Evaluating the use of posterior oropharyngeal saliva in a point-of-care assay for the detection of SARS-CoV-2

Emerg Microbes Infect. 2020 Dec;9(1):1356-1359. doi: 10.1080/22221751.2020.1775133.

Abstract

During the Coronavirus disease 2019 (COVID-19) pandemic, logistic problems associated with specimen collection limited the SARS-CoV-2 testing, especially in the community. In this study, we assessed the use of posterior oropharyngeal saliva as specimens for the detection of SARS-CoV-2 in an automated point-of-care molecular assay. Archived nasopharyngeal swab (NPS) and posterior oropharyngeal saliva specimens of 58 COVID-19 patients were tested with the Xpert® Xpress SARS-CoV-2 assay. SARS-CoV-2 was detected in either NPS or saliva specimens of all patients. Among them, 84.5% (49/58) tested positive in both NPS and saliva, 10.3% (6/58) tested positive in NPS only, and 5.2% (3/58) tested positive in saliva only. No significant difference in the detection rate was observed between NPS and saliva (McNemar's test p = 0.5078). The detection rate was slightly higher for N2 (NPS 94.8% and Saliva 93.1%) than that of the E gene target (Saliva: 89.7% vs 82.8%) on both specimen types. Significantly earlier median Ct value was observed for NPS comparing to that of saliva on both E (26.8 vs 29.7, p = 0.0002) and N2 gene target (29.3 vs 32.3, p = 0.0002). The median Ct value of E gene target was significantly earlier than that of the N2 gene target for both NPS (26.8 vs 29.3, p < 0.0001) and saliva (29.7 vs 32.3, p < 0.0001). In conclusion, posterior oropharyngeal saliva and NPS were found to have similar detection rates in the point-of-care test for SARS-CoV-2 detection. Since posterior oropharyngeal saliva can be collected easily, the use of saliva as an alternative specimen type for SARS-CoV-2 detection is recommended.

Keywords: COVID-19; SARS-CoV-2; nasopharyngeal swab; point-of-care testing; saliva.

MeSH terms

  • Adult
  • Betacoronavirus / isolation & purification*
  • Betacoronavirus / pathogenicity
  • Biological Assay*
  • COVID-19
  • COVID-19 Testing
  • Clinical Laboratory Techniques / instrumentation
  • Clinical Laboratory Techniques / methods*
  • Coronavirus Infections / diagnosis*
  • Coronavirus Infections / epidemiology
  • Coronavirus Infections / virology
  • Female
  • Hong Kong / epidemiology
  • Humans
  • Male
  • Middle Aged
  • Oropharynx / virology
  • Pandemics*
  • Pneumonia, Viral / diagnosis*
  • Pneumonia, Viral / epidemiology
  • Pneumonia, Viral / virology
  • Point-of-Care Systems / standards*
  • SARS-CoV-2
  • Saliva / virology
  • Specimen Handling / methods
  • Viral Envelope Proteins / isolation & purification*
  • Viroporin Proteins

Substances

  • E protein, SARS coronavirus
  • Viral Envelope Proteins
  • Viroporin Proteins

Grants and funding

This study was partly supported by Consultancy Services for Enhancing Laboratory Surveillance of Emerging Infectious Diseases and Research Capability on Antimicrobial Resistance, and the Theme-Based Research Scheme (T11/707/15) of the Research Grants Council, the donations of Richard Yu and Carol Yu, the Shaw Foundation Hong Kong Michael Seak-Kan Tong, May Tam Mak Mei Yin Respiratory Viral Research Foundation Limited, Hui Ming, Hui Hoy, and Chow Sin Lan Charity Fund Limited, Chan Yin Chuen Memorial Charitable Foundation, Marina Man-Wai Lee, the Jessie & George Ho Charitable Foundation, Perfect Shape Medical Limited, and Kai Chong Tong.