Funding for this research was provided by:
National Natural Science Foundation of China (81470650, 81670841)
Received: 4 September 2018
Accepted: 29 January 2019
First Online: 6 February 2019
Ethics approval and consent to participate
: The study complied with the principles of the Declaration of Helsinki, and was approved by the National Unit of Clinical trial Ethics Committee, Peking University First Hospital. Written informed consent was obtained from all the parents/legal guardians of the participants.
: Not applicable.
: The authors declare that they have no competing interests.
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