Article History
Received: 29 March 2018
Accepted: 20 May 2018
First Online: 24 May 2018
Ethics approval and consent to participate
: All participants have given informed and written consent. This study was approved by the ethics committee of Cangzhou Central Hospital, and followed the ethical guidelines laid down in the 1975 Declaration of Helsinki.
: All participants have given consent for publication.
: The authors declare that they have no competing interests.
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