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Article History

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.