Text and Data Mining valid from 2020-03-18
Received: 11 December 2019
Accepted: 6 March 2020
First Online: 18 March 2020
Ethics approval and consent to participate
: The protocol used in this study has been approved by Cangzhou Central Hospital and all patients have read and signed informed consent.
: All authors have given consent for publication.
: The authors declare that they have no competing interests.