Pooled Saliva Testing for COVID-19 Can Be Cheaper and as Accurate as Individual Nasopharyngeal Diagnostic Tests

Testing pooled saliva samples twice weekly for SARS-CoV-2 on a residential college campus yielded a greater than 95% agreement with the gold standard for accuracy—nasopharyngeal diagnostic samples tested singly.

The study by researchers at Olivet Nazarene University (Bourbonnais, IL, USA) revealed that at an average of 665 tests per week, the cost, just USD 0.43 per sample, likely remains the least expensive method to date. Using pools of 10 samples, the test provides results in less than eight hours, and is among the most sensitive available, detecting virus at very low viral load, according to the study. This approach enabled successful screening of 43,884 samples, detecting 83% of the semester’s COVID-19 cases. Additionally, the researchers noted that saliva sampling is noninvasive, does not require a transport medium and is stable at room temperature for at least 24 hours.

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In the study, students submitted saliva samples once or twice weekly during spring semester, 2021. Saliva samples were collected every weekday before 9am and delivered to the testing lab. Self-collection by students was handled via the honor system, and fewer than 1% of samples were invalid, with 92% submitted on the assigned date. In the study, 36.2% of those tested were asymptomatic, and 48.3 % of participants reported experiencing “very mild” symptoms at the time of testing. This suggests that without the mandatory testing, 84.5% of students might not have gotten tested on their own at the time of screening. Furthermore, only 56% developed flu-like or severe symptoms during their illness. These results raise the possibility that COVID-19 contagion would have swept the college without the testing program.

“Our study demonstrates a significant step forward for achieving rapid test results on a large scale, while preserving supplies and reducing costs,” said study author Daniel R. Sharda, Ph.D. “Our pooled saliva approach puts routine COVID-19 testing within reach for smaller organizations and countries where resources are limited. Future pandemics should use pooled strategies from the very beginning, when tests are otherwise limited.”

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Olivet Nazarene University