Challenges in use of saliva for detection of SARS CoV-2 RNA in symptomatic outpatients

J Clin Virol. 2020 Sep;130:104567. doi: 10.1016/j.jcv.2020.104567. Epub 2020 Jul 31.

Abstract

Background: A major expansion in SARS CoV-2 testing is urgently needed. Saliva is an attractive option as an alternative for nasopharyngeal swabs (NPS), since saliva can be self-collected, is non-invasive, and sample quality is not dependent on the expertise of the collector.

Objective: To compare SARS CoV-2 positivity on paired NPS and saliva samples.

Study design: NPS and paired saliva samples were prospectively collected from symptomatic outpatients suspected of having COVID-19 and were tested by real-time RT-PCR.

Results: In total, 35/124 (26.6 %) samples were RT-PCR positive, with 33/35 positive by NPS (sensitivity = 94.3 % (95 % CI 81.4%-99.0%)) and 30/35 by pure saliva (sensitivity = 85.7 % (95 % CI 70.6%-93.7%)), for an overall agreement of 117/124 (94.4 %). The median cycle threshold value was significantly lower for NPS than for saliva (p = 0.0331). A third or more of pure saliva samples from symptomatic patients were thick, stringy, and difficult to pipet.

Conclusions: Real-time RT-PCR of pure saliva had an overall sensitivity for SARS CoV-2 RNA detection of 85.7 % when compared to simultaneously collected NPS. Our study highlighted the need to optimize collection and processing before saliva can be used for high volume testing.

Keywords: COVID-19; Nasopharyngeal swab; Real-time RT-PCR; SARS CoV-2; Saliva.

Publication types

  • Comparative Study

MeSH terms

  • Betacoronavirus
  • COVID-19
  • COVID-19 Testing
  • COVID-19 Vaccines
  • Clinical Laboratory Techniques
  • Coronavirus Infections / diagnosis*
  • Humans
  • Molecular Diagnostic Techniques / standards*
  • Nasopharynx / virology
  • Outpatients
  • Pandemics
  • Pneumonia, Viral / diagnosis*
  • Prospective Studies
  • RNA, Viral / analysis*
  • Real-Time Polymerase Chain Reaction
  • SARS-CoV-2
  • Saliva / virology*
  • Specimen Handling

Substances

  • COVID-19 Vaccines
  • Covid-19 aAPC vaccine
  • RNA, Viral