Received: 19 November 2018
Accepted: 20 February 2019
First Online: 26 February 2019
Ethics approval and consent to participate
: This study observed the Declaration of Helsinki and current ethical codes and was approved by the ethics committee at the University of Occupational and Environmental Health. This research is not a clinical study, and the data was anonymized for retrospective analyses. Therefore, no written informed consent were obtained from the patients.
: Not applicable.
: The authors declare that they have no competing interests.
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