Funding for this research was provided by:
the Scientific Research Foundation for the Returned Overseas Chinese Scholars, State Education Ministry (NO: [2015]311)
Article History
Accepted: 20 February 2018
First Online: 28 February 2018
Compliance with ethical standards
:
: The authors declare that they have no conflict of interest.
: The study was approved by the Ethics Review Board of the School of Medicine, Shandong University (Reference No. LL-201401044), and the research adhered to the tenets of the Declaration of Helsinki.
: Informed consent was obtained from all individual participants included in the study.