Text and Data Mining valid from 2019-04-13
Received: 28 December 2018
Accepted: 23 March 2019
First Online: 13 April 2019
Compliance with Ethical Standards
: All authors declare that they have no competing interests.
: The study was approved by the ethics committee of Anzhen Hospital. Written informed consent was obtained from the legal guardians.
: 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 1964 Helsinki eclaration and its later amendments or comparable ethical standards.
: Informed consent was obtained from all individual participants included in the study.