Received: 12 August 2019
Accepted: 31 October 2019
First Online: 14 November 2019
Ethics approval and consent to participate
: This study was approved by the Conjoint Health Research Ethics Board of Peking University People’s Hospital (No. 2018PHB033–01) and written informed consent forms were obtained from all the participants. The study was carefully conducted complying with the Declaration of Helsinki.
: Not applicable.
: The authors declare that they have no competing interests.