Fig. 1.

Study flowchart.

A total of 690 patients with confirmed COVID-19 between 1 January and 18 March 2020 were included in this study. After excluding patients who had incomplete clinical data, those who were coinfected with other respiratory viruses, and those who were discharged within 24 h after admission, 442 patients were retained in the final analysis. Of these, 333 were hospitalised in Honghu. Simple random sampling in a ratio of 7:3 was performed to assign 231 patients into a training cohort (the Honghu training cohort) and 101 patients into an internal validation cohort (the Honghu internal validation cohort). In addition, 110 patients hospitalised in Nanchang were used as an external validation cohort (the Nanchang external validation cohort).