Text and Data Mining valid from 2019-11-20
Received: 25 September 2019
Accepted: 9 November 2019
First Online: 20 November 2019
Compliance with ethical standards
: The authors declare that they have no conflict of interest.
: The study protocol was approved by the institutional review board of PNUH, Busan, the Republic of Korea (No. 1906-013-080).