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Article History

Received: 27 June 2018

Accepted: 12 December 2018

First Online: 3 January 2019

Ethics approval and consent to participate

: The study protocol was approved by the institutional review boards of Medical Center, Seoul National University, Samsung Medical Center, Pusan National University Yangsan Hospital, Seoul National University Bundang Hospital, Hallym University Sacred Heart Hospital, Soonchunhyang University Hospital, Korea University Anam Hospital, Chonbuk National University Hospital, Chungbuk National University, Ulsan University Hospital, Bundang CHA Hospital, Kyung Hee University Hospital at Gangdong, Dongguk University Ilsan Hospital, Gyeongsang National University, and Hallym University Kangnam Sacred Heart Hospital. The need for informed consent was waived due to the retrospective design of the study.

: Not applicable.

: The authors declare that they have no competing interests.

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