Received: 30 October 2019
Accepted: 6 May 2020
First Online: 29 May 2020
Ethical approval and consent to participate
: This study was approved by the Ethics Committee of the Medical College, Shantou University. The need for informed consent had been waived due to the retrospective nature of the study.
: Not applicable. The results of this study are just part of our ongoing project. We will consider sharing our data when we finish our project.
: The authors declare that they have no competing interests.