FIGURE LEGENDS
Figure 1. Rapid antigen test with phlegm specimens is
more sensitive than that with nasal swab specimens. (A) A patient with
mild symptoms of COVID-19 volunteered simultaneously for rapid antigen
tests with both phlegm and nasal swab specimens. Viral antigens of
phlegm liquids from the deep throat or specimens from the nostril were
extracted with antigen extraction buffer from a rapid antigen test kit.
Three drops of extracted antigen were applied for tests. Test time 0 h
indicated when the phlegm specimen was initially positive, and 12 h was
the passed time after the phlegm specimen was positive; (B) The
phlegm sample was consecutively diluted at 3-fold for a test of
sensitivity in detection of SARS-CoV-2. Sixty microliters of the
original or diluted sample were applied for rapid antigen tests.
SARS-CoV-2 antigen was still detectable in the 2187-fold diluted phlegm.
The antigen levels in the 6561-fold diluted phlegm sample are comparable
to that in the nasal swab sample indicated in rapid SARS-CoV-2 antigen
tests. Control is the antigen extraction buffer only.
Figure 2. The time to detect SARS-CoV-2 in antigen
tests with phlegm specimens is earlier than with nasal swab specimens.
(A) In patient 1, the SARS-CoV-2 antigen in the phlegm specimen was not
detectable on Day 0 and was detected on the next day (Day 1, 0 h).
SARS-CoV-2 antigen in the nasal swab specimen was not detectable at the
beginning of Day 1 (0 h), but detected 13 hours after the phlegm
specimen was positive on the same day (13 h); (B) In patient 2,
on Day 1, SARS-CoV-2 antigen was detected in phlegm specimens (0 h and
13 h). In nasal swab specimens, antigen was not detected (0 h, 13 h)
till Day 2 (24 h) and the relative intensity of the “T” band was
stronger after 35 hours (35 h); (C) In patient 3, SARS-CoV-2
antigen was detected in the phlegm specimen on Day 1 (0 h), but not
detected in nasal swab specimens until 42 hours later on Day 3 (42 h).
The yellow triangle indicates the time when the SARS-CoV-2 antigen was
initially detected in the phlegm specimen; The blue triangle stands for
the time point when the antigen was initially detected in the nasal swab
specimen.
Figure 3. The rapid antigen test with phlegm specimens
notified the patient of SARS-CoV-2 infection earlier than the PCR test.A patient was exposed to a positive case of COVID-19 and collected
specimens for viral detection. On Day 0 , a phlegm specimen was
collected for a rapid antigen test, and the nucleic acid specimen was
collected for a PCR test (the result was notified on Day 1). Both tests
showed negative results. On Day 1 , both phlegm and nasal swab
(N. Swab) specimens were tested for rapid SARS-CoV-2 antigen as
indicated. Viral antigens in the phlegm specimen were detected (0 h),
and a nucleic acid specimen was collected for a PCR test, with
notification of the positive nucleic acid specimen 11 hours after the
phlegm sample was positive (11 h). On Day 2, SARS-CoV-2 antigens from
the nasal swab specimen were detected, 35.5 hours after positive phlegm
was determined (35.5 h). The yellow or blue triangle indicates the time
when SARS-CoV-2 antigens were detected in phlegm or nasal swab specimen
respectively. The green or red triangle designates the time when the
results of a PCR test of SARS-CoV-2 RNA were notified.
Figure 4. Rapid antigen test with phlegm specimen
facilitates monitoring the health of COVID-19 patients. On Day
1 , a tiny amount of SARS-CoV-2 antigen was detected at a weak band in
phlegm (0 h), and the nucleic acid specimen was collected for PCR test
on the same day. On Day 2 , the patient was notified of the
positive nucleic acid sample 10 hours later than
the first positive phlegm
specimen, and the specimen of the nasal swab in antigen test was
detected 21 hours after the first positive phlegm specimen (21 h). The
patient had no symptoms until the nasal swab specimen was positive 21
hours after the first positive phlegm specimen. The patient had a slight
cough, and an increase in body temperature 29 hours post the first
positive phlegm specimen. The yellow, blue, or red triangle indicates
the time when SARS-CoV-2 was initially detected in the phlegm specimen,
the nasal swab specimen, or the nucleic acid sample by a PCR test (time
with the notified result) respectively.
Figure 5. Rapid antigen tests with phlegm specimens can be used
to direct recovery. Day 9 - 12 is the 9th –
12th day after the first positive phlegm specimen.(A) On Days 9 – 11, the nasal swab specimens of Patient 1 were
negative but the phlegm specimens were still positive, indicating a
rapid antigen test with phlegm specimens more accurately showed the
patient’s infection condition. On Day 12, both specimens were negative;(B) On Day 9, both the phlegm and the nucleic acid samples of
Patient 2 were still positive, but the nasal swab specimen by an antigen
test was negative. On Day 10, both the PCR test and the phlegm antigen
test showed negative results. The red or green triangle designates the
time when SARS-CoV-2 nucleic acid specimens were collected and tested as
positive or negative in PCR tests; (C) On Day 11, the phlegm
specimen of Patient 3 was positive but the nasal swab one was negative.
On Day 12 both antigen specimens and the nucleic acid sample with PCR
test became negative in SARS-CoV-2 detection, suggesting the rapid
antigen test with phlegm was comparable to the PCR test directing
recovery from COVID-19.