Received: 26 October 2019
Revised: 29 May 2020
Accepted: 1 July 2020
First Online: 13 July 2020
Ethics approval and consent to participate
: This study was approved by the Research and Ethical Committee of the Second Hospital of Hebei Medical University, China, basing on the 1964 Helsinki Declaration and its later amendments.
: Not applicable.
: The authors declare that they have no competing interests.