Received: 5 June 2019
Accepted: 20 September 2019
First Online: 15 November 2019
Ethics approval and consent to participate
: The only record of contacting subjects for identification and research is the informed consent document, signed informed consent poses an undue threat to the subject’s privacy. This study is based on retrospective analysis, exemption from ethical approval and informed consent will not adversely affect the subject’s rights and health. Therefore, this study is exempt from ethical approval and informed consent.
: Not applicable.
: The authors declare that they have no competing interests.