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

Area of Science:

• Virology
• Infectious Diseases
• Molecular Diagnostics

Background:

• Saliva offers advantages for SARS-CoV-2 detection, including ease of collection and safety.
• Validation in large patient cohorts is crucial for assessing saliva testing's potential and limitations.
• Current diagnostic methods rely on nasal swabs, necessitating exploration of alternative specimen types.

Approach:

• Developed a saliva testing pipeline for SARS-CoV-2 nucleic acid detection using real-time reverse transcription PCR (RT-PCR) and droplet digital PCR (ddPCR).
• Compared saliva test results with nasal swab results from 137 outpatients and 29 inpatients.
• Utilized Emergency Use Authorization (EUA) certified nasal swab assays for comparison.

Key Points:

• Saliva testing demonstrated high sensitivity, detecting 100% (RT-PCR) and 93.75% (ddPCR) of SARS-CoV-2 positive cases identified by nasal swabs.
• Droplet digital PCR (ddPCR) revealed a wide dynamic range in viral loads, spanning up to one million-fold differences.
• Saliva testing proved reliable in both community screening and hospital settings, matching nasal swab accuracy.

Conclusions:

• Saliva testing is a viable and accurate alternative to nasal swabs for SARS-CoV-2 detection.
• The combination of saliva testing with ddPCR offers potential for enhanced sensitivity in detecting low viral loads.
• Further validation supports the widespread adoption of saliva-based diagnostics for infectious diseases.