Footnotes

• Handling editor Josef S Smolen

• Twitter @MikeEhrenstein

• Contributors MG and MRE were involved in the design of the study and data interpretation and wrote the manuscript. MG performed the research and collected and analysed the data. MS, S-AY, ER and DM collected, verified and analysed the validation cohort. All authors reviewed and approved the manuscript’s content before submission.

• Funding MG (and MRE in part) are supported by the University College London Hospital Biomedical Research Centre (BRC420).

• Competing interests None declared.

• Patient and public involvement Patients and/or the public were not involved in the design, conduct, reporting or dissemination plans of this research.

• Patient consent for publication Not required.

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