Text and Data Mining valid from 2018-04-05
Received: 5 December 2017
Accepted: 23 March 2018
First Online: 5 April 2018
Ethics approval and consent to participate
: This study was approved by the Institutional Review Board of the affiliated hospital of Qingdao University. Written informed consent was obtained from all patients enrolled in the investigation.
: Not applicable.
: The authors declare that they have no competing interests.
: Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.