RT-PCR tests in Delhi over past 3 weeks reveal 28% positivity

A swab sample being collected for COVID-19 testing in Delhi on Wednesday.   | Photo Credit: SHIVKUMARPUSHPAKAR

Around 28 out of every 100 people tested through the RT-PCR method were found to be COVID-19 positive, according to Delhi government data (between November 1-24) shared with The Hindu.

The positivity (percentage of people testing positive for every 100 tests done) of 4.11 lakh RT-PCR tests done in this period is around 28.6%.

But the highest overall positivity of Delhi for this period was less than 14%, as it also included results of Rapid Antigen Tests (RAT).

Compared to the past, more RT-PCR tests were done in the city in November following multiple orders from the High Court.

The higher positivity of RT-PCR means that it is one of the reasons for the increase in the number of COVID-19 cases in November.

The city witnessed the highest spike in cases this month, since the outbreak of the pandemic.

From November 1-24, 8.2 lakh tests were done using RAT, and the overall positivity being lesser than RT-PCR, shows that positivity of RAT was comparatively very low.

RT-PCR and RAT are the two main types of tests done to detect COVID-19.

RT-PCR test gives more accurate results compared to RAT. But the former’s result usually comes the next day, while RAT takes only 30 minutes to give a result.

Question over accuracy

In September, the High Court had asked the Delhi government to increase the number of RT-PCR tests and pointed out that the accuracy of RAT was low. Since then, the government has increased RT-PCR testing, but it is still less than the number of RAT done on a daily basis.

The High Court raised the issue in an order on November 11, also. “The number of tests undertaken by the Delhi government from 19.10.2020 till date, reveals that testing through RAT is still being relied upon heavily vis-a-vis testing through RT-PCR and other similar modes. Taking a random example of the testing conducted by the Delhi government during this period would show that figures of testing through RAT has always and invariably been double the testing done through RT-PCR and similar modes, which is not understood when the situation is as critical as it is now and several asymptomatic persons are turning out to be COVID positive.”

“RT-PCR has more specificity and sensitivity compared to RAT. But people being tested using RT-PCR are the ones who have more probability to have the virus and this is also one reason why the positivity is more for RT-PCR,” said Jugal Kishore, head of community medicine department at Safdarjung Hospital. He added that the government should strengthen testing facilities so that RT-PCR testing can be done even in smaller diagnostic centres.

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Printable version | Jan 28, 2021 5:33:42 AM |

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