This is the accepted manuscript version of the work published in its final form as Erjia Ge; Jianhui Gao; Xiaolin Wei; Zhoupeng Ren; Jing Wei; Xin Liu; Xiaomeng Wang; Jieming Zhong; Jingru Lu; Xiaomei Tian; Fangrong Fei; Bin Chen; Xiaolin Wang; Ying Peng; Ming Luo; Juan Lei. BMJ Journals.http://dx.doi.org/10.1136/thoraxjnl-2020-216819 Deposited byshareyourpaper.organdopenaccessbutton.org. We've taken reasonable steps to ensure this content doesn't violate copyright. However, if you think it does you can request a takedown by emailinghelp@openaccessbutton.org.