Statistical analysis
Continuous data with a normal distribution were presented as mean ±
standard deviation. If continuous data showed a skewed distribution,
they were presented as a median [interquartile range (IQR)].
Frequency data are expressed as proportions. Comparisons of continuous
variables were made using Student’s t test
or the Mann-Whitney U test when
appropriate, while differences in categorical variables were assessed
using the X2 test or Fisher’s exact test, as
appropriate.
Survival
curves were plotted using the Kaplan-Meier method using a log-rank test.
Multivariate logistic regression models were used to determine the
independent risk factors for severe disease progression to critical
illness during 28 days inpatient observation. Data were analyzed using
SPSS 25.0. A two-tailed P value < 0.05 was considered
statistically significant.