Funding for this research was provided by:
National Natural Science Foundation of China (81371591, 81873905)
Medical Scientific Research Foundation of Guangdong Province (A2016590)
Received: 10 October 2019
Accepted: 9 December 2019
First Online: 10 January 2020
Ethics approval and consent to participate
: The requirement for informed consent was waived due to the retrospective nature of the study.
: All authors consent to the publication of this manuscript.
: The authors declare that they have no competing interests.