PCR and Rapid Diagnostic Test on Saliva and Nasopharyngeal Swabs for the Detection of SARS-CoV-2 (COVID-19)

Background: Recent literature shows that the sensitivity of the PCR tests for the detection of SARS-CoV-2 using saliva samples is close to that using nasopharyngeal swabs. This type of sampling represents a practical advantage since it can be performed by the patient herself/himself and would thus allow to speed up the collection process. It is also less painful and could prevent the rare lesions to the nasal mucosa that can occur when using nasopharyngeal swabs. Rapid Diagnostic Tests for the detection of SARS-CoV-2 antigens have been developed using nasophayngeal swabs and have shown very high sensitivity against PCR, ranging from 93% to 98% when based on laboratory validation, 80% when based on clinical validation.This method offers the considerable advantage to inform the patient of the test result on site, and allow the provision of appropriate recommendations on the spot of testing. The studies performed so far have been conducted using nasopharyngeal samples only. There are no data with saliva yet. It is expected that the RDT would also work on the saliva. Even if slightly less sensitive due to the fact that it detects antigens and not multiplied RNA as PCR does, RDT on saliva could better serve the public health goal to test widely and quickly and have ultimately more COVID cases detected and isolated, and hence reduced transmission. To investigate the case detection rates of both PCR on saliva and nasopharynx and RDT on nasopharynx and saliva, patients will be taken four samples, two swabs on saliva, one for RDT and one for PCR, and two swabs on nasopharynx, one for RDT and one for PCR. Patients who have at least one of the common symptoms and who consent to such a procedure will be recruited to compare the four results. The primary objective is to compare the case detection rates for SARS-CoV-2 of the four testing methods (two sampling types and two test types). Methods: Procedures: Patients fulfilling inclusion and exclusion criteria will be recruited consecutively. After confirmation of inclusion and exclusion criteria, patients will be asked whether they would be willing to provide two saliva samples and one nasopharyngeal swab in addition to that provided for routine testing. After written informed consent, patients will be asked to perform swabbing of the gingiva-buccal fold two times and a saliva sample under professional supervision, once for sending to the laboratory to perform PCR, and once for performing the RDT onsite according to manufacturer's information. They will also be taken two nasopharyngeal swabs, one for RDT and one for PCR. No coughing or sniffing prior to sample collection is required. Ideally, water should be avoided 10 minutes prior to collection. Other drinks, food, and nasal sprays should be avoided 20 minutes before sample collection. The saliva and nasopharyngeal samples will be analysed by PCR according to the standard procedure. The RDTs will be performed and results read according to the manufacturer information (see below). Alternatively one of the three following tests will be tested: RDT from Roche (Standard Q COVID-19, the RDT from Abbott (Panbio COVID-19 Ag) and the RDT from AAZ-LMB (COVID-VIRO). The patient will be considered as positive for SARS-CoV-2 if any of the test results (by RDT, or PCR on saliva or nasopharynx) is positive.