Funding for this research was provided by:
Capital Health Development Research and Special Projects (2014-2-7051)
High-level Technical Personnel Training Program for Beijing Healthcare System (2014-3-105, 2014-3-106)
Received: 21 September 2017
Accepted: 8 October 2018
First Online: 29 October 2018
Ethics approval and consent to participate
: Not applicable.This study was a retrospective analysis of de-identified data, which did not involve collection, use, or transmittal of individually identifiable data; ethics committee approval was not required.
: Not applicable.
: The authors declare that they have no competing interests.
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