RSS Avon Local Group, 14 October 2008 A Matching Algorithm for Paired Living Kidney Donation in the UK Joanne Allen – Senior Statistician NHS Blood and Transplant

RSS Avon Local Group, 14 October 2008 Background

RSS Avon Local Group, 14 October 2008 Blood group and tissue type incompatibility prevent many potential living donor kidney transplants A simple exchange of suitable donor kidneys is one possible solution Couple 1 Couple 2 Recipient 1Recipient 2 Donor 1 Donor 2 Paired living kidney donation XX Human Tissue Act made this possible in the UK from Sept 2006

RSS Avon Local Group, 14 October 2008 The British Transplantation Society and NHS Blood and Transplant worked together to develop arrangements for paired donation in the UK – working party Diverse range of views A national scheme –is required by the HTA –will maximise the potential of paired donation - although a local bias is preferred –will be regularly reviewed –should be limited to paired rather than pooled donation initially Background

RSS Avon Local Group, 14 October 2008 Stages involved in the UK paired donation scheme

RSS Avon Local Group, 14 October Say we have 5 couples and couple 1 can swap with any other and couple 4 can swap with couples 3 & 5 Matching process Stage 1: Identify all possible 2-way exchanges Each circle represents one incompatible donor-recipient couple

RSS Avon Local Group, 14 October Matching process Stage 2: Determine all combinations of exchanges

RSS Avon Local Group, 14 October Matching process Stage 2: Determine all combinations of exchanges

RSS Avon Local Group, 14 October Matching process Stage 2: Determine all combinations of exchanges

RSS Avon Local Group, 14 October Matching process Stage 2: Determine all combinations of exchanges

RSS Avon Local Group, 14 October Matching process Stage 2: Determine all combinations of exchanges

RSS Avon Local Group, 14 October X X X X X X X Matching process Stage 3: Optimum combination

RSS Avon Local Group, 14 October X X Matching process Stage 3: Optimum combination

RSS Avon Local Group, 14 October 2008 To determine who is transplanted and who donates to whom Blood group match Local exchange Sensitisation Tissue type match Age difference between the 2 donors Prioritisation factors

RSS Avon Local Group, 14 October 2008 Simulations

RSS Avon Local Group, 14 October 2008 Having identified relevant factors, simulations were written in SAS and were used to inform decision-making on effective waiting list sizes appropriate weights for prioritisation factors likely chance of transplant for different types of patient Simulations based on real data from 20 centres –400 transplants that could not proceed over 2-year period due to blood group and/or tissue type incompatibility Simulations

RSS Avon Local Group, 14 October 2008 The SAS simulation program: selects a stratified random sample, ensuring an even mix of blood group and tissue type incompatible couples Identifies all possible two-way exchanges, ensuring that the donors and recipients are blood group and tissue type compatible in both sides of the exchange Determines the priority score for each of the two-way exchanges, based on weights specific to each simulation Determines all combinations of exchanges (or a subset of combinations when dealing with large pool sizes) Determines the optimum combination of exchanges (highest overall priority score), ensuring that each donor and recipient is not involved in more than one exchange 10 simulations for each scoring system and pool size Simulations

RSS Avon Local Group, 14 October 2008 How many couples are needed? No. of couples on list Maximum % transplanted 10 simulations were run for each pool size, using a stratified random sample

RSS Avon Local Group, 14 October 2008 How many points for –Local exchange (based on 5 areas of the UK) –HLA match (4 levels) –Sensitisation (% of blood group identical donors having antigens which are declared unacceptable for the recipient – pool of 10,000) –Age difference between the 2 donors Blood group match – consider restricting use of O donors Identify combination of transplants with highest sum of point scores for individual transplants Prioritisation factors

RSS Avon Local Group, 14 October 2008 Proposed scheme - results FactorMaximum possible % of transplants* Proposed scheme – % of transplants Local exchange Sensitised patients (65-100%) Level 1-3 HLA mm Donor-donor age diff <= 20 yrs * Based on single factor scoring

RSS Avon Local Group, 14 October 2008 FactorMaximum possible % of transplants* Proposed scheme – % of transplants Local exchange5147 Sensitised patients (65-100%) Level 1-3 HLA mm Donor-donor age diff <= 20 yrs * Based on single factor scoring Proposed scheme - results

RSS Avon Local Group, 14 October 2008 FactorMaximum possible % of transplants* Proposed scheme – % of transplants Local exchange5147 Sensitised patients (65-100%) 3533 Level 1-3 HLA mm Donor-donor age diff <= 20 yrs * Based on single factor scoring Proposed scheme - results

RSS Avon Local Group, 14 October 2008 FactorMaximum possible % of transplants* Proposed scheme – % of transplants Local exchange5147 Sensitised patients (65-100%) 3533 Level 1-3 HLA mm4934 Donor-donor age diff <= 20 yrs * Based on single factor scoring Proposed scheme - results

RSS Avon Local Group, 14 October 2008 FactorMaximum possible % of transplants* Proposed scheme – % of transplants Local exchange5147 Sensitised patients (65-100%) 3533 Level 1-3 HLA mm4934 Donor-donor age diff <= 20 yrs 8278 * Based on single factor scoring Proposed scheme - results

RSS Avon Local Group, 14 October 2008 Points for each possible transplant in a combination - Local exchange: 20 points Sensitised patient: 0-50 points for 0-100% sensitised HLA matched transplant: 0–15 points for levels 4 to 1, respectively Small donor-donor age difference: 3 points if <=20 years Also - restrict use of group O donors to group O recipients only The highest scoring combination is identified The maximum possible number of transplants will be achieved Note – at registration, HLA match and donor age requirements can be specified Agreed national matching scheme

RSS Avon Local Group, 14 October 2008 Who is most likely to find a match? Based on 200 simulations of 30 couples, average transplant rates in the first matching run are - 23% blood group incompatible 34% HLA incompatible Among HLA incompatibles

RSS Avon Local Group, 14 October 2008 Who is most likely to find a match? Blood group incompatibleTissue type incompatible

RSS Avon Local Group, 14 October 2008 Where are we now?

RSS Avon Local Group, 14 October 2008 Matching run summary Run no. Run date No. of pairs (potential recipients) No. of exchanges identified (possible transplants) No. of transplants resulting 1Apr 079 (8)One 2-way (2)2

RSS Avon Local Group, 14 October 2008 Matching run summary Run no. Run date No. of pairs (potential recipients) No. of exchanges identified (possible transplants) No. of transplants resulting 1Apr 079 (8)One 2-way (2)2 2Jul 0726 (25)One 2-way (2)2

RSS Avon Local Group, 14 October 2008 Matching run summary Run no. Run date No. of pairs (potential recipients) No. of exchanges identified (possible transplants) No. of transplants resulting 1Apr 079 (8)One 2-way (2)2 2Jul 0726 (25)One 2-way (2)2 3Oct 0732 (31)None

RSS Avon Local Group, 14 October 2008 Matching run summary Run no. Run date No. of pairs (potential recipients) No. of exchanges identified (possible transplants) No. of transplants resulting 1Apr 079 (8)One 2-way (2)2 2Jul 0726 (25)One 2-way (2)2 3Oct 0732 (31)None 4Jan 0866 (65)Three 2-way (6)2

RSS Avon Local Group, 14 October 2008 Matching run summary Run no. Run date No. of pairs (potential recipients) No. of exchanges identified (possible transplants) No. of transplants resulting 1Apr 079 (8)One 2-way (2)2 2Jul 0726 (25)One 2-way (2)2 3Oct 0732 (31)None 4Jan 0866 (65)Three 2-way (6)2 5Apr 0876 (73)Two 2-way & four 3-way (16)2 3-way exchanges considered in April 2008 run onwards, following agreement from the Kidney Advisory Group

RSS Avon Local Group, 14 October 2008 Pooled donation Donor 1 Recip 1 Donor 2 Recip 2 Donor 3 Recip 3 Donor 4 Recip 4 Donor 5 Recip 5 2-way exchange 3-way exchange

RSS Avon Local Group, 14 October 2008 Matching run summary Run no. Run date No. of pairs (potential recipients) No. of exchanges identified (possible transplants) No. of transplants resulting 1Apr 079 (8)One 2-way (2)2 2Jul 0726 (25)One 2-way (2)2 3Oct 0732 (31)None 4Jan 0866 (65)Three 2-way (6)2 5Apr 0876 (73)Two 2-way & four 3-way (16)2 6Jul 0885 (80)One 2-way (2)2 (planned)

RSS Avon Local Group, 14 October 2008 Matching run summary Run no. Run date No. of pairs (potential recipients) No. of exchanges identified (possible transplants) No. of transplants resulting 1Apr 079 (8)One 2-way (2)2 2Jul 0726 (25)One 2-way (2)2 3Oct 0732 (31)None 4Jan 0866 (65)Three 2-way (6)2 5Apr 0876 (73)Two 2-way & four 3-way (16)2 6Jul 0885 (80)One 2-way (2)2 (planned) 7Oct08123 (115)Six 2-way & three 3-way (21)Not yet known

RSS Avon Local Group, 14 October 2008 Matching run summary Run no. Run date No. of pairs (potential recipients) No. of exchanges identified (possible transplants) No. of transplants resulting 1Apr 079 (8)One 2-way (2)2 2Jul 0726 (25)One 2-way (2)2 3Oct 0732 (31)None 4Jan 0866 (65)Three 2-way (6)*2 5Apr 0876 (73)Two 2-way & four 3-way (16)*2 6Jul 0885 (80)One 2-way (2)2 (planned) 7Oct08123 (115)Six 2-way & three 3-way (21)Not yet known * Transplants did not proceed for various reasons

RSS Avon Local Group, 14 October 2008 Blood group composition of October 2008 list Recipient Blood Group Total OABAB Donor Blood Group O A B AB30104 Total Many more A donors than A, AB recipients

RSS Avon Local Group, 14 October 2008 Degree of sensitisation for patients on October 2008 list Calculated sensitisation (%) No. of patients % of patients Total115100

RSS Avon Local Group, 14 October 2008 Future development Altruistic donor Pooled donor couple - 1 Pooled donor couple - 2 Patient on deceased donor transplant list Domino paired/pooled donation

RSS Avon Local Group, 14 October

RSS Avon Local Group, 14 October 2008 Thank You