Received: 23 October 2020
Accepted: 18 January 2021
First Online: 28 January 2021
Ethics approval and consent to participate
: This study was approved by the institutional review board of Hokkaido University Hospital (019–0070) and Japan Community Health Care Organization Hokkaido Hospital (2020-4). The committees did not require informed consent for this retrospective study. We put information of this study on Hokkaido University’s and Japan Community Health Care Organization Hokkaido Hospital’s home page with the opportunity to opt out.
: Not required.
: The authors declare that they have no competing interests.