Funding for this research was provided by:
Text and Data Mining valid from 2020-02-05
Received: 5 June 2019
Accepted: 30 January 2020
First Online: 5 February 2020
Ethics approval and consent to participate
: We declare that the study has been performed in accordance with the Declaration of Helsinki and has been approved by the institutional review board of Korea University Ansan Hospital (approval number: 2019AS0051). The requirement for written informed consent was waived by the board.
: Not applicable.
: The authors declare that they have no competing interests.