Six months into a pandemic and well into its sixth iteration, India’s Covid-19 testing strategy is still a work in progress.
As of 5 September, India had conducted over 49 million tests for the virus. What this massive figure obscures, however, is which tests have allowed the country to ramp up its testing numbers. The Indian Council for Medical Research (ICMR)—the government body spearheading the Covid-19 response—released an app to every testing centre and lab to register every test conducted. But the breakup of what sort of testing has been done is not in the public domain.
The problem is that, while increasing testing is critical, not all tests are created equal. On one hand, you have the rapid antigen tests. These offer faster results, and are cheaper and easier to administer. These can detect the presence of the virus in under 45 minutes.
There is a flip side to this convenience. Rapid antigen tests are less accurate than the ‘gold standard’ of Covid-19 testing—reverse transcription polymerase chain reaction, or RT-PCR, tests. Considerably more expensive than their quicker counterparts, they take between two to four days to show results.
While the split between the two types of tests remains unknown, in an August press briefing, Balram Bhargava, director general of ICMR, offered a glimpse under India’s testing hood. He stated that up to 30-35% of all tests conducted were through the newer rapid antigen test technology.
The prevalence of antigen testing should raise a massive red flag. According to the ICMR’s own evaluation, these tests have accuracy rates between 50.6% and 84%. On the lower end, this would mean that they could miss one in every two Covid-positive cases.
Consequently, big private lab chains have refused to use antigen tests, while both Tamil Nadu and Rajasthan have doubted their accuracy. Despite this, the national task force to fight Covid-19 continues to include rapid antigen tests in its latest testing advisory for lack of a better alternative.
The follow-up testing required to counter the lack of accuracy among antigen tests has largely not happened.
It took repeated orders from the Delhi High Court for the nation’s capital to share follow-up data of those who were tested using antigen tests. In response to a petition that sought transparency in testing data, Delhi’s health department revealed that 281,555 rapid antigen tests were conducted between 18 June and 15 July. Only a fraction of those who tested negative—1,365 people out of 262,075—were put through RT-PCR testing later. Even in such a small sample, nearly one in five of these cases turned up positive.
The situation in Delhi is indicative of a wider problem.