Text and Data Mining valid from 2019-04-03
Received: 11 September 2018
Accepted: 26 March 2019
First Online: 3 April 2019
Ethics approval and consent to participate
: All procedures performed involving human participants were in accordance with the ethical standards of Qinhuangdao First Hospital of ethical committee and with the 1964 Helsinki declaration and its later amendments or comparable ethical standards. All subjects provided written informed consent before study initiation.
: Not applicable.
: The authors declare that they have no competing interests.
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