Funding for this research was provided by:
Educator Project of Peking Union Medical College (2017zlgc0708)
Received: 15 March 2018
Accepted: 19 July 2019
First Online: 25 July 2019
Ethics approval and consent to participate
: The study was approved by the Ethics Committees of Peking Union Medical College Hospital, and all participants provided written informed consent.
: Not applicable.
: All authors declare that they have no competing interests.