Footnotes

• Handling editor Josef S Smolen

• Contributors NvH, AAdB, AvdM, WK, FHJvdH, RFvV, NdB and HWJB were involved in the study design. NvH, AAdB, AvdM and FHJvdH were involved in the data collection. NdB and WK performed the data analyses. All authors were involved in writing, revision and final approval of the manuscript. NdB is the study guarantor.

• Competing interests RFvV: grants from AbbVie, Amgen, BMS, GSK, Pfizer, Roche and UCB, and personal fees from AbbVie, Biotest, BMS, Celgene, Crescendo, GSK, Janssen, Lilly, Merck, Novartis, Pfizer, Roche, UCB and Vertex, outside the submitted work. HWJB: grants and personal fees from Pfizer and AbbVie, during the conduct of the study, and grants and personal fees from Roche, Bristol-Myers Squibb and Union Chimique Belge, outside the submitted work. AAdB: Congress invitations from Roche and AbbVie and an expert witness fee from Amgen.

• Patient consent Not required.

• Ethics approval CMO Regio Arnhem-Nijmegen: NL37704.091.11.

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

• Data sharing statement The authors commit to making the relevant anonymised patient-level data available on reasonable request.