Review of Liver Distribution and Allocation Scheme
The Hepatitis C Trust, together with other liver patient support charities and liver disease charities have been meeting up with NHS Blood and Transplant (NHSBT) to discuss proposals for a new liver distribution and allocation scheme.
There are several reasons for a new scheme being considered. In the current system in the UK, donated livers are distributed to seven liver transplant centres, with the number of donated livers allocated based on the percentage share of new adult patients on the transplant list at each centre. Any liver retrieved in a particular allocation zone can automatically be used in a patient chosen by the centre in that zone. Most centres give priority to their patients on the basis of a measure of disease severity, with the sickest going first. (This is for those cases which are not ‘super-urgent’ - emergency patients are placed on a national transplant list and are given donated livers from the whole of the UK). In spite of similar selection criteria being used by each of these liver transplant centres, the current liver allocation scheme results in disparities between centres, for example:
- there are significant differences in waiting time to transplantation between the seven liver transplant centres in the UK
- there are differences between the centres in the mortality of patients waiting for a transplant.
- there are differences in survival between the centres over two years from point of registration onto the liver transplant list
Furthermore, in the current centre-based system, when a liver becomes available in that centre’s zone it is offered to a patient in that particular centre even if there is another patient in a different centre with a greater, more urgent need, and who might die as a consequence of not receiving that liver.
There are additional, related concerns about lack of transparency, with the NHSBT stating that ‘the current allocation scheme is not […] understandable by the public on whom support for organ donation resides, and it is difficult to demonstrate that the allocation scheme in one centre is similar or based on the same principles to that in another. A centre-based scheme has difficulty in demonstrating equity of access to all potential recipients.’ 1
A national system of allocation may be a way of addressing the above issues, with all available livers going on a national, rather than regionally-based, list. However, this would mean that there would no longer be input from regional specialists who may have better knowledge of patient need.
As well as considering a changeover to a national system, the NHSBT has been exploring different models of how livers could be allocated to patients on the transplant waiting list. They have carried out statistical modelling on three different schemes in an attempt to assess their relative merits. The proposed schemes are described by the NHSBT1 as:
This ‘prioritises patients according to their survival on the transplant list whilst waiting for a transplant; the patient with the shortest estimated survival time gets offered a liver first. This scheme aims to reduce mortality on the transplant list, but as a consequence may worsen outcome after transplantation (because the patients prioritised are so sick). It takes no account of the quality of the donated liver on offer but simply recommends that the next available liver is offered first to the ‘sickest’ patient.’
This ‘prioritises patients according to their survival after transplantation; the patient with the longest estimated survival time with a particular liver is offered the organ first. This scheme aims to maximise the survival rate after transplantation but may do this at the expense of allowing more to die waiting for a transplant, because the patients with the best outcome after a transplant tend to be the ones with a lower risk of dying without a transplant.’
This ‘prioritises patients by ranking them by the number of additional years of life they gain from a transplant. This is the difference between their estimated survival with and without a transplant. This scheme takes into considered the quality of the donor organ alongside patient characteristics in order to identify the patient who has the greatest number of life-years to gain by a transplant.’
In summary, the findings of the statistical simulation were that all the proposed schemes were better than the current centre based scheme. If allocation were decided on the basis of either the needs-based model, or the benefit model described above, there was a decrease in overall numbers dying, and an increase in the life-years of transplant candidates. It was also found that there was an increase in life-years of transplant candidates with a national list, compared to regional or local lists.
There are many complex variables involved in the statistical simulation, and in the proposals overall. All the information cited in this brief summary has been taken from a report provided by the NHSBT Liver Transplantation: Organ Allocation in the United Kingdom: A report for Liver Disease Charities and Patient Support Groups, January 2012 which can be accessed in full hereThe Hepatitis C Trust is meeting up with the other liver patient support and disease charities on 27 February 2012 to discuss the review again. Two representatives from that group will then feedback to a separate committee, which includes clinicians, and which meets in March. To further complicate the picture, it should be noted that it may ultimately be decided not to change from the current system, and also there is the option of combining elements of any of the current or proposed models!
We would welcome your views and opinions on this complex and potentially controversial and sensitive issue. Let us know what you think – before our meeting on 27 February by emailing Susan.Mcrae@hepctrust.org.uk
National Health Service Blood and Transplant refs. AG: LTAS PSGs jan 12v1 Liver Transplantation: Organ Allocation in the United Kingdom: A report for Liver Disease Charities and Patient Support Groups, January 2012
