confidentiality) and also saying that Singapore did so, “Jha said in an email.” Without open data, India will struggle more to contain the virus. “
– With the help of Tim Loh
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