Coronavirus in Mumbai: Experts reiterate warning 
of overdependence on rapid antigen tests

Brihanmumbai Municipal Corporation (BMC) has conducted over a million rapid antigen tests (RAT) since they were deployed in July to augment the diagnosis of the coronavirus infection. Till now nearly 8,00,000 people have been tested for Covid-19 across Mumbai, of which 90,000 were tested through rapid antigen. Civic officials said to increase more numbers of Covid-19 testing they are procuring more one lakh new kits. Experts, however, continue to caution against overdependence as the antigen test is known to miss up to 50 per cent of infected cases.

Senior health officials confirmed that it will be the first test to be carried out in symptomatic patients coming to hospitals. “RT-PCR results still take about 24 hours to arrive, but antigen report comes in 30 minutes, which allows the hospitals to segregate the patient and begin treatment,” he said.

According to the BMC data, On Friday, 2,068 people were tested with rapid antigen and 191 were found to be Covid-19 positive with a 9.2% positivity rate. Until Friday, 89,126 people have undergone antigen testing, of which 5,674 have been detected with Covid-19. “The positivity rate of RAT is 6.3 per cent which is higher than the positivity rate of test conducted by RT-PCR and TrueNat which is 5.3 per cent,” said an official.

While RT-PCR is considered the gold standard for detection of the Sars-CoV-2 virus, which causes Covid-19, the rapid antigen test was allowed by the Indian Council of Medical Research (ICMR) in June to boost testing. Unlike RT-PCR, rapid antigen tests give results within 30 minutes. They come with a rider, though, of higher false negativity and can miss up to 50% cases. Due to the lower accuracy, the ICMR advises its use in symptomatic patients or in containment zones.

“We are constantly focusing on more number of tests so that every suspected case is detected and provided treatment. This will further reduce the spread of infection. With aggressive and focussed testing, we have been able to reduce fatalities in the past two months and plan to bring down the fatality rate further,” said a senior health officer from BMC.

Meanwhile, BMC is in the process to procure more 1 lakh kits, of which 50,000 have been received, while the rest is likely to be acquired in the next two days. “The main reason to procure 1 lakh antigen kits is to increase Covid-19 testing. We will provide the testing kits to civic-run dispensaries and maternity hospitals to run the test. For that, we placed the second order to procure another branch of 50,000 kits,” said Suresh Kakani, additional municipal commissioner, BMC.

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