This is the pre-peer reviewed version of the following article: (2019), Supplement Article. Br J Haematol, 185: 3-202. doi:10.1111/bjh.15854, which has been published in final form at https://doi.org/10.1111/bjh.15854. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Use of Self-Archived Versions.