Text and Data Mining valid from 2019-04-15
Received: 29 October 2018
Accepted: 18 February 2019
First Online: 15 April 2019
Compliance with ethical standards
: The authors declares that they have no conflict of interest.
: All procedures performed in studies were in accordance with the ethical standards of the Ethics Committee at Peking Union Medical College Hospital and with the 1964 Helsinki Declaration and its later amendments or comparable ethical standards. For this type of study, formal consent is not required.