There were close to 650,000 tests for Covid-19 across India on Thursday and the average number of daily tests in the last week of July is more than twice of what it was in beginning of the month, according to government data and an analysis by HT, suggesting the country was on track to reach the million-tests-a-day threshold.
As on Friday, India has had 1.69 million cases of the coronavirus disease that has led to 36,549 deaths, making it the third hardest-hit nation after the United States and Brazil, where 155,000 and 91,000 fatalities have respectively taken place.
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India has till now carried out close to 19 million tests but will need to ramp up this process further in order to better detect and head off new outbreaks. India’s per million tests as on July 30 comes to about 14,129, a number that has improved from 6,794 on July 1 but is still among the lowest in the world since it has the world’s second-largest population.
The roughly 19 million tests is equivalent to 1.5% of the population.
Ramping up testing was among the issues discussed by Union health minister Harsh Vardhan on Friday during the meeting of the Group of Ministers (GoM) on Covid-19. “The measures to be taken include revamping the strategy for effective management of containment zones through stricter perimeter control; widespread rapid antigen tests; intensive and rapid door-to-door search…,” said the health minister.
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The antigen tests the minister referred to has emerged as key to India’s disease surveillance efforts – the test takes at most 30 minutes and costs nearly a fifth of the lab tests, which can take at least a day for results to show but is largely seen to be more reliable.
The strategy will be crucial to detect new hot spots that are now believed to be emerging in Andhra Pradesh, Karnataka, West Bengal and Uttar Pradesh – away from the previous infection hotbeds of Maharashtra, Delhi and Tamil Nadu.
Arunachal Pradesh, Tripura, Sikkim, Telangana, Gujarat, UP and Kerala are among states that have recorded the biggest improvement in weekly testing numbers. Arunachal’s numbers were up 622% while UP’s rose by 257%.
On the other hand, Bihar, West Bengal, Madhya Pradesh and Karnataka recorded some of the slowest growth in daily testing.
Indian Council of Medical Research (ICMR) data suggests the increase has largely been due to antigen tests, which were rolled out on June 14 and now account for 10% of all tests conducted. In the past one month, antigen tests have increased to account for about 25% of the tests performed per day across India.
These tests are the only other option besides the real-time reverse transcription polymerase chain reaction (rRT-PCR) test, which is considered the gold standard to diagnose Covid-19.
An antigen is a protein (in this case present on the virus) that induces an immune response in the body in the form of production of antibodies against a disease, and detecting its presence through an antigen-based test determines a present infection.
This sort of test has been seen as key to the turnaround in Delhi, where the positivity rate of tests — the proportion of people who are found positive for the disease from among those tested – dropped from 37% a month ago to about 6%. Changes in positivity rate can indicate whether a city or a state is able to identify all of its cases.
But in case of antigen tests, ICMR guidelines say, all symptomatic negative cases have to be confirmed through an rRT-PCR test to rule out a false negative.
Virologists and microbiologists say mass testing is the key to identify and isolate those infected so that the disease doesn’t spread.
“The way ahead is to test as many people as possible, to be able to track and isolate those people who are infected so that the disease spread is contained. If you isolate them in time, the spread in the community will be curtailed,” said Jacob John, former head, virology department, Christian Medical College, Vellore.
Dr Amita Jain, head, microbiology department, King George’s Medical University, Lucknow, said: “Since positive results are confirmed positives, it will work in picking up cases, even if it is not able to pick up all cases. In areas where the viral load is very high it should work well, and that’s what we want — that cases are tracked early. RT-PCR is a better test but can’t be deployed on mass scale as it’s not only cumbersome and expensive but also takes much longer. It’s ok to conduct confirmatory negative tests through RT-PCR.”
Delhi was the first state to start antigen based Covid-19 testing last month, and other states that have deployed antigen testing in a significant way include Maharashtra, Gujarat, Karnataka, Telangana, Uttar Pradesh, Punjab and some north-eastern states.
Antigen testing, however, has not picked up in the private sector. Officials in several hospitals said they do not use it as a first choice because of the need for an rRT-PCR to confirm a negative result.
“Might as well do an rRT-PCR test to diagnose a case rather than do a rapid antigen test and confirm it with using an rRT-PCR. It will also mean double the cost for a patient when we can know their Covid status with a single test,” said an administrative official in a prominent private hospital.