Rapid antigen test more reliable than RT-PCR, say experts
Sero survey to bring forward true rate of infection, fewer cases expected by July-end
Published: 26th June 2020 09:31 AM | Last Updated: 26th June 2020 09:31 AM | A+A A-
A healthcare worker sprays disinfectant on an ambulance at Shakur Basti Covid isolation centre in New Delhi on Thursday | Parveen Negi
NEW DELHI: With the introduction of rapid antigen tests (RAT) in the national capital, the count of daily samples collected over the past week has increased drastically. A total of 1,16,710 tests combining both RT-PCR and RAT were conducted in the national capital over the past week.
However, according to the Delhi government’s response to the high court, the number of RT-PCR tests conducted has gone down. As per protocol, if a person is tested positive using RAT, the individual will once again have to undergo an RT-PCR test.
Experts though claim that under the current circumstances, rapid antigen testing is more reliable as the sensitivity is around 80 per cent and specificity is 100 per cent. “RT-PCR will have its limitations and since more tests are required to be conducted on a mass level, rapid antigen is fine to go ahead with,” said Dr MC Misra, former AIIMS director.
“Antigen tests give results faster and are equally cost-effective, which is not in the case for RT-PCR... Both the tests are based on ‘antigen’, which is similar. However, if someone is diagnosed positive, it can be false in both cases,” added Dr Jugal Kishore, professor and head, department of community medicine, Safdarjung Hospital.
The rate of infection in the city has also come down with the introduction of RAT. Dr Kishore noted that while it was more than 25 per cent when only RT-PCR tests were conducted, it has come down using RAT as more individuals are being tested for the virus.
“By sero survey, we can get a pulse of what is the infection rate in Delhi. We are moving towards fewer cases by July-end,” Dr Kishore said. As per the government’s order, mild, very mild and pre-symptomatic cases are discharged after 10 days of symptom onset and no fever for three days, without testing.
“In Delhi, majority cases are asymptomatic or mild. If someone is asymptomatic for a long time the possibility of that person becoming severely ill or spreading the infection are very less. So, even if testing is not done, it doesn’t matter. Rather it is better not to waste testing kits in such cases. There might be cases where a patient is positive even after 10 days but that probability is 1 out of 100,” Dr Kishore added.