Received: 26 November 2017
Accepted: 21 March 2018
First Online: 2 April 2018
Ethics approval and consent to participate
: The study protocol conformed to the Declaration of Helsinki and was approved by the Ethics Committee of the First Affiliated Hospital of Xi’an Jiaotong University. All the participants provided written informed consent.
: Not applicable.
: The authors declare that they have no competing interests.
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