Article History
Received: 24 November 2018
Accepted: 12 February 2019
First Online: 23 February 2019
Compliance with ethical standards
:
: The authors declare that they have no conflict of interest.
: This study was approved by the Ethics Committee of Beijing Friendship Hospital, Capital Medical University.
: All procedures performed in studies involving human participants were in accordance with the ethical standards of the institutional and/or national research committee and with the 1964 Helsinki declaration and its later amendments or comparable ethical standards.
: Informed consent was obtained from all individual participants included in the study.