This guideline was compiled according to the British Society for Haematology (BSH) process at https:// b-s-h. org. uk/ . The Grading of Recommendations Assessment, Development and Evaluation (GRADE) nomenclature was used to evaluate the levels of evidence and to assess the strength of recommendations. The GRADE criteria can be found at http:// www. grade worki nggro up. org. A literature search was carried out using the terms given in Appendix.