Received: 15 July 2018
Accepted: 5 June 2019
First Online: 24 June 2019
Ethics approval and consent to participate
: The study protocol was approved by the Institutional Review Board of Chungbuk University Hospital (CBNUH 2015–04–004-002). Informed consent requirements were waived because the study was based on routinely collected administrative data, and patient data were kept anonymous.
: It is not applicable in this section.
: The authors declare that they have no competing interests.