Rapid Antigen Kits Helped India Test More People For COVID, But Their Reliability Is A Concern
Over the past few weeks, India has stepped up the capacity to conduct more COVID-19 tests and Monday, a single-day record of 6.6 lakh tests were conducted across the country
On Tuesday also more than 6.19 lakh COVID-19 tests were conducted in India taking the overall tests in India so far over 20 million.
And a large portion of these tests is Rapid antigen tests (RAT).?The Indian Council for Medical Research (ICMR), said on Tuesday that RAT made up around 25%-30% of the tests conducted in India.?
"When we started, antigen tests comprised only 5-6 per cent of the total tests being conducted in a single, but this proportion is consistently rising. Today, total antigen tests are nearly between 25-30 per cent tests of the total number of covid19 tests done so far," said ICMR Director-General Dr. Balram Bhargava said.
While the rapid tests produce results quickly, sometimes in less than an hour, it has low sensitivity, meaning that it can also miss many who could be COVID-19 positive.
Dr Bhargava said that rapid antigen detection test has a very high specificity, i.e., its ability to detect true negative from 99.3 to 100 per cent. However, it has moderate sensitivity between 55 to 85 per cent.
"This means that--about 45-15 per cent of the positive cases could be getting missed. And that is why we have reiterated in our advisory that if the person is symptomatic, the rapid antigen test results are negative then it should be followed by RT-PCR test to confirm the diagnosis," Bhargava said.
When asked about what are chances of asymptomatic cases getting missed out, Bhargava said once the virus enters the body, it takes about five days for the person to manifest symptoms of fever. "From 0 day to 5 day, you may not have any symptoms. And that point of time, even the RT-PCR tests may be negative and even the antigen test is also negative. So that problem is there."
"Once I get the fever, then we expect the test will be positive whether it is by antigen test or RT-PCR test, from that perspective both are similar. From 0-5 day one may not have any symptoms and at that point of time even the RT-PCR and antigen test may be negative," he explained.
Regarding the number of asymptomatic people and what percentage that varies and it ranges between 20 to 28 per cent, said Dr Bhargava pointed out a paper published in Indian Journal of Medical.