Funding for this research was provided by:
National Research Foundation of Korea (NRF-2016R1C1B2014792)
Text and Data Mining valid from 2018-04-13
Received: 9 January 2018
Accepted: 8 April 2018
First Online: 13 April 2018
Ethics approval and consent to participate
: This study was approved by the Institutional Review Board of Asan Medical Center, and informed consent was waived because of the retrospective nature of the study. The datasets used and/or analysed during the current study are available from the corresponding author on reasonable request.
: The authors declare that they have no competing interests.
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