These Guidelines are guides to best practice which inevitably change with time. All practitioners need to undertake clinical care on an individual basis and keep themselves up to date with changes in practice of clinical medicine. The joint NHS Blood and Transplant and British Transplantation Society Guidelines ("the Guidelines") were compiled by a working party of NHSBT and the BTS. The Guidelines represent the collective opinions of a number of experts in the field and do not have the force of law. The Guidelines contain information and guidance for use by practitioners as a best practice tool; it follows that the Guidelines should be interpreted as such rather than the letter of their contents. The opinions presented in the Guidelines are subject to change and should not be considered to be a treatment recommendation for any individual patient.