Received: 16 January 2019
Accepted: 14 February 2020
First Online: 24 February 2020
Ethics approval and consent to participate
: The study protocol was approved by the Institutional Review Board of Huizhou the third people’s Hospital, which absolved the need for written informed consent because of the retrospective study. All personal identification data were anonymized and de-identified before analysis.
: Not applicable.
: The authors declare that they have no competing interests.