Historical Matching Strategies in Kidney Paired Donation: The 7-Year Evolution o

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http://onlinelibrary.wiley.com/store/10.1111/ajt.13337/asset/ajt13337.pdf?v=1&t=ijyt3kk8&s=68a6db9269a9a0748b398ad46443d421301bee69

Historical Matching Strategies in Kidney Paired Donation: The 7-Year Evolution of a Web-Based Virtual Matching System
D. E. Fumo, V. Kapoor, L. J. Reece, S. M. Stepkowski, J. E. Kopke, S. E. Rees, C. Smith, A. E. Roth, A. B. Leichtman and M. A. Rees
American Journal of Transplantation 2015; 15: 2646–2654
doi: 10.1111/ajt.13337

Introduction
Kidney paired donation (KPD) is an effective means of overcoming immunological barriers to living donor trans- plantation (1–12). The competition engendered by various paired donation registries has led to unique strategies and innovations (13). However, in order for KPD to reach its full potential in the United States, it has been suggested that larger pools, perhaps under a single national registry, would be beneficial (9,13–15). If a strong national registry is to be created, the best strategies from each registry should be adopted. This poses a challenge, however, as variations in outcome reporting make direct comparisons difficult.

Though progress has been made, matching algorithms continue to generate potential exchanges that ultimately fail to produce transplants. KPD registries have adopted one of two systems to deal with this problem: either attempt to rapidly move through offers until a success is found, or spend time creating more robust offers that have a higher likelihood of succeeding. Few programs have reported on this aspect of KPD (9). KPD registries that operate within a single center/system have fewer communication and financial barriers so that less time and effort are wasted in failed offers (16,17). For those registries that oversee multiple independent centers, sharing information requires the coordinated efforts of multiple individuals, and more time and energy are expended on failed offers in multi- institutional KPD programs than in those that operate as a single center.

Nondirected donors (NDD) have been utilized to start chains of KPD transplants that can be either simultaneous, called domino paired donation (DPD), or nonsimultaneous, called nonsimultaneous extended altruistic donor (NEAD) chains. In NEAD chains, a NDD starts a segment of a nonsimulta- neous series of transplants that ends with a bridge donor, who can start another segment to continue the NEAD chain at a later date (18). DPD eliminates the possibility of a bridge donor reneging by creating simultaneous KPD chains that end with a donation to a patient on the waiting list (8,19). The pros and cons of these approaches have been evaluated using simulated pools with real patient data, but actual experience is lacking (20–23).

Since its inception, the Alliance for Paired Donation (APD) has allowed simple cycles and NEAD chains to freely compete within its optimization algorithm and in converting computer-identified possible transplants, or ‘‘offers,’’ into completed transplants. In this study, we reviewed the efficacy of the APD matching system in converting computer-identified cycle and chain offers into completed transplants. Recognizing the observational nature of the evolution of the APD’s approach, the goals of the study were to: (i) determine the organization’s success rate over time; (ii) discern the reasons for failure to progress from an offer to successful transplants within different historical eras; (iii) compare the utility of cycles and chains of varying lengths; and (iv) correlate success rates with changes to matching software and procedures. We have also endeavored to delineate factors other than the matching algorithm, such as tissue typing standardization and communication between the APD and centers, that have impacted the matching process. The identified reasons for failure and the strategies employed to overcome these failures raise important practical and philosophical questions for discussion regard- ing future policy decisions for KPD in the United States.

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Three reasons for failure have occurred predictably, and were thus potentially preventable: (i) positive crossmatch; (ii) transplant center declined donor for medical reasons; and (iii) transplant center failed to deactivate donor transplanted outside the APD. These three MRFs accounted for 59% of all reasons for failure (Figure 4).

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…it became apparent that offers were failing because transplant centers were consistently rejecting potential donors for reasons that could have been specified and accounted for prospectively.

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Failures due to transplant centers rejecting donors remained relatively unchanged (18–19%)…

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…the percent of transplanted patients with a PRA >/= 80% has increased from 15.4% in 2007 to 36.0% in 2014.

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…it was apparent that transplant centers were rejecting donors for reasons that were not consistent across centers. For instance, one center would not accept a donor if there was more than a six-inch height discrepancy with the recipient, which was not the case with any other center.

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However, not unexpectedly, transplant centers have sometimes relaxed their exclusion criteria to avoid the possibility of denying a donor they might actually accept. For example, a center might normally exclude any donors over the age of 65, but would accept a 65-year-old donor who presented a zero-antigen mismatch and excellent renal function. Consequently, that transplant center might relax their exclusion criterion in all cases, to avoid unknowingly excluding one acceptable exception.

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On the whole, the diversity in strategies employed by the different KPD registries has been instrumental in the evolution of KPD in the United States. However, it is clear that the next phase in the process is the creation of a national registry (9,13–15).

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Finally, perhaps the biggest barrier to KPD success in the U.S. is not an issue that can be resolved by software or process changes. A recent article by Massie et al, suggests that an additional 1000 KPD transplants could be performed per year, and in agreement with a recent national consensus conference, identified financial barriers as one of the biggest obstacles to expanding KPD (13,34). Overcoming financial barriers would allow more centers to participate and more incompatible pairs to be enrolled, thus increasing the available pool size and allowing more patients to receive KPD transplants. To address this issue, several authors have suggested a national KPD ‘‘standard acquisition charge’’ approach, and the Alliance for Paired Donation recently received an Agency for Healthcare Research and Quality (AHRQ) grant to pilot such a project (13,15,36–38).