Evaluation of Specimen Types and Saliva Stabilization Solutions for SARS-CoV-2 Testing

Area of Science:

• Virology
• Infectious Diseases
• Diagnostic Testing

Background:

• Accurate SARS-CoV-2 detection is vital for pandemic control.
• Nasopharyngeal swabs (NPS), the gold standard for COVID-19 testing, face supply chain challenges.
• Alternative specimen types like nasal swabs (NS) and saliva are being explored for easier collection and reduced exposure.

Purpose of the Study:

• To compare the diagnostic sensitivity of nasal swabs (NS) and saliva against nasopharyngeal swabs (NPS) for SARS-CoV-2 detection.
• To evaluate the combined detection sensitivity of nasal swabs and saliva.
• To assess the stability of SARS-CoV-2 virus in saliva.

Main Methods:

• Matched nasopharyngeal swabs, nasal swabs, and saliva specimens were collected from two outpatient cohorts (n=463).
• SARS-CoV-2 detection was performed using RT-PCR.
• Spiking experiments and virus stability assays at different temperatures were conducted.

Main Results:

• SARS-CoV-2 detection sensitivity was 97.9% for NPS, 87.1% for NS, and 87.1% for saliva in the second cohort (41% positivity).
• Combining nasal swabs and saliva achieved 94.6% detection sensitivity.
• SARS-CoV-2 remained stable in saliva for up to 7 days at 4°C and room temperature; stabilizing solutions did not improve stability.

Conclusions:

• While NS and saliva show reduced sensitivity compared to NPS, their combination improves detection rates.
• Saliva is a stable specimen for SARS-CoV-2 testing without the need for special transport solutions.
• Further assessment is needed to determine the clinical acceptability of reduced sensitivity for NS and saliva in specific settings.