Funding for this research was provided by:
Qingdao science and technology project (20-4-1-5-nsh)
Received: 18 March 2020
Accepted: 8 June 2020
First Online: 9 July 2020
Ethics approval and consent to participate
: Study approval and ethical clearance was obtained from the affiliated hospital of Qingdao university. Written consent was obtained from the guardian of the child prior to data collection.
: We obtained the written consent for publication from the guardian of the patient.
: All authors declare that they do not have any conflict of interest.