Footnotes

• Handling editor Josef S Smolen

• Contributors SZ analysed the data and wrote the manuscript, with significant input from all coauthors. GJM and GTJ are Chief Investigator and Deputy Chief Investigator, respectively, on BSRBR-AS and designed the study and oversaw its conduct. In the current project, they discussed results and provided input into drafts of the manuscript. NJG, KG, DMH and RJM contributed towards design of the current analysis and drafting of the manuscript.

• Funding The BSRBR-AS is funded by the British Society for Rheumatology (BSR) who have received funding for this from Pfizer, AbbVie and UCB.

• Disclaimer Pfizer, AbbVie and UCB receive advance copies of manuscripts for comments. They have no input in determining the topics for analysis or work involved in undertaking it.

• Competing interests None declared.

• Patient consent for publication Not required.

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