Text and Data Mining valid from 2019-03-21
Received: 22 December 2018
Revised: 6 February 2019
Accepted: 27 February 2019
First Online: 21 March 2019
Ethics approval and consent to participate
: This study was approved by the Ethics Committee of Peking Union Medical College Hospital.
: Not applicable.
: The authors declare that they have no competing interests.
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