Isolated and remote work settings such as offshore oil drilling platforms face unique challenges in the COVID-19 pandemic. Employees work and live in close contact with one another, quarantining can affect production, and evacuation is expensive.
UF mathematician Burton Singer has been involved with research to help remote work industries learn to navigate the pandemic in ways that protect workers and keep everyone working when it’s safe to do so. Singer is a distinguished visiting professor of epidemiology in the UF College of Liberal Arts & Sciences department of mathematics, and he is also a faculty member in the UF Emerging Pathogens Institute.
In a recent study published in Communications Medicine, a Nature journal, Singer collaborated with a team of researchers from the Yale School of Public Health to assess the performance of 18 commercially available rapid antigen tests against the gold-standard PCR tests when deciding when to end a quarantine. Rapid antigen tests proved to be more useful than given credit for and also proved to be a suitable alternative to gold-standard RT-PCR testing, according to the study’s findings.
Employers often find rapid antigen tests attractive for several reasons, including their low cost, fast turnaround time, widespread availability, and the fact that people can test themselves. But when compared to RT-PCR, rapid antigen tests have a higher rate of false negatives—they are less sensitive to identifying cases with lower viral loads, and a higher rate of false positives—they are less specific at identifying who does not have the disease. This combines to give them a reputation in the public mind as less reliable.
Some companies require a negative test for someone to exit isolation. When a PCR test is used, it’s typically given 24 hours before the anticipated exit. But results can sometimes lag beyond this in areas where testing resources are limited or in times of high viral surges when testing demand swamps the laboratories needed to perform PCR analysis. Further, the results reflect the individual’s infectious state the day prior to, not the day of exit. These limitations are why some employers prefer to use rapid antigen tests. But until now, no studies have been performed to compare the effectiveness of PCR and rapid antigen tests in this context.
Quarantine and infection surveillance focused on SARS-CoV-2 in industrial settings is critical to minimizing or eliminating lost work time of skilled employees whose absence — even in the short term — can lead to significant economic consequences. Offshore oil platforms are an excellent example of this kind of work setting where a single infected individual can rapidly induce local transmission, thereby shutting down production of the platform, resulting in significant economic effects. In work settings like these, rapid and reliable testing is crucial to preserve worker health, safety, and economic productivity.
In the new study, the researchers show that the relative effectiveness of rapid antigen tests and RT-PCR testing in reducing transmission after leaving quarantine depends on the length of the quarantine and the turnaround time of testing results. For quarantines of two days or shorter, conducting a rapid antigen test on exit from quarantine reduces onward transmission more than a single RT-PCR test (with a 24-hour delay) conducted upon exit. And when a complementary approach is used, where testing occurs in serial at a specified frequency paired with isolation of those who test positive, the researchers show that rapid antigen tests outperform RT-PCR when there is a 24-hour delay in obtaining results.
The authors quantified the extent of transmission by developing a mathematical framework informed by COVID-19 infectiousness, test specificity, and temporal diagnostic sensitivity data. Results from the modeling framework were consistent with quarantine and serial testing data collected from a remote industry setting.
By: DeLene Beeland