Funding for this research was provided by:
Pediatric Clinical Research Center Foundation of Sichuan Province (2017-46-4)
Received: 15 May 2020
Accepted: 21 January 2021
First Online: 30 January 2021
Ethics approval and consent to participate
: The study protocol was approved by the Ethical Committee of West China Second University Hospital and the Medical Ethical Committees of the participating hospitals. Because of the retrospective design of this research, informed consent was waived.
: Not applicable.
: The authors declare that they have no competing interests.