Comparison of COVID-19 Antigen Rapid Test (Oral Fluid) and Real-Time RT-PCR in the laboratory diagnosis of SARS-CoV-2 infection

Severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) was first diagnosed in December 2019. Since then this virus has caused an ongoing wide pandemic. Accurate diagnostic tests for SARS-CoV-2 are used to prevent the virus from spreading. However, these tests could not keep up with the demand and were not available in all places. Self-testing devices are easy-to-use-tests and reduce the demand in the diagnostic laboratories. The Antigen Rapid Test evaluated in this study uses oral fluid which is a non-invasive technique compared to nasopharyngeal swabs. In this study the COVID-19 Antigen Rapid Test (Oral fluid) was evaluated with 150 SARS-CoV-2 positive saliva specimens and 350 SARS-CoV-2 negative saliva specimens. The Antigen Rapid Test was performed according to the instruction manual. SARS-CoV-2 Real-time RT-PCR was used as Golden Standard. Although the criteria of the WHO are specific to nasal / nasopharyngeal samples (and not saliva), the specificity of the Antigen Rapid Test meets the criteria of the World Health Organization (WHO; specificity ≥ 97%). The test meets the WHO sensitivity criteria in samples with higher viral loads (Ct<30), showing the better performance of the test in highly positive samples. For positive SARS-CoV-2 specimens with a Ct value lower than 30 a sensitivity of 83.8% (95% CI: 80.1%-86.8%) and an accuracy of 95.9% (95% CI: 93.7%-97.4%) was observed. This shows that this assay with saliva samples is able to meet the high standards set by the WHO. The performance of the test is comparable to other antigen rapid tests reported in meta-analyses. Furthermore, the test allows self-testing which is non-invasive, affordable and straightforward. This antigen rapid test may provide an affordable, quick, and easy to perform method to differentiate between individuals with high and low viral loads. ### Competing Interest Statement This study was commissioned by Healthmark (Rotterdam, the Netherlands) and Healthmark provided the Alltest COVID-19 Antigen Rapid Test (Oral fluid) for this study. ### Funding Statement This study was commissioned by Healthmark (Rotterdam, the Netherlands). ### Author Declarations I confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained. Yes The details of the IRB/oversight body that provided approval or exemption for the research described are given below: Anonymised rest materials may be used for research according to the law for medical treatment (WGBO: Wet op de geneeskundige behandelingsovereenkomst). All samples used in the study are anonymous spare human materials, and none of the participants objected to the use of the material for future research purposes. The usage of the samples has been reviewed by the medical ethics review committee of the Maastricht University Medical Centre and ethical oversight was waived. I confirm that all necessary patient/participant consent has been obtained and the appropriate institutional forms have been archived, and that any patient/participant/sample identifiers included were not known to anyone (e.g., hospital staff, patients or participants themselves) outside the research group so cannot be used to identify individuals. Yes I understand that all clinical trials and any other prospective interventional studies must be registered with an ICMJE-approved registry, such as ClinicalTrials.gov. I confirm that any such study reported in the manuscript has been registered and the trial registration ID is provided (note: if posting a prospective study registered retrospectively, please provide a statement in the trial ID field explaining why the study was not registered in advance). Yes I have followed all appropriate research reporting guidelines and uploaded the relevant EQUATOR Network research reporting checklist(s) and other pertinent material as supplementary files, if applicable. Yes All data produced in the present study are available upon reasonable request to the authors