Funding for this research was provided by:
National Natural Science Foundation of China (81704656)
Key research and development project of Shandong province, China (2018GSF118153)
Article History
Received: 16 October 2018
Accepted: 26 November 2018
First Online: 9 December 2018
Compliance with ethical standards
:
: The authors declare no conflicts of interest.
: All procedures followed were in accordance with the ethical standards of the responsible committee on human experimentation (institutional and national) and with the Helsinki Declaration of 1964 and later versions. This study was approved by local institutional review board from the two hospitals and informed consent was waived according to the retrospective design.