Text and Data Mining valid from 2018-09-04
Received: 19 June 2018
Accepted: 11 August 2018
First Online: 4 September 2018
Compliance with ethical standards
: The authors declare that they have no conflict of interest.
: This study was conducted in compliance with ethical principles based on the 1964 Declaration of Helsinki and with the approval of the ethics committee of Shandong Provincial Hospital Shandong University.
: Informed consent was obtained from all individual participants included in this study.