Text and Data Mining valid from 2019-01-08
First Online: 8 January 2019
Compliance with ethical guidelines
: Y. Huang, X. Liu, X. Xu and J. Liu declare that they have no competing interests.
: All procedures performed in studies involving human participants were in accordance with the ethical standards of the institutional and/or national research committee and with the 1975 Helsinki Declaration and its later amendments or comparable ethical standards. This study was approved by the Ethics Committee of the Jining No. 1 People’s Hospital of Shandong. Informed consent was obtained from all individual participants included in the study.