Materials and Methods
We investigated the viral kinetics of 10 COVID-19 patients diagnosed at Chosun University Hospital, Gwangju, Korea. Of the 10 patients, 6 were classified into the “mild” group and 4 into the “severe” group on the basis of their supplemental oxygen use during admission.
Chest radiograph scores were calculated by using 121 chest radiographs obtained for the 10 patients during admission at their bedside. The scores were obtained by dividing each lung into the upper, middle, and lower zones and scoring each zone from 0 to 4 points on the basis of the degree of infiltration. The scores of each lung were then added considering a total of 6 zones, yielding a total score ranging from 0 to 24 (Conway et al., 1994).
Ribonucleic acid (RNA) was extracted using a nasopharyngeal swab to detect SARS-CoV-2. The sputum specimens were quantified by using the real-time reverse transcription-polymerase chain reaction (RT-PCR) assay, targeting the E and RdRP genes. A SARS-CoV-2 test kit manufactured by Kogene Biotech (Seoul, Korea) was used, with a cut-off cycle threshold (Ct) value of higher than 35 cycles. Moreover, we compared the positive rate of SARS-CoV-2 on the PCR test when the cut-off value was 38 cycles and 35 cycles.
The Ct value of the test results performed on the day of symptom onset and incubation period or asymptomatic phase were included in the results for day 0 since symptom onset. The test results from day 2 to day 4 since the day of symptom onset were included in the results for day 3 since symptom onset. The test results from day 5 to day 7 day since the day of symptom onset were included in the results for day 6 since symptom onset.
Moreover, the Ct values between the severe and mild groups were compared with the Wilcoxon rank sum test by using Stata 14.2 (Stata LLC, TX, USA). P-values less than 0.05 were considered significant.