Received: 15 June 2017
Accepted: 17 October 2018
First Online: 30 October 2018
Ethics approval and consent to participate
: This study has been conducted according to the principles expressed in the Declaration of Helsinki. Written informed consent was obtained from all participants, and this study was approved by the institutional review board of SMG-SNU Boramae Medical Center.
: Not applicable.
: The authors declare that they have no competing interests.
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