Funding for this research was provided by:
National Research Foundation of Korea (NRF-2017M3C4A7065887)
Ministry of Science and ICT and Ministry of Health and Welfare (C1202-18-1001)
Korean Government Scholarship Program - NIIED, Ministry of Education, South Korea.
Article History
Received: 3 December 2018
Accepted: 2 April 2019
First Online: 25 April 2019
Ethics approval and consent to participate
: This study was approved by the Institution Review Board (IRB)of Korea University, Guro Hospital (with reference number MD14041-002). The board permitted not taking an informed consent due to the retrospective design of this study.
: Not applicable.
: The authors declare that they have no competing interests.
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