Clinical Validation of a Sensitive Test for Saliva Collected in Health Care and Community Settings with Pooling Utility for Severe Acute Respiratory Syndrome Coronavirus 2 Mass Surveillance

The clinical performance of saliva compared with nasopharyngeal swabs (NPSs) has shown conflicting results in health care and community settings. Pooled testing with saliva is also challenging, owing to the ambiguous sensitivity, limit of detection, and processing challenges. A total of 429 matched NPS and saliva sample pairs, collected in either health care or community setting, were evaluated. Phase 1 (protocol U) tested 240 matched NPS and saliva sample pairs; phase 2 (SalivaAll protocol) tested 189 matched NPS and saliva sample pairs, with an additional sample homogenization step before RNA extraction. A total of 85 saliva samples were evaluated with both protocols. In phase 1, 28.3% (68/240) samples tested positive for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) from saliva, NPS, or both. The detection rate was lower in saliva compared with NPS samples (50.0% versus 89.7%). In phase 2, 50.2% (95/189) samples tested positive for SARS-CoV-2 from saliva, NPS, or both. The detection rate was higher in saliva compared with NPS samples (97.8% versus 78.9%). Of the 85 saliva samples evaluated with both protocols, the detection rate was 100% for samples tested with SalivaAll, and 36.7% with protocol U. The limit of detection with SalivaAll protocol was 20 to 60 copies/mL. The pooled testing approach demonstrated a 95% positive and 100% negative percentage agreement. This protocol for saliva samples results in higher sensitivity compared with NPS samples and breaks the barrier to using pooled saliva for SARS-CoV-2 testing.