Footnotes

• Handling editor Mary Frances McMullin.

• Contributors SAM conceived and wrote the manuscript. MFM, SP and QH critically reviewed and edited content. RC and MM critically reviewed content and were involved in national implementation of the Ig policy. MF provided and validated data on Ig use in ITP.

• 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 SAM chairs the Immunoglobulin Policy Working Group at NHS England.

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