Article History
Received: 15 January 2019
Accepted: 15 March 2019
First Online: 15 April 2019
Compliance with ethical standards
:
: On behalf of all authors, the corresponding author states that there is no conflict of interest.
: This study was approved by the Committee of Ethics in Research of the First Hospital of Qinhuangdao (2016C005).
: All participants provided their written informed consent to participate in this study, after approval of the process by the ethics committee.