Text and Data Mining valid from 2020-03-20
Received: 24 October 2019
Accepted: 28 February 2020
First Online: 20 March 2020
Ethics approval and consent to participate
: All participants were provided with written informed consent at the time of recruitment. And this study was approved by the Ethics Committee of the Second Hospital of Shanodng University.
: The authors declare that they have no competing interests.