Funding for this research was provided by:
Shandong Key Research and Development Plan (2019GSF108219)
Received: 6 June 2019
Accepted: 21 April 2020
First Online: 13 May 2020
Ethics approval and consent to participate
: Written informed consent was obtained from each participant before the sample collection. The study was approved by the ethical committee of Shandong Provincial Hospital and was performed according to the declaration of Helsinki.
: Not applicable.
: The authors declare no conflict of interest. There are no financial and non-financial competing interests (political, personal, religious, ideological, academic, intellectual, commercial or any other) to declare in relation to this manuscript.