Text and Data Mining valid from 2019-08-22
Received: 23 May 2019
Accepted: 14 August 2019
First Online: 22 August 2019
Ethics approval and consent to participate
: This study had been approved by Ethics Committee of The Third Hospital of Hebei Medical University. There is no need to obtain informed consent from patients because this is a retrospective study and all data were collected and analyzed anonymously.
: Not applicable.
: The authors declare that they have no competing interests.