Acknowledgements
Funding statement: This study was supported by the Grant for Key Disciplinary Project of Clinical Medicine under the Guangdong High-level University Development Program (002-18119101). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.

Conflict of interest: None declared.
Authors’ contributions: CL and LJC collected the data, analysed the data and drafted the manuscript. XC, LJC, CPP and HC revised the manuscript. MZ and HC convened the idea and designed the study.