The focus of this research was to determine whether saliva-based testing for COVID-19 was sensitive enough to detect COVID-19 in the community setting, where patients are likely less symptomatic and thus where viral loads are likely lower. We focused on two specific use cases that are critical to loosening social distancing guidelines: Diagnosing new COVID-19 infections in the community setting; and determining if someone is no longer infectious after contracting COVID-19 and thus safe to come into contact with uninfected individuals, such as in a “back to work” scenario.

We enrolled and consented a total of 88 individuals who presented and qualified for testing in the Diagnostic Cohort to evaluate whether self-collected saliva could alleviate some of these challenges. NPS and saliva samples were collected simultaneously from each individual and sent to the Nevada State Health Lab, which used the CDC RT-qPCR assay for diagnostic testing. Saliva samples were sent to Helix, where RNA was extracted and evaluated using the PrimerDesign COVID-19 assay performed at Helix and the TaqPath Multiplex RT-PCR COVID-19 assay performed at UC San Diego.

We found that, relative  to nasopharyngeal swabs, the sensitivity of saliva was approximately 30% lower in a community-based diagnostic cohort and 50% lower in a convalescent cohort. Unfortunately, this suggests that saliva is not sufficiently sensitive to be the broad-based testing modality, even though it may work for acute / admitted COVID patients in the hospital. We will keep working on scalable alternative approaches.