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Article History

Received: 18 November 2017

Accepted: 27 February 2018

First Online: 5 March 2018

Ethics approval and consent to participate

: This study was carried out in accordance with the tenets of the Declaration of Helsinki. It was approved by the Ethics Committee of Peking University Third Hospital. An informed consent was obtained from each subject.

: Not applicable

: The authors declare that they have no competing interests.

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