Frontiers in Medicine (Feb 2021)

Prospective Comparison of Saliva and Nasopharyngeal Swab Sampling for Mass Screening for COVID-19

  • Mathieu Nacher,
  • Mathieu Nacher,
  • Mayka Mergeay-Fabre,
  • Denis Blanchet,
  • Orelie Benoit,
  • Tristan Pozl,
  • Pauline Mesphoule,
  • Vincent Sainte-Rose,
  • Véronique Vialette,
  • Bruno Toulet,
  • Aurélie Moua,
  • Mona Saout,
  • Stéphane Simon,
  • Manon Guidarelli,
  • Muriel Galindo,
  • Barbara Biche,
  • William Faurous,
  • Laurie Chaizemartin,
  • Aniza Fahrasmane,
  • Devi Rochemont,
  • Nicolas Vignier,
  • Astrid Vabret,
  • Magalie Demar,
  • Magalie Demar

DOI
https://doi.org/10.3389/fmed.2021.621160
Journal volume & issue
Vol. 8

Abstract

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Current testing for COVID-19 relies on reverse-transcriptase polymerase chain reaction from a nasopharyngeal swab specimen. Saliva samples have advantages regarding ease and painlessness of collection, which does not require trained staff and may allow self-sampling. We enrolled 776 persons at various field-testing sites and collected nasopharyngeal and pooled saliva samples. One hundred sixty two had a positive COVID-19 RT-PCR, 61% were mildly symptomatic and 39% asymptomatic. The sensitivity of RT-PCR on saliva samples vs. nasopharygeal swabs varied depending on the patient groups considered or on Ct thresholds. There were 10 (6.2%) patients with a positive saliva sample and a negative nasopharyngeal swab, all of whom had Ct values <25 for three genes. For symptomatic patients for whom the interval between symptoms onset and sampling was <10 days sensitivity was 77% but when excluding persons with isolated N gene positivity (54/162), sensitivity was 90%. In asymptomatic patients, the sensitivity was only 24%. When we looked at patients with Cts <30, sensitivity was 83 or 88.9% when considering two genes. The relatively good performance for patients with low Cts suggests that Saliva testing could be a useful and acceptable tool to identify infectious persons in mass screening contexts, a strategically important task for contact tracing and isolation in the community.

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