Text and Data Mining valid from 2019-01-12
Received: 11 June 2018
Accepted: 10 December 2018
First Online: 12 January 2019
Compliance with ethical standards
: All authors declare that there is no conflict of interest.
: This study was approved by the Ethics Committee of The Affiliated Hospital of Qingdao University.
: The written informed consent was obtained from all the patients.