Funding for this research was provided by:
Health Industry Research Program Funding Project of Gansu Province (GSWSKY2018- 52)
Article History
Received: 3 December 2019
Accepted: 20 January 2020
First Online: 29 January 2020
Compliance with ethical standards
:
: The authors declare that they have no conflict of interest.
: All procedures performed in the studies involving human participants were in accordance with the ethical standards of the institutional and/or national research committee and with the 1964 Helsinki Declaration and its later amendments or comparable ethical standards. For this type of study formal consent is not required.
: For this type of retrospective study formal consent is not required.