2.4 Statistics
Statistical analysis was performed using SPSS 19 (IBM Corporation, NY,
USA). The day of onset of symptom was set as day 0. The cumulative
percentages of cases diagnosed by RT-PCR and CT as a function of time
were plotted separately. Following initial positive RT-PCR, the
cumulative percentages on first negative results and final negative
results of follow-up RT-PCR were plotted as well. The CT scores of lung
involvement were plotted over time. The cumulative cases diagnosed by
RT-PCR and CT at different time points were compared by Chi-square test,
two-tailed, and P <·05 was considered statistically significant
difference, as well as for the comparison of chest CT features between
cases with and without coinfection.