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 [&ge;] 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.