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Article History

Received: 19 February 2018

Accepted: 26 June 2018

First Online: 11 July 2018

Ethics approval and consent to participate

: This is a cross-sectional study conducted at the Peking University People’s Hospital (PUPH) from Oct 2015 to Feb 2017 and approved by the PUPH ethics committee (2014PHB098–01). All volunteers were informed and signed the consent form.

: Not applicable

: The authors declare that they have no competing interests.

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