Baseline correction and statistical analysis
The propensity score matching (PSM) method was used to screen symptomatic patients based on the clinical profiles of asymptomatic and presymptomatic COVID-19 patients upon admission to hospital (16). Confounding factors include age, gender, hypertension, diabetes, cardiovascular disease, cerebrovascular disease, cancer, chronic obstructive pulmonary disease, chronic kidney disease, chronic liver disease, and immunodeficiency. For continuous variables, the median and interquartile range (IQR) were used to show the distribution, and the Wilcoxon rank-sum test with two-sided was used to compare the differences between groups. Number and percentage were used to show discrete variables, and Fisher’s exact test with two-sided was used to compare the differences. All statistical analyses were performed using R software.