Received: 16 November 2017
Accepted: 14 February 2018
First Online: 20 February 2018
Ethics approval and consent to participate
: This study was approved by the Institutional Review Board of Severance hospital (IRB No.4–2017-0436) and was conducted in accordance with the Declaration of Helsinki. Consent to participate from the patients was waived by the Institutional Review Board of Severance hospital (IRB No.4–2017-0436) as this was a retrospective chart review study.
: Not applicable.
: The authors declare that they have no competing interests.
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