Footnotes

• FS and YL contributed equally.

• Handling editor Josef S Smolen

• Contributors All authors took part in drafting and revising the article, and all authors approved the final version to be published. XZ and SY had full access to all the data in the study and take responsibility for the integrity and accuracy of the data. Study design: XZ and SY. Acquisition of data: FS, YL, WW and LG. Analysis and interpretation of data: FS, YL and WW.

• Funding The authors have not declared a specific grant for this research from any funding agency in the public, commercial or not-for-profit sectors.

• Competing interests SY has received research funding from the National Key Research and Development Program of China. FS has received research funding from Ren Ji Hospital South Campus, School of Medicine, Shanghai Jiao Tong University. Other coauthors have nothing to disclose.

• Patient consent Not required.

• Ethics approval The ethical approval was waived for this study due to its retrospective design.

• Provenance and peer review Not commissioned; externally peer reviewed.