Detection of SARS-CoV-2 antigen by rapid antigen test (RAT)
The RT-qPCR-characterized samples were tested with the RAT Standard ™ Q
COVID-19 Ag test (SD Biosensor, Inc., Republic of Korea). The standard ™
Q COVID-19 Ag test is an immunoassay that detects SARS-CoV-2
nucleocapsid protein by lateral flow technique. The test device consists
of a membrane with control and test lines that are pre-coated with mouse
monoclonal anti-SARS-CoV-2 antibody and anti-chicken IgG antibody,
respectively. The mouse monoclonal anti-SARS-CoV-2 antibody conjugated
with color particles are used as detectors for SARS-CoV-2 antigen. A
colored test line would be visible, with various intensity, if
SARS-CoV-2 nucleocapsid protein were present in the specimen. The test
procedure was all done under BSL-2 following the manufacturer’s
instruction. Briefly, the VTM, containing the NP and OP fluids, was
first vortexed for 20 seconds and only 100 μl thereof was placed into
the sample port of the cassette and incubated at room temperature for
15-30 minutes until reading the results in a blinded approach (i.e.
without knowing the RT-qPCR results of the samples).