The United States is testing more than 750,000 people for COVID-19 every day, with demand even higher across states like Arizona, California, Florida and Texas due to a spike in infections. One possible solution is pooled testing in which health officials test small groups — or “pools”– of people for the coronavirus with a single test. If the pooled sample is negative, everyone in the pool is cleared. If the result is positive, each member of the pool is then tested individually. USC experts can explain the potential pros and cons of pooled testing.
As coronavirus spreads, health officials weigh pooled testing
July 30, 2020
Pooled testing could help contain spread and slash costs
“The U.S. doesn’t currently have the capacity to test at a threshold that experts suggest we need to effectively contain the virus. Pooled testing has the potential to get the U.S. one step closer to universal and repeated testing, which is crucial given how quickly we have seen this virus spread. Though the cost savings from pooling decreases in higher prevalence areas, we have shown that even in hot spots where the rate of positive tests is climbing to 10%, pooled testing could reduce costs by around half.
“But the real strength of pooled testing would be seen if health officials start implementing large-scale testing of the general population. The FDA’s recent emergency use authorization to allow Quest Diagnostics to pool samples from up to four patients is an important step in the right direction.”
Erin Trish is associate director of the USC Schaeffer Center for Health Policy & Economics and assistant professor in the Department of Pharmaceutical and Health Economics at the USC School of Pharmacy. She recently co-authored an article on pooled testing for The Conversation along with Darius Lakdawalla, director of research at the USC Schaeffer Center and the Quintiles Chair in Pharmaceutical Development and Regulatory Innovation at the USC School of Pharmacy.
The FDA’s role in protecting public safety
“During this time of global pandemic, the FDA has the challenge of balancing regulatory flexibility with protecting public safety.
“We see the agency expediting access to products with incomplete benefit and/or risk information through the Emergency Use Authorization mechanism, but then pivoting quickly to disallow those demonstrating a lack of efficacy or unacceptable risk profile.”
Eunjoo Pacifici is an expert in drug regulations and the global pharmaceutical market. She is the chair of the Department of Regulatory and Quality Sciences and the associate director of the DK Kim International Center for Regulatory Science at the USC School of Pharmacy.
Pooled testing could help, but costs, challenges await
“Pooling offers the huge advantage of scale and cost effectiveness when the percentage of positive results is small.
“The main disadvantages, as long as the pools are not large enough to affect the accuracy, are mostly logistical. Labs need to be trained to follow the pooling protocol in the case of a positive. Another challenge is trying to convince labs to pool and hence pay a fraction of the cost per person tested.
“Clearly, aggressive testing is the way to get back to normal as soon as possible, with targeted testing in areas of concern and repeated testing for super-spreaders. When testing is used as a defensive screening measure and not as a purely diagnostic tool, pooling is very helpful.”
Kimon Drakopoulos is an assistant professor in the Data Sciences and Operations department at USC Marshall School of Business. His research focuses on the operations of complex networked systems, social networks, stochastic modeling, game theory and information economics.
False negatives are a risk with pooled testing
“The FDA’s decision to authorize pooled sample testing with Quest’s SARS-CoV-2rPT-PCR test, allowing more people to be tested quickly while using fewer testing resources, is at first glance a good decision but one that needs to be taken with caution. Care must be taken not to jump too soon with test kits having lesser sensitivity. The risk of false-negative results for the entire pool can result from using these less-sensitive kits.
“Another potential limitation of pooled testing may result from dilution of positive samples, again resulting in false negatives. Additionally, those people who are asymptomatic or mildly symptomatic will have a lower viral load and, when pooled, may result in false negatives for the entire pool. These two examples give us reason to pause and critically assess our use of pooled testing.”
Susan Bain is an assistant professor in the Department of Regulatory and Quality Sciences at the USC School of Pharmacy. Her expertise is in FDA-regulated industries, incuding the medical device, pharmaceutical and biotechnology industries.