Bean Extract-Based Gargle as Promising Tool for Efficient Diagnosis of COVID-19 at Early Stage Using Rapid Antigen Tests: A Clinical, Prospective, Diagnostic Sensitivity Study

Background: Antigen based rapid diagnostic test (Ag-RDT) is faster and applicable for self-testing of SARS-CoV-2. Nasopharyngeal swab (NPS) is not technically feasible for self-testing due to requirement of heath professional and risk of contaminated aerosol during sample collection. Thus, saliva specimen can be appropriate for self-sampling technique required for Ag-RDT. However, the detection of virus by Ag-RDT in saliva could be less sensitive. Therefore, we aimed to evaluate novel Beanguard gargleTM (BG)-based virus collection method that can be applied to antigen-rapid detection test (Ag-RDT) as an alternative to the current RT-PCR with a nasopharyngeal swab (NPS) for early diagnosis of COVID-19. Methods: Paired BG-based saliva and NPS specimens were collected from 102 patients with COVID-19 and 100 healthy subjects. The diagnostic performance of Ag-RDT (BG-Ag-RDT) and RT-PCR (BG-RT-PCR) of BG-based saliva specimens for SARS-CoV-2 detection was compared to NPS-RT-PCR. Physical interactions between the bean extract (BE) in BG and SARS-CoV-2 were evaluated using cryo-electron microscopy (cryo-EM), isothermal titration calorimetry, and ELISA. Findings: BG-Ag-RDTs showed high sensitivity (97·8%) and specificity (100%) in all patients within 6 days of illness associated with the infection of SARS-CoV-2 along with Alpha and Delta variants. Notably, in 11 asymptomatic early-stage cases, both BG-Ag-RDTs and BG-RT-PCR showed excellent performance with sensitivity and specificity of 100%. The interaction between SARS-CoV-2 spike proteins and truncated canavalin, an active ingredient from BE, was shown by calorimetry. The ultrastructural features of SARS-CoV-2 particles coated by BE were well observed in cryo-EM, and the detachment of the receptor binding domain of SARS-CoV-2 from hACE2 was increased with increasing concentration of BE in ELISA, allowing us to apply for releasing the virus from hACE2 in the oral cavity to early diagnosis. Interpretation: BG-based saliva specimens applied to Ag-RDT can be an alternative to NPS-RT-PCR for early diagnosis of COVID-19. The method can facilitate self-testing without trained healthcare workers for mass screening, surveillance, and efficient quarantine. Funding: BIO3S, Inc., Korea Basic Science Institute, and Jeonbuk National University Hospital. Declaration of Interest: DSK received grant support for clinical study from BIO3S, Inc. DK, JK and BV were involved in developing Beanguard gargleTM. All disclosures are unrelated to present clinical study. All other authors declare no competing interests. Ethical Approval: Ethical approval for the study was granted by the Institutional Review Board of Jeonbuk National University Hospital (CUH 2021-04-036-002) and written informed consent statements were obtained from all participants.