Pool Testing Given All-clear: ICMR

If that test is negative, it means that all the people tested are negative


New Delhi: The country’s top health research body has given its nod to ‘pool testing’ in the country in a bid to rapidly increase the number of people tested for the novel coronavirus infection. 

It is critical to increase the number of tests by laboratories and hence it may help to use pooled samples for screening, the Indian Council of Medical Research (ICMR) said in an advisory posted on its website on Monday. 

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The method involves putting multiple swab samples together and testing them using a single RT-PCR test. If that test is negative, it means that all the people tested are negative. If the test is positive, everyone whose samples were part of the test have to be tested separately to identify positive individuals. 

The decision to go for pool testing has been taken keeping in view the exponential rise in the number of Covid-19 cases in the country, ICMR said. “Positivity rate in cases is still low. Hence, it may help to use the pooled samples for screening,” it said.

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The council has recommended pooling of maximum five samples at a time to avoid the effect of dilution leading to false negatives. Such tests are to be initiated only in areas with low prevalence of Covid-19, it said. Besides speeding up test results, the move also leads to “substantial cost savings when a large proportion of pools tests negative”, the advisory said.

A feasibility study was conducted at ICMR’s Virus Research & Diagnostic Laboratory (VRDL) at King George’s Medical University (KGMU), Lucknow, which revealed that performing real-time PCR for Covid-19 by pooling five samples is feasible when the prevalence rates of infection are low. “All individual samples in a negative pool to be regarded as negative. Deconvoluted testing is recommended if any of the pool is positive,” it said.