Funding for this research was provided by:
National Natural Science Foundation of China (81401627)
Medical Development Research Foundation of the Capital of China (2014-4-2025)
Natural Science Foundation of Beijing Municipality (7132087, 7172058)
Beijing Municipal Administration of Hospitals Clinical Medicine Development of Special Funding (ZYLX201702)
Received: 16 July 2017
Accepted: 29 December 2017
First Online: 22 January 2018
Ethics approval and consent to participate
: Not applicable, our study was analyzed retrospectively and it conforms to the provisions of the Declaration of Helsinki.
: Not applicable.
: The authors declare that they have no competing interests.
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