In COVID-19 Testing, Speed Trumps Sensitivity

With high enough numbers of tested individuals, the exclusive use of rapid antigen tests could achieve similar epidemiological outcomes as using only RT-PCR tests.

AsianScientist (Aug. 10, 2021) – When it comes to minimizing COVID-19 infections, it turns out that the amount of testing may matter more than the sensitivity of tests used. These findings are presented in PLOS Computational Biology.

While vaccinations may be rolling out across the world, the emergence of variants has made it difficult to keep the spread of COVID-19 at bay. As of writing, India has since reported around 32 million cases, with this number largely fuelled by the highly-transmissible Delta variant.

With anecdotes of the Delta variant transmission from just fleeting contact, testing remains paramount in identifying individuals unknowingly infected with COVID-19. In India, two main tests are used to detect SARS-CoV-2: the gold standard reverse-transcriptase polymerase chain reaction (RT-PCR) test and the faster, but less sensitive rapid antigen test.

Though traditional thinking holds that an all-RT-PCR approach will ultimately lead to fewer overall infection, its cost and slow turnaround pose barriers to adoption. Therefore, there is a need to identify the precise mix of tests needed to optimize outcomes while accounting for cost constraints.

To address this question, a team from Ashoka University and the National Centre for Biological Sciences – Tata Institute of Fundamental Research used used computational models to conduct simulations of how COVID-19 spreads among a population, given different combinations of tests and the economic tradeoffs between them.

Accounting for the movement of people between different locations, they calculated the total number of infections that would occur by the end of a pandemic under each scenario.

Their analysis revealed that using only rapid antigen tests could achieve similar epidemiological outcomes as an all-RT-PCR approach in terms of reducing both the peak numbers of infected and the total infected by the end of the epidemic, but only if the number of people tested is high enough.

This suggests that governments in lower and middle-income countries might be able to achieve optimal outcomes by concentrating on ramping up testing using cheaper, less sensitive tests that provide immediate results, rather than favoring RT-PCR.

However, governments should continue to explore different mixes of tests that will yield the biggest reduction in the number of cases. Given that the decreasing costs of testing, this mix could also be recalibrated regularly in light of what makes the most economic sense.

“Tests are continually improving, and the tradeoffs are in favor of rapid testing, even if it is less sensitive,” said study co-author Professor Gautam Menon from Ashoka University. “Modeling the effects of using different combinations of tests, keeping in mind their relative costs, can suggest specific policy changes that will have a substantial effect on changing the trajectory of the epidemic.”

The article can be found at: Cherian et al. (2021) Optimizing Testing for COVID-19 in India.


Source: PLOS; Photo: Shutterstock.
Disclaimer: This article does not necessarily reflect the views of AsianScientist or its staff.

Asian Scientist Magazine is an award-winning science and technology magazine that highlights R&D news stories from Asia to a global audience. The magazine is published by Singapore-headquartered Wildtype Media Group.

Related Stories from Asian Scientist