Story at a glance
- Officials in Wuhan tested 9 million people for the coronavirus.
- Batch testing, where samples are pooled together, could cut costs and save time.
- It’s only recommended for populations where there are low numbers of cases.
After recent cases of COVID-19 in Wuhan, China, Chinese officials set out to test all 11 million residents in the city. To test for the new coronavirus quickly, the health experts pooled samples together and tested them in batches. This approach, called batch or pooled testing, might be a good way to sift through samples from people who are at low risk of being infected, but it may not be appropriate when there is higher disease prevalence in a population.
In Wuhan, officials collected 9 million samples, and as many as 25 percent of them were tested through batch testing, according to the BBC. They found 300 cases of SARS-CoV-2, all asymptomatic.
In the U.S., we have been behind in testing since the coronavirus pandemic began. Now, as many states are in the first phases of reopening, batch testing could be a way to get a snapshot of the caseload in local areas. But this would only work in regions where the number of cases and the overall prevalence of coronavirus cases are already low.
This is because of how batch testing works. Like it sounds, you are testing a large batch, and if the batch tests positive for SARS-CoV-2, then the lab technicians will need to go back and test each sample individually to determine which are the positive cases. This is no longer efficient if many of the batches will come back positive.
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How you divide out the samples could matter in this case. The number of samples in each batch can be optimized for what the estimated prevalence might be. For example, if there is 5 percent prevalence in the population, you would expect 5 cases for every 100 people. You could divide 100 people into 20 groups of five and then test all the individuals in the groups that came out positive. Batch testing also could cut down the amount of reagents and materials needed to run tests.
Health officials are still determining how they would implement batch testing. The federal Food and Drug Administration (FDA) says that they are “open to a variety of novel testing ideas, such as specimen pooling, and encourages all test developers to reach out to us to discuss appropriate validation approaches,” according to Scientific American. Some experts are looking to use computers or robotics to streamline the process, reports Scientific American.
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If people go back to work and school, they will need to be tested often to monitor the status of coronavirus cases in the population. Batch testing could help achieve an adequate level of surveillance while saving money and resources. One group of experts at the University of Southern California (USC) say that batch testing could lower costs of testing by half or three-quarters, with areas with low prevalence saving even more.
Some states are already using this approach. Nebraska started testing in batches in March, and other university leaders are considering batch testing as a tool to help reopen college campuses in the fall. In Nova Scotia, experts are considering the approach as a way to test all people who enter long-term care homes. In countries that have less access to resources, batch testing may be the only feasible way to test a large number of people.
For up-to-date information about COVID-19, check the websites of the Centers for Disease Control and Prevention and the World Health Organization. For updated global case counts, check this page maintained by Johns Hopkins University.
You can follow Chia-Yi Hou on Twitter.
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