Article History
Received: 4 January 2019
Accepted: 28 March 2019
First Online: 17 April 2019
Ethics approval and consent to participate
: This study was approved by the Institutional Review Board (IRB approval number: 3–2017-0112) at Gangnam Severance Hospital, Seoul, Republic of Korea. Since data were retrospectively analyzed, consent to participate was not required.
: We did not obtain consent since this study did not contain any individually identifiable data.
: The authors declare that they have no competing interests.
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