Received: 2 February 2020
Accepted: 25 May 2020
First Online: 11 June 2020
Ethics approval and consent to participate
: The study protocol was approved by the Institutional Review Board of the Ethics Committee of the Affiliated Hospital of Qingdao University with waiver of participant consent (protocol number: QYFY WZLL 25725).
: Not applicable.
: The authors declare that they have no competing interests.