Funding for this research was provided by:
scientific research fund of hebei provincial health commission (20210120)
333 talents project of hebei province (A202101060)
Received: 18 May 2021
Accepted: 23 July 2021
First Online: 12 August 2021
: The study was approved by the ethical committee of The Third Hospital of Hebei Medical University (W2021-011–1), and all methods were carried out in accordance with relevant guidelines and regulations/Declaration of Helsinki. Informed consent obtained from their parents or legal guardian.
: Not applicable.
: All authors declare no potential conflict of interest.