Diagnostic accuracy of a novel SARS CoV-2 rapid antigen test and usefulness of specimens collected from the anterior nasal cavity

Objectives: We aimed to validate a newly developed antigen-detecting rapid diagnostic test (Ag-RDT) for SARS-CoV-2 using anterior nasal specimens.

Methods: Between February 12 and September 30, 2021, 16 patients (age range, <1 month-76 years) were enrolled, and samples were collected simultaneously from anterior nasal and nasopharyngeal sites continuously during hospitalization. The primary end points were the diagnostic accuracy of the Ag-RDT and utility of anterior nasal specimens.

Results: In total, 226 sets of paired samples were obtained. In 88.2% of specimens, the viral load was high at the nasopharyngeal site. The mean cycle threshold values for the anterior nasal and nasopharyngeal sites were 32.4 and 29.9, respectively. Using the real-time polymerase chain reaction results as a reference, the Ag-RDT showed a 100% sensitivity up to day 6 of the illness, using specimens with moderate or high viral load (cycle threshold <30) from either site. From day 7, the sensitivity was 70.4-90.6% and 83.9-84.6% for the anterior nasal and nasopharyngeal sites, respectively. The specificity remained at 100%.

Conclusion: Our novel Ag-RDT meets the World Health Organization criteria and provides stable sensitivity and specificity and accurate results with anterior nasal specimens.