Despite Maharashtra govt rule, RT-PCR way less than antigen tests

Although the ICMR’s recommended ratio for RT-PCR tests and Rapid Antigen Tests is 70:30, the city’s ratio in June has been 50:50

Even though the state government has insisted on considering only RT-PCR tests’ positivity rate to unlock an area, statistics have revealed that Rapid Antigen Tests (RAT) still form a major chunk of testing in the city. The ICMR has recommended a 70:30 ratio of RT-PCR and RAT, which means out of 100 tests, 70 should be RT-PCR.

But in June, among the average 28,831 tests daily in the city, the ratio for the two tests was 50:50, and in the past week, there were more RATs than RT-PCR tests.

In a recent order, the state government has clearly mentioned that unlocking will be done based on the test positivity rate (TPR) of RT-PCR tests and not RATs.

While RT-PCR is considered the gold standard of Covid-19 tests, RATs give instant results.

A woman gets tested for Covid-19 at Dadar station on June 28. Pic/Ashish Raje

RAT strategy during peak

Despite the 70:30 ratio, the strategy changed during the peak of the second wave when faster results were important. As the wave recedes, the state government is insisting on monitoring Covid-19 based on RT-PCR tests’ TPR.

RATs have a high proportion of negative results even in Covid-19 positive samples. Yet, the city continues to be highly dependent on RATs for mass testing. Especially since June 21, the number of antigen tests has been higher than RT-PCR tests.

“We have increased the overall number of tests with the help of RATs, but now we are trying to maintain a ratio. The TPR of RTPCR tests is around four per cent,” said Suresh Kakani, additional municipal commissioner. The TPR of antigen tests has been around one per cent in the past two weeks.

Testing trends

From June 1 to 26: 7,49,600
Average daily tests: 28,831
Average daily RT-PCR tests: 14,561
Average daily RATs: 14,269
Ratio of RT-PCR to RAT: 50:50
Recommended ratio: 70:30

Antigen vs RT-PCR tests
Date    RATs               RT-PCR
    (thousands)    (thousands)
June 21    19.5              12.8
June 22    20.3              17.6
June 23    19             16.8
June 24    16             14.9
June 25    17.2             16.6
June 26    16.4             16.3

28,831
Average no. of daily Covid-19 tests in Mumbai in June

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