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Article History

Received: 2 May 2018

Accepted: 13 February 2019

First Online: 18 February 2019

Ethics approval and consent to participate

: The Dalian Medical University Ethics Committee approved the study without informed consent, as the samples were remnants following clinical use and therefore not specifically collected for this study and without risk to patients.

: Not applicable.

: The authors declare that they have no competing interests.

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