Performance of Saliva Samples for COVID-19 Diagnosis by Using the AllplexTM 2019-nCoV Assay Kit

Cecilia V Tapia; Campos Marcia; Mora Ivone; Pozas Nadia; Morales Lesly; Guzmán Camila; Aguilera Valentina; Ibarra Paula; Magne Fabien

doi:10.3389/fmed.2021.617399

Performance of Saliva Samples for COVID-19 Diagnosis by Using the Allplex^TM 2019-nCoV Assay Kit

Front Med (Lausanne). 2021 Feb 24:8:617399. doi: 10.3389/fmed.2021.617399. eCollection 2021.

Authors

Cecilia V Tapia¹, Campos Marcia¹, Mora Ivone¹, Pozas Nadia¹, Morales Lesly¹, Guzmán Camila¹, Aguilera Valentina¹, Ibarra Paula², Magne Fabien³

Affiliations

¹ Laboratorio de Especialidad Clínica Dávila, Santiago, Chile.
² Alatheia Medical Company, Santiago, Chile.
³ Programa de Microbiología y Micología, Facultad de Medicina, Instituto de Ciencias Biomédicas, Universidad de Chile, Santiago, Chile.

Abstract

Background: Although the nasopharyngeal swab (NPS) is the reference sampling method for the detection of SARS-Cov-2, it is not always possible to collect NPS in some patients. Saliva represents an interesting sampling method because it is less invasive and more convenient in patients with nasal or pharyngeal lesions. Objective: To compare the RT-qPCR test performances of saliva samples with nasal mid-turbinate swab (NMTS) and NPS samples in a cohort of ambulatory patients suspected of having COVID-19. Study Design: For each of the 112 enrolled patients, NPS, NMTS, and saliva samples were collected and tested for SARS-Cov-2 detection using three different target genes (RdRP, N and E genes) by RT-qPCR. Results: Among the positive samples (56/112), saliva samples showed a lower percentage of SARS-Cov-2 detection compared to NPS samples, (85.7 vs. 96.4%), while still a lower percentage was observed for NMTS samples (78.6%). In average, saliva samples showed higher Ct values for all tested target genes, compared to those from NPS and NMTS samples. Conclusions: By using the Allplex^TM 2019-nCoV Assay Kit, saliva samples showed lower sensitivity for SARS CoV-2 compared to NPS samples; however, the not detected cases had lower viral burden in NPS samples (CT values >33) representing an interesting alternative sampling method in patients in which it is not possible to take a NPS sample.

Keywords: COVID-19; RT-qPCR; SAR-CoV-2; nasopharangeal swabs; saliva.