Text and Data Mining valid from 2019-01-03
Accepted: 28 December 2018
First Online: 3 January 2019
Compliance with ethical standards
: The authors have no conflicts of interest or financial relationships relevant to this article to disclose.
: All procedures performed in studies involving human participants were in accordance with the ethical standards of the institutional and/or national research committee and with the 1964 Helsinki declaration and its later amendments or comparable ethical standards. The study was approved by the institutional review board of Severance Hospital (approval number: 4-2017-1101).
: A waiver of informed consent was granted because the study was determined to be minimal risk and because data are de-identified.