Received: 10 September 2017
Accepted: 9 May 2018
First Online: 18 May 2018
Ethics approval and consent to participate
: All participants read the purpose statement of the investigation and signed the informed consent. This study has been approved by the Research Ethics Committee in West China Clinical Medicine School and have therefore been performed in accordance with the ethical standards laid down in the 1964 Declaration of Helsinki and its later amendments.
: Consent for publication was obtained in all participants.
: The authors declare that they have no competing interests.
: Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.