e-Paper
Fast but less accurate "rapid antigen tests" now account for 60 per cent of all Covid-19 tests in India, the head of a top diagnostic firm estimated on Wednesday, warning that such a high use could misrepresent the actual spread of the infection.
Antigen devices return results in about 15 minutes compared with several hours for the reverse transcription polymerase chain reaction (RT-PCR) method, a laboratory-based process which the United States Centers for Disease Control and Prevention calls the"gold standard" for Covid-19 detection.
Whereas antigen tests typically detect the virus around 80 per cent to 90 per cent of the time, lab-based tests detect the virus more than 95 per cent of the time, say regulators and health experts in countries like the US.
As a consequence of the reduced accuracy, India's high use of antigen tests compared with a global use of around 10 per cent risked underestimating the spread of the coronavirus, according to the founder of Mumbai-based Thyrocare Technologies, one of India's top three diagnostic chains.
"It's a wrong scale used to assess the extent of the spread of the virus," Mr Arokiaswamy Velumani told Reuters.
Though the total number of coronavirus cases reached close to eight million on Wednesday, India's official tally shows daily new cases have dropped sharply since a mid-September peak.
Mr Velumani said Thyrocare's centres are now receiving only about 2,500 samples a day for RT-PCR tests, down from a high of about 7,000 last month.
The health ministry and the Indian Council of Medical Research did not immediately respond to e-mails from Reuters seeking comment on Mr Velumani's comments.
RT-PCR dominates in the US but authorities there are planning to increase the use of antigen tests to screen people.
India's central health ministry has not provided a breakdown of the test methods deployed, but state and federal officials have repeatedly defended the use of antigen tests to quickly identify infections in the country of 1.3 billion people.
It has also helped India quickly ramp up its testing capacity to 1.5 million samples a day.
No state in India has been screening whole communities or populations with either rapid antigen tests or RT-PCR, reported The Hindu.
Instead, the states follow syndromic surveillance where testing is carried out on people who exhibit fever or any other Covid-19 symptoms.
The Indian Council of Medical Research has asked the states to validate all negative results from rapid antigen tests with an RT-PCR.
"There was a stigma that India was not doing enough tests," Mr Velumani said, noting at least that criticism is being addressed.
Reuters
