Funding for this research was provided by:
National Natural Science Foundation of China (81370816)
Natural Science Foundation of chongqing Science and Technology Commission (cstc2012jjA10136)
chongqing municipal health bureau (2011-1-016)
Article History
Received: 15 February 2019
Accepted: 23 August 2019
First Online: 2 September 2019
Ethics approval and consent to participate
: This study was conducted in accordance with the principles of the Declaration of Helsinki, and the study protocol was approved by the Ethics Committee of The First Affiliated Hospital of Chongqing Medical University (IRB number: 2017-060). We did not obtain written informed consent from all participants, because this was a retrospective observational study.
: Not applicable.
: The authors declare that they have no competing interests.