Received: 19 October 2018
Accepted: 15 April 2019
First Online: 15 May 2019
Ethics approval and consent to participate
: All subjects were provided with written informed consent. The study protocol was approved by the Committee on Medical Ethics of the Peking University. The number of ethics approval is IRB00001052–17107.
: Not applicable.
: The authors declare that they have no competing interests.
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