May 13, 2020 - As public health experts express concerns about the lack of widespread COVID-19 testing, researchers have proposed a new approach — group screening, according to Scientific American.
If scientists can pool samples from multiple people into groups and evaluate those pools for the coronavirus rather than individuals, fewer tests could be required. This strategy has been used to detect HIV, chlamydia, malaria and influenza and is being considered now by scientists in the U.S., Israel and Germany, the magazine reported.
“As long as we have no vaccine, we can only stop the transmission of the virus by testing and isolation of people who are infected,” Sandra Ciesek, director of the Geothe University Frankfurt’s Institute of Medical Virology in Germany, told the magazine. She was one of the first scientists to report asymptomatic spread of COVID-19 and co-authored a New England Journal of Medicine letter in mid-February about the spread in Germany.
The group technique is described as a “numbers game.” To examine 100 people, scientists could divide samples into five groups of 20 and test each pool. If a pool tests negative, that eliminates one group with the use of one test. If a pool tests positive, the scientist then retests each individual sample in that pool to identify the positive case. This example would use 25 tests rather than 100.
The FDA is now open to this idea, a spokesperson told the magazine, and “encourages all test developers to reach out to us to discuss appropriate validation approaches.”
Other approaches are being developed to eliminate the need to retest pooled samples by creating various combinations of samples that are tested in different pools simultaneously. This takes computer algorithms and robotics to design, the magazine reported.
Group testing has limitations, of course. Diluting samples into pools could create false negatives, and the group approach counts on a large number of samples being negative. If most pools test positive, for instance, that leads to a large number of individual tests, which defeats the purpose.
The prevalence of cases varies widely across U.S. communities, but as the rates flatten and drop, group screening could be useful for factories, hospitals and schools, the magazine reported.