Received: 15 January 2021
Accepted: 3 June 2021
First Online: 29 June 2021
: This study was approved by the National Health Insurance Service of Korea and the Seoul National University Hospital Institutional Review Board (IRB No. E-1907-053-1046). The Institutional Review Board of the Seoul National University Hospital approved the study protocol, and informed consent was exempted by the committee (IRB number: E-1907-053-1046). Informed consent from each patient was waived considering that the NHIS-NSC contains anonymized data. All methods were carried out in accordance with relevant guidelines and regulations.
: Not Applicable.
: The authors declare that they have no competing interests.