Article History
Received: 19 October 2020
Accepted: 3 February 2021
First Online: 15 February 2021
Ethics approval and consent to participate
: This retrospective cohort study was approved by the Ethics Committee of the second hospital of Hebei Medical University (number 2020-R126), and the need for written informed consent was waived.
: Not applicable.
: The authors declare no competing interests.