Mouth Washing Impaired SARS-CoV-2 Detection in Saliva

Monique Melo Costa; Nicolas Benoit; Hervé Tissot-Dupont; Matthieu Million; Bruno Pradines; Samuel Granjeaud; Lionel Almeras

doi:10.3390/diagnostics11081509

Mouth Washing Impaired SARS-CoV-2 Detection in Saliva

Diagnostics (Basel). 2021 Aug 22;11(8):1509. doi: 10.3390/diagnostics11081509.

Authors

Monique Melo Costa^{1

2

3}, Nicolas Benoit^{1

2

3

4}, Hervé Tissot-Dupont^{3

5}, Matthieu Million^{3

5}, Bruno Pradines^{1

2

3

4}, Samuel Granjeaud⁶, Lionel Almeras^{1

2

3}

Affiliations

¹ Unité de Parasitologie et Entomologie, Département de Microbiologie et Maladies Infectieuses, Institut de Recherche Biomédicale des Armées, 13005 Marseille, France.
² Aix Marseille Univ, IRD, SSA, AP-HM, VITROME, 13005 Marseille, France.
³ IHU Méditerranée Infection, 13005 Marseille, France.
⁴ Centre National de Référence du Paludisme, 13005 Marseille, France.
⁵ Aix-Marseille-Université, IRD, MEPHI, IHU Méditerranée Infection, 13005 Marseille, France.
⁶ CRCM Integrative Bioinformatics Platform, Centre de Recherche en Cancérologie de Marseille, INSERM, U1068, Institut Paoli-Calmettes, CNRS, UMR7258, Aix-Marseille Université UM 105, 13009 Marseille, France.

Abstract

Background: A previous study demonstrated the performance of the Salivette^® (SARSTEDT, Numbrecht, Germany) as a homogeneous saliva collection system to diagnose COVID-19 by RT-qPCR, notably for symptomatic and asymptomatic patients. However, for convalescent patients, the corroboration of molecular detection of SARS-CoV-2 in paired nasopharyngeal swabs (NPS) and saliva samples was unsatisfactory.

Objectives: The aim of the present work was to assess the concordance level of SARS-CoV-2 detection between paired sampling of NPSs and saliva collected with Salivette^® at two time points, with ten days of interval.

Results: A total of 319 paired samples from 145 outpatients (OP) and 51 healthcare workers (HW) were collected. Unfortunately, at day ten, 73 individuals were lost to follow-up, explaining some kinetic missing data. Due to significant waiting rates at hospitals, most of the patients ate and/or drank while waiting for their turn. Consequently, mouth washing was systematically proposed prior to saliva collection. None of the HW were diagnosed as SARS-CoV-2 positive using NPS or saliva specimens at both time points (n = 95) by RT-qPCR. The virus was detected in 56.3% (n = 126/224) of the NPS samples from OP, but solely 26.8% (n = 60/224) of the paired saliva specimens. The detection of the internal cellular control, the human RNase P, in more than 98% of the saliva samples, underlined that the low sensitivity of saliva specimens (45.2%) for SARS-CoV-2 detection was not attributed to an improper saliva sample storing or RNA extraction.

Conclusions: This work revealed that mouth washing decreased viral load of buccal cavity conducting to impairment of SARS-CoV-2 detection. Viral loads in saliva neo-produced appeared insufficient for molecular detection of SARS-CoV-2. At the time when saliva tests could be a rapid, simple and non-invasive strategy to assess large scale schoolchildren in France, the determination of the performance of saliva collection becomes imperative to standardize procedures.

Keywords: COVID-19 diagnosis; SARS-CoV-2; coronavirus; saliva.

Abstract

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