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Kidney Offering Scheme

During 2015, three working groups were established to consider whether any improvements could be made to the 2006 UK Kidney Allocation Scheme.

This review was in response to the increased use of donors after circulatory death (DCD) and generally older, more challenging donor kidneys.

The three groups were tasked with:

  • reviewing the current scheme
  • looking at the philosophy of allocation
  • looking at histocompatibility and immunogenetics


The working groups agreed that a new Kidney Offering Scheme should be introduced to better match patient and graft life expectancy and to give more priority to difficult to match patients.

Key terms

Histocompatibility is the compatibility between the tissues of different individuals, so that one accepts a graft from the other without giving an immune reaction.

Immunogenetics is the branch of medical genetics that explores the relationship between the immune system and genetics.

Materials and methods

In line with agreed objectives, a series of computer simulations were used to explore a number of different offering scheme algorithms.

The simulations were developed using:

  • 4,100 UK deceased kidney donors that resulted in a transplant between 2013 and 2016
  • 5,300 patients listed in the UK for a kidney only transplant at 1 January 2012
  • 8,200 patients newly listed for a kidney only transplant between 2012 and 2016


Each simulation represented four years of constant activity.

Simulation results of different possible schemes were compared according to characteristics of the simulated transplant and waiting list pools in order to find the best compromise between competing objectives.

The simulations included use of donor and recipient risk indices developed with the working groups.

Key objectives:

  • unify the donation after brain death (DBD) and DCD offering with all DBD and DCD kidneys allocated through scheme
  • more effective ‘quality’ matching between donor and recipient
  • better tailored human leukocyte antigen (HLA) matching by age
  • geographical equity of access
  • avoid prolonged waiting times that are predictable
  • waiting time from earliest of start of dialysis or activation on the list
  • age should be a continuous factor

Comparing the two schemes

2006 Kidney Allocation Scheme

All DBD donors are allocated by national rules:

  • Tier A - paediatric patients - 000: HSP or HLA-DR homozygous
  • Tier B - paediatric patients - other 000
  • Tier C - adult patients - 000: HSP or HLA-DR homozygous
  • Tier D - adult patients - other 000 + and paediatric patients (100, 010, 110)
  • Tier E - all other patients


Prioritisation

Within tiers patients are prioritised by a points score including:

  • waiting time
  • tissue match and age combined
  • age difference
  • location
  • blood group match

Proposed Offering Scheme

All deceased donors are allocated by national rules: 

  • Tier A - patients with matchability score=10, 100% cRF or ≥7 years waiting time
  • Tier B - all other patients


Prioritisation

Tier A - patients are prioritised by matchability and waiting time

Tier B - patients are prioritised by a points score including:

  • donor-recipient risk index combinations
  • waiting time from earliest of dialysis or activation on the list
  • tissue match and age combined
  • location
  • match-ability
  • total mismatch
  • blood group match

Key terms

Matchability is a measure of how it difficult it is to match a patient with an organ donor in the UK.

This score takes into account a patient’s blood type, HLA type and unacceptable antigens.

A patient with a score = 1 is defined as easy to match and a score = 10 as difficult to match.

Conclusion

A new UK Kidney Offering Scheme launched in September 2019.

It was developed to reflect the changing donor pool and to address some of the inequities observed in the 2006 scheme.

The new scheme allocates all kidneys from both DBD and DCD donors and more effectively matches graft life expectancy with patient life expectancy.