Article History
Received: 11 April 2018
Revised: 30 September 2018
Accepted: 30 November 2018
First Online: 10 January 2019
Compliance with ethical standards
:
: The scientific guarantor of this publication is Jian Gao.
: The authors declare that they have no competing interests.
: Huixin Liu (Department of Clinical Epidemiology, Peking University People’s Hospital, Beijing, China), PhD, provided statistical advice for this study, and she is one of the authors.
: Written informed consent was waived by the Institutional Review Board.
: Institutional Review Board approval was obtained.
: • retrospective• observational• performed at one institution