Text and Data Mining valid from 2018-11-15
Received: 27 February 2017
Accepted: 30 October 2018
First Online: 15 November 2018
Compliance with ethical standards
: The authors declare that they have no conflict of interest.
: The study was approved by the ethics committee of the Peoples’ Hospital of Liaocheng City.
: Due to the retrospective and anonymized design of the study, written consent from the participants was deemed not to be required.