Seven Non-Simultaneous Extended Altruistic Donor (Nead) Chains

Rees, Michael; Kopke, Jonathan E.; Pelletier, Raymond J.; Segev, Dana; Fabrega, Alfredo J.; Rogers, Jim; Pankewycz, O.; Roth, Aleda V.; Taber, Thomas D.; Unver, Utku; Nibhanupudy, B.; Leichtman, Alan B.; Buren, Charles T. Van; Young, Cynthia; Gallay, B.; Montgomery, Robert A.

doi:10.1097/00007890-201007272-00112

Cited by 3 publications

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“…Kidney‐paired donation programs have been successfully incorporating nondirected donors into nonsimultaneous extended (NEAD) chains (1). Including nondirected donors in either NEAD chains or domino‐paired donations (DPDs, chains that end in the waiting list rather than a bridge donor) increases match opportunities for incompatible pairs.…”

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The Honeymoon Phase and Studies of Nonsimultaneous Chains in Kidney-Paired Donation

Gentry

Segev

2011

American Journal of Transplantation

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Kidney-paired donation programs have been successfully incorporating nondirected donors into nonsimultaneous extended (NEAD) chains (1). Including nondirected donors in either NEAD chains or domino-paired donations (DPDs, chains that end in the waiting list rather than a bridge donor) increases match opportunities for incompatible pairs. When interpreting the performance of NEAD chain programs, though, we must recognize that the honeymoon phase (where many transplants are facilitated by a single donor) may not last forever. After the initial months or years of operation, bridge donors will accumulate, competing for scarce matches or dropping out altogether after long waits. Clinical experience in the longest-running registries also shows that many chains do not operate indefinitely, but dissipate as hard-to-match bridge donors languish.A recent report of Ashlagi et al. (2) highlights the need to recognize the honeymoon phase, as the data demonstrate that inferences from the early stages can be overturned and reversed as registries operate over longer periods of time. Ashlagi et al. reproduced our computational findings (3) that NEADs would not facilitate more transplants than DPDs over 24 periods, or months, of operation. Then, using 8-period simulations with longer segments (our simulation limited concurrent segments to three pairs without limiting overall chain length), Ashlagi et al. argued that NEADs with longer segments facilitate more transplants than DPDs. However, comparing Figure 2 with Figure 3 of their manuscript illustrates that the ostensibly minor detail of switching from a 24-period simulation to an 8-period simulation was actually the decisive factor in reversing the predicted benefit of DPDs over NEAD chains, not the longer segments.Our simulations showed that after 24 periods in mature registries, NEAD is not superior to DPD when segment lengths are limited to three. Figure 2 of Ashlagi et al. reproduces this result, with the endpoint of the NEAD-3 line below 1 (near 0.98). Figure 3 shows the opposite result for the exact same experiment when simulating only the first eight periods (the honeymoon phase): the endpoint of the NEAD-3 line in Figure 3 is above 1 (near 1.015). That is, NEAD chains seem superior to DPDs in Figure 3 but not in Figure 2, where the only difference is the number of periods simulated.Contrary to their honeymoon phase results, the data that Ashlagi et al. present actually prove that in mature registries, the advantage of DPD over NEAD is larger with chains that allow longer concurrent segments. Figure 2 compares DPD with NEAD for segments of length 4 and shows that for all renege rates, DPD gives an equal or greater number of transplants than NEAD. Figures 3-10 show valid data for honeymoon phase inferences, but cannot elucidate what will happen as NEAD chains deteriorate over time.Matching algorithms are also susceptible to the honeymoon phase problem. Ashlagi et al. limited their studies to only 8-period simulations because, as they stated, optimizing matches for later p...

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The Honeymoon Phase and Studies of Nonsimultaneous Chains in Kidney-Paired Donation

Gentry

Segev

2011

American Journal of Transplantation

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“…Rees et al; Ref. 4). The only multiregional‐paired donation program that does not utilize NEAD chains is the UNOS kidney‐paired donation pilot program (UNOS‐KPDPP).…”

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NEAD Chains in Transplantation

Ashlagi

Gilchrist

Roth

et al. 2011

American Journal of Transplantation

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Gentry and Segev (1) speculate above that the results reported in Ashlagi et al. (2), that nonsimultaneous extended altruistic donor (NEAD) chains produce more transplants than domino-paired donation (DPD), would be reversed if the computation were conducted for more periods. Here, we carry out the computation and show that, contrary to their conjecture, nonsimultaneous chains continue to allow more transplants than simultaneous chains, even over a longer time horizon. Furthermore, more highly sensitized patients are transplanted by allowing chains to continue with bridge donors rather than automatically ending with donations to patients on the deceased donor waiting list.Gentry et al. (3) used simulations to show that NEAD chains consisting of a maximum of three transplants in each period produce fewer transplants than simultaneous DPD chains over 24 periods. They restricted nonsimultaneous chains to have segments just as short as DPDs. This does not correspond to clinical practice: nonsimultaneous chains relieve the logistical constraints that arise when all surgeries must be performed simultaneously. Long NEAD chains have been successfully implemented in practice (e.g. Rees et al.; Ref. 4). The only multiregionalpaired donation program that does not utilize NEAD chains is the UNOS kidney-paired donation pilot program (UNOS-KPDPP). We respond to this letter providing data we hope will help change what we believe is a flawed UNOS policy.In Ref. (2), we found that allowing for longer chains reverses Gentry et al.'s result. Simulations in Ref. (2) involved only eight periods. Gentry and Segev assert in their letter that extending the simulation for more periods would reverse our results to agree with theirs. However, they do not carry out this computation, they only speculate about it. Figure 1 shows that this conjecture is not supported by actual simulations. We perform the simulations for unrestricted length chains for 24 or more periods and we refer to policies where NEAD chains and DPDs can be of any length in each period as NEAD-L and DPD-L chains. The vertical-axis is the ratio of the number of transplants conducted under a given policy compared to the number of transplants conducted under the restriction of a maximum of three transplants as imposed by Gentry et al. The horizontal-axis is the number of periods simulated. Figure 1A shows that NEAD chains not only produce more transplants than DPD chains, but also produce up to 25% more transplants for patients with panel reactive antibody (PRA) greater than 80%.Gentry and Segev did not address exogenous failure rates in their manuscript, nor in their letter. This omission is critical given the experience of real KPD programs. As of August 2011, the UNOS-KPDPP has transplanted only two people since starting in October 2010: more than 90% of the offers made by the UNOS-KPDPP have failed to culminate in transplants. Using an exogenous failure rate of only 15%, Figure 1B shows that NEAD-L chains produce 17% more transplants and nearly 30% more transplants for hi...

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Using Deceased-Donor Kidneys to Initiate Chains of Living Donor Kidney Paired Donations

Cornelio

Furian

Nicolò

et al. 2019

Proceedings of the 2019 AAAI/ACM Conference on AI, Ethics, and Society

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We design a flexible algorithm that exploits deceased donor kidneys to initiate chains of living donor kidney paired donations, combining deceased and living donor allocation mechanisms to improve the quantity and quality of kidney transplants. The advantages of this approach have been measured using retrospective data on the pool of donor/recipient incompatible and desensitized pairs at the Padua University Hospital, the largest center for living donor kidney transplants in Italy. The experiments show a remarkable improvement on the number of patients with incompatible donor who could be transplanted, a decrease in the number of desensitization procedures, and an increase in the number of UT patients (that is, patients unlikely to be transplanted for immunological reasons) in the waiting list who could receive an organ. Related worksThis paper contributes to the kidney exchange literature initiated by (Delmonico 2004;Delmonico et al. 2004a; arXiv:1901.02420v1 [q-bio.TO]

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Seven Non-Simultaneous Extended Altruistic Donor (Nead) Chains

Cited by 3 publications

References 0 publications

The Honeymoon Phase and Studies of Nonsimultaneous Chains in Kidney-Paired Donation

The Honeymoon Phase and Studies of Nonsimultaneous Chains in Kidney-Paired Donation

NEAD Chains in Transplantation

Using Deceased-Donor Kidneys to Initiate Chains of Living Donor Kidney Paired Donations

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