Funding for this research was provided by:
Beijing Municipal Science & Technology Commission (Z181100001718112)
Received: 7 November 2018
Accepted: 31 March 2019
First Online: 27 April 2019
Ethics approval and consent to participate
: The study protocol was approved by the Ethics Committee of Peking University Biomedical Sciences (PKUSSIRB-201733018). The informed consent obtained from all participants was written.
: Not applicable
: The authors declare that they have no competing interests.
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