Funding for this research was provided by:
National Natural Science Foundation of China (81470052)
Text and Data Mining valid from 2020-03-13
Received: 7 December 2019
Accepted: 28 February 2020
First Online: 13 March 2020
Ethics approval and consent to participate
: This study was approved by the ethics committees of the two medical centers. The requirement for obtaining informed consent from patients was waived because the data sets were anonymous.
: Not applicable.
: The authors declare that they have no competing interests.