Text and Data Mining valid from 2018-04-20
Received: 23 December 2017
Accepted: 13 April 2018
First Online: 20 April 2018
Compliance with ethical standards
: The authors declare no conflict of interest.
: This study was approved by the Institutional Review Board of Asan Medical Center (2015-0594) and conducted in accordance with the principles outlined in the Declaration of Helsinki.
: Informed consent was provided by all participants.