Footnotes

• Funding This work was supported by the Prinses Beatrix Fonds (PB 0703) (Prinses Beatrix Fonds and Kersten Foundation, Postbus 85810, 2508 CM Den Haag, The Netherlands) and The Netherlands ALS Foundation (The Netherlands ALS Foundation, Zekeringstraat 42, 1014 BT Amsterdam, The Netherlands). The research leading to these results has received funding from the European Community's Health Seventh Framework Programme (FP7/2007–2013) (259867) (European Commission, DG Research—Unit F06, CDMA 02/069, B-1049 Brussels, Belgium).

• Contributors PTCvD, AG, WvR, JHV, MAvE and LHvdB were all involved in the conception, design and acquisition of data. Analysis was performed by PTCvD, AG and WvR. PTCvD and AG wrote the first draft that was revised and approved by JHV, MAvE and LHvdB.

• Competing interests LHvdB received travel grants and consultancy fees from Baxter, and serves on the advisory board for Biogen, Cytokinetics. JHV received travel grants from Baxter. The other authors report no competing financial interests.

• Patient consent Obtained.

• Ethics approval Medical Research Ethics Committee University Medical Center Utrecht.

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