Sensitive detection and quantification of SARS-CoV-2 in saliva

Area of Science:

• Virology and Infectious Diseases
• Molecular Diagnostics
• Public Health

Background:

• Saliva offers advantages for SARS-CoV-2 detection, including ease of collection and safety.
• Validation of saliva-based testing in diverse patient cohorts is crucial for assessing its utility.
• Current diagnostic methods rely heavily on nasal swabs, necessitating exploration of alternative specimen types.

Purpose of the Study:

• To develop and validate a saliva-based testing pipeline for SARS-CoV-2 nucleic acid detection.
• To compare the diagnostic performance of saliva testing against nasal swabs in outpatients and inpatients.
• To evaluate the potential of droplet digital PCR (ddPCR) for quantifying viral loads in saliva.

Main Methods:

• Development of a saliva testing pipeline utilizing real-time reverse transcription PCR (RT-PCR) and ddPCR.
• Collection and testing of saliva samples from 137 outpatients and 29 hospitalized COVID-19 patients.
• Comparison of saliva test results with Emergency Use Authorization (EUA) certified nasal swab results.

Main Results:

• Saliva testing achieved 100% (RT-PCR) and 93.75% (ddPCR) detection rates for SARS-CoV-2 positive curbside patients.
• Viral load quantification by ddPCR revealed a dynamic range of over one million-fold.
• Saliva testing demonstrated comparable reliability to nasal swabs in both community and hospital settings.

Conclusions:

• Saliva testing is a reliable alternative to nasal swabs for SARS-CoV-2 detection.
• The combination of saliva and ddPCR offers enhanced sensitivity for detecting low viral loads.
• Saliva-based diagnostics hold significant potential for widespread SARS-CoV-2 screening and management.