medicine & health
Covid-19 Testing Reaches New Heights with Pooled Testing Procedures
Image by HFCM Communicate. [CC-BY-SA 4.0]
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By Shanelle Jayawickreme
ave you been tested for Covid-19? As I anxiously awaited to take my test, deep down I wondered if I was being exposed to the virus at that very minute, standing in a long line. Sitting in my chair, part of me knew only a thin layer of disinfectant spray served as the barrier between my germs and those of the people who preceded me. Luckily, I ended up testing negative. This is not the case for the group of people who test positive, or the even larger population affected by limited access to resources and funding for testing and treatment sites in their area. The COVID-19 outbreak has dominated the lives of U.S. citizens well into 2020, leaving many struggling to find stability in a period of overwhelming uncertainty. Although the coronavirus pandemic has been present for over seven months, the public constantly Dr. Daniel Westreich craves more information on how to better handle this situation. With increasing demand and a limited supply of testing resources, it is imperative that new solutions and strategies are publicized for the greater good. UNC-Chapel Hill researchers Daniel Westreich and Michael G. Hudgens from the department of Epidemiology and the department of Biostatistics, respectively, in collaboration with Christopher D. Pilcher from the University of California San Francisco, have proposed a solution for upscaling COVID testing. “Pooled testing of a virus is an efficient way to move the testing agenda forward,” allowing for higher productivity and proper utilization of resources when compared to individual testing methods already in place.1 Pooled testing is a procedure that has been used for many decades by scientists and involves combining individ-
ual swab samples into one big pool before testing for the virus. In the case that the test comes back negative, the scientists save a large quantity of testing materials by only using one set for the entire cohort. If instead the pooled sample yields a positive result, then each individual sample within the pool is retested in order to identify those responsible for the positive result. This process can also involve an intermediary stage, in which the total group assay is split into smaller and smaller groups until the positive tests are located. In this manner, testing resources are conserved while still allowing the scientists to observe the results of each sample.
Figure 1. Pooled Testing Procedures. Image courtesy of Jean-Etienne Minh-Duy Poirrier [CC BY-SA 2.0]
Westreich began by producing a model that illustrated the distribution of the window for SARS-CoV-2 detection, which predicts changes in viral concentration from the first day to the last day of infection. This proved difficult to consolidate into a mean projection due to the fluctuating nature of the virus.2 Westreich explains, “there is a gap between when you’re infected with the virus, and when your body starts to produce measurable responses to the virus.”1 In that gap, one can be very infectious to others. Vi-
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