ABSTRACT
Omicron is the current variant of
SARS-CoV-2. It has high transmissibility and evades human immunity.
Early and accurate diagnosis is essential for therapy, prognosis, and
curbing the spread of the virus. Here we reported a new sampling method
for the rapid antigen test, with specimens from phlegm, instead of from
nasal swabs. Sensitivities in detection of SARS-CoV-2 antigen were
compared within the two specimens, and between rapid antigen tests with
phlegm specimens and PCR tests. Of 41 volunteers, thirty-one with
positive phlegm specimens of SARS-CoV-2 eventually had typical COVID-19
symptoms, which suggested rapid antigen tests with phlegm specimens had
100 % accuracy. Fourteen of these had antigen tests with nasal swab
specimens: 13 negative and 1 positive. Combined with that the antigen
levels of the 6561-fold diluted phlegm specimen were comparable to those
of the original nasal swab specimen, antigen tests with phlegm specimens
are more sensitive and earlier detect SARS-CoV-2 than with nasal swab
specimens. Interestingly, case studies indicated antigen tests with
phlegm specimens earlier notified patients of positive infection than
PCR tests. Phlegm specimens enhanced sensitivity in detection of
SARS-CoV-2 in antigen tests, resulting in earlier diagnosis (12 to 42
hours, n=6) than nasal swab specimens. The sensitivity of antigen tests
with phlegm specimens is comparable to that of PCR tests, but the former
earlier outputs test results. Rapid antigen tests with phlegm specimens
facilitate monitoring the health of COVID-19 patients and direct
recovery.