Comparison of viral load between saliva and nasopharyngeal swabs for SARS-CoV2: the role of days of symptoms onset on diagnosis

Author(s)

Alberto Fernando Oliveira Justo ^[1] ; Mariana Sardinha Bueno ^[2] ; Gabriela Rodrigues Barbosa ^[3] ; Ana Helena Perosa ^[4] ; Joseane MA Carvalho ^[5] ; Nancy Bellei ^[6]

Affiliation

^[1] Universidade Federal de São Paulo. Departamento de Medicina. Laboratório de Virologia Clínica - Brasil

^[2] Universidade Federal de São Paulo. Departamento de Medicina. Laboratório de Virologia Clínica - Brasil

^[3] Universidade Federal de São Paulo. Departamento de Medicina. Laboratório de Virologia Clínica - Brasil

^[4] Hospital São Paulo. Laboratório Central - Brasil

^[5] Universidade Federal de São Paulo. Departamento de Medicina. Laboratório de Virologia Clínica - Brasil

^[6] Universidade Federal de São Paulo. Departamento de Medicina. Laboratório de Virologia Clínica - Brasil

• Document type: Journal article
• Source: Memórias do Instituto Oswaldo Cruz; v. 116, 2021-04-16.

Abstract

BACKGROUND Coronavirus disease 2019 (COVID-19) is highly infectious causing millions of deaths worldwide. Nasopharyngeal swabs are the primary sample of choice for the diagnosis of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), thus, to decrease the exposure to potentially infected samples through the collection is a key point to reduce the risk of infection in healthcare workers. OBJECTIVES This study aimed to evaluate the sensitivity and viral load of saliva specimens by days of symptoms onset comparing to nasopharyngeal swabs in subjects with mild symptoms. METHODS Saliva and nasopharyngeal swabs samples were collected from São Paulo Hospital workers presenting mild symptoms, such as fever, cough, sore throat, rhinorrhea, myalgia, headaches, anosmia, ageusia, and fatigue. To understand the positivity and viral load, reverse transcription-polymerase chain reaction (RT-PCR) was performed. FINDINGS Saliva specimens presented a sensitivity of 98.6% compared to nasopharyngeal swabs. Overall, saliva showed lower viral load compared to nasopharyngeal swabs, regarding days of symptoms onset on diagnosis, the first four days had significant changes in viral load and no significant difference was reported in the days five to nine. MAIN CONCLUSIONS Although RT-PCR of saliva has presented a lower viral load compared to nasopharyngeal swabs, saliva specimens are a potential and reliable candidate for COVID-19 diagnosis through RT-PCR. (AU)

• FAPESP's process: 20/11719-0 - Detection, viral load and phylogenetic analysis of SARS-CoV-2 in samples of volunteers from the vaccine ChAdOx1 nCoV-19 clinical trial
• Grantee: Gabriela Rodrigues Barbosa
• Support Opportunities: Scholarships in Brazil - Doctorate