Text and Data Mining valid from 2018-04-12
Received: 15 January 2018
Accepted: 4 April 2018
First Online: 12 April 2018
Ethics approval and consent to participate
: This study was approved by the Institutional Review Board of Dongguk University Ilsan Hospital. Individual patient consent was waived because this study did not interfere with patient treatment, and the database was designed so that individual patients could not be identified.
: The authors declare that they have no competing interests.
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