Article History
Received: 8 April 2019
Accepted: 9 May 2019
First Online: 17 May 2019
Ethics approval and consent to participate
: This retrospective observational study was approved by the Institutional Review Board (IRB) of Seoul National University Bundang Hospital (IRB approval number: B-1806/474–105; approval date: 2018. 6. 11), which waived the requirement to obtain informed consent from the subjects.
: Not applicable.
: The authors declare that they have no competing interests.
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