Chennai

According to a Corporation official, the Indian Council of Medical Research has instructed States to conduct the pooled sample testing, following which several districts in Tamil Nadu are set to conduct them.

"Areas with positive cases less than 5 per cent of the population will be identified. Then the civic body would pool several sections of the society in 25 groups. Each group will have five persons. For example, the group for office-goers will have samples from five of them," he added.

Once they are pooled in groups, five persons, one from each of the five groups will be tested. If any group tests positive, more tests will be conducted among the particular section. "This will cut cost and manpower as a large number of unnecessary tests can be avoided. As of now, Chennai has more cases and we are contemplating conducting the pooled sample testing once the cases decline. Now we are testing more than 10,000 samples every day, but only around 1,000 test positive," the official said.

Meanwhile, Corporation Commissioner G Prakash said the number of tests in the city would cross 6 lakh in the next 15 days. "We are conducting 7,000 tests per million population," he said.

The Directorate of Public Health has instructed the authorities of 21 districts, including Erode, Salem, Kanniyakumari, Krishnagiri and Coimbatore where the number of cases are less than 5 per cent of the population, to conduct the pooled sample testing. "The method will help in early detection of COVID-19 cases in the community and also improve turn around time (TAT) of the samples tested," the order said. “Pooled testing will enable surveillance and early detection in settings where current transmission is low, and reduce delays in getting results,” said Dr Prabhdeep Kaur, deputy direction, National Institute of Epidemiology (ICMR), Chennai, and a member of the government’s panel of medical experts.

HOW IT'S DONE

Sample pooling will help increase coronavirus testing capacity, early identification 

• Samples from several individuals are pooled and tested together in a single tube using sensitive molecular biological detection methods
• Individual samples tested only if the pool sample tests positive
• This testing strategy is most efficient in areas with low prevalence, meaning most results are expected to be negative
• Pooling of more than 5 samples is not recommended to avoid the effect of dilution leading to false negatives 
• Pooling of sample is not recommended in areas or population with positivity rates of >5 per cent for COVID-19

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