How pool testing can enhance speed, scale
NEWDELHI: The ministry of health and family welfare evaluated this week a testing methodology that could significantly expand its testing capacity, although it is yet to take a final call in the matter.
The methodology is pool or pooled testing, which involves simultaneously testing a combined sample from multiple people from a household or a local cluster to widen reach and speed up results.
Used during large outbreaks and invisible community transmission, such as of HIV, the virus that causes AIDS, this method is now being used to detect shards of the unique genetic material called RNA of Sars-COv2, the virus that causes coronavirus disease (Covid-19). The method uses the highly accurate realtime polymerase chain reaction (RT-PCR) test in a combined sample from several people. If a combined sample comes back positive, each person in the group is isolated and tested separately.
“The more people who can be reliably tested for SARS-CoV-2, the faster the pandemic can be curbed,” said Birgitta Wolff, president of Goethe University, Frankfurt, Germany.
IT INVOLVES TESTING SIMULTANEOUSLY A COMBINED SAMPLE FROM MULTIPLE PEOPLE FROM A HOUSEHOLD OR A LOCAL CLUSTER
IN THE CASE OF A POSITIVE MINI-POOL RESULT, INDIVIDUAL TESTING IS CARRIED OUT OF THE PREVIOUSLY COLLECTED SAMPLES. THE POSITIVE SAMPLE CAN THEN BE IDENTIFIED WITHIN FOUR HOURS
NEWDELHI:The ministry of health and family welfare evaluated this week a testing methodology that could significantly expand its testing capacity, although it is yet to take a final call in the matter.
The methodology is pool or pooled testing, which involves simultaneously testing a combined sample from multiple people from a household or a local cluster to widen reach and speed up results.
Used during large outbreaks and invisible community transmission, such as of HIV, the virus that causes AIDS, this method is now being used to detect shards of the unique genetic material called RNA of Sars-CoV-2, the virus that causes coronavirus disease (Covid-19).
Covid-19 has infected at least 151,000 people and killed 61,000.
The method uses the highly accurate real-time polymerase chain reaction (RT-PCR) test in a combined sample from several people. If a combined sample comes back positive, each person in the group is isolated and tested separately.
Researchers from Israel have demonstrated that testing combined samples from up 64 people for Covid-19 significantly speeded up results, brought down cost and fast-tracked contact tracing, while reducing the workload on labs.
Germany, which has the lowest death rates in Europe, increased testing from 40,000 tests per day to 200,000 to 400,000 tests without compromising accuracy.
“The pool testing has no influence on the detection limit. In the case of a positive mini-pool result, individual testing is carried out in previously reserved samples. The positive sample can then be identified within four hours,” according to researchers from German Red Cross Blood Donor Service in Frankfurt and the Institute for Medical Virology at the University Hospital Frankfurt at Goethe University. “The more people who can be reliably tested for SARS-CoV-2, the faster the pandemic can be curbed,” said Birgitta Wolff president of Goethe University.
India evaluated pooled testing as a method to scale up testing capacity, but did not include the method in its new testing protocol issued on April 4.
“Efforts to increase test capacity by the ‘pooling’ of samples are being evaluated. This is not simple and needs the development and testing of optimization algorithms so that one positive in a large pool is not missed, for example,” India’s principal scientific adviser K VijayRaghavan said on Twitter a week ago.
India has tested just tested 75,000 people for Covid-19, according to the Indian Council of Medical Research, a fraction of its population size of 1.36 billion people.
“India’s testing capacity is a key bottleneck. So far, only around 75,000 people have been tested, with confirmatory results from National Institute of Virology in Pune taking three to four days,” said a public health specialist, requesting anonymity. “It’s a pity because pooled testing detects viral RNA in samples very accurately and helps maximise existing resources. For Covid-19, swab samples from mucous membranes of the nose or throat are combined in a buffer solution, which are then tested using the highly accurate RT-PCR. It can really save costs,” he added.