Funding for this research was provided by:
National Research Foundation of Korea (2017R1E1A1A03070961)
Text and Data Mining valid from 2019-06-21
Received: 9 January 2019
Revised: 24 April 2019
Accepted: 29 May 2019
First Online: 21 June 2019
Compliance with ethical standards
: The scientific guarantor of this publication is Kyoung Won Kim.
: The authors of this manuscript declare no relationships with any companies, whose products or services may be related to the subject matter of the article.
: One of the authors (Sang Hyun Choi) has significant statistical expertise.
: The requirement for informed consent was waived due to the retrospective nature of this study.
: This study was approved by our Institutional Review Board.
: • Retrospective• Observational• Performed at one institution