Paired Exchange Programs for Living Donors

Introduction

There are far more eligible kidney transplant candidates worldwide than there are organs available. Kidney exchange, also referred to as paired kidney donation, has become strongly established over the past decade as a modality for facilitating living kidney donation by donors who are not compatible with their intended recipients. Instead of donating directly to the intended recipient, candidate-donor pairs are matched together to participate in a mutually beneficial exchange of organs. This requires a coordinating effort to collect data about incompatible pairs and about other types of participants like nondirected (altruistic) donors and compatible pairs, and to select appropriate matches by a manual or algorithmic process.

In this chapter, we examine the common features and the idiosyncrasies of several successful paired exchange efforts around the world : in Korea, the Netherlands, Canada, Australia, India, the UK, the US, and other countries. Reviewing these differences may be reassuring for groups working to implement paired exchange, because for each potential snag that might have delayed or limited one program’s efforts, there are counterexamples in which that aspect of paired exchange was not an impediment.

Finding Exchange Opportunities

In every kidney exchange program, some incompatible pairs will fail to find an exchange opportunity. Because blood group O donors are most likely to be compatible with their recipients, there will be a blood group imbalance, with too few O donors for too many O recipients in any population of incompatible pairs. Populations of incompatible pairs also have larger numbers of highly sensitized candidates, who are difficult to match in an exchange. This imbalance limits exchange opportunities and leads to innovations like the inclusion of compatible pairs and nondirected donors, extending match arrangements to three or four or more pairs, and desensitization as part of the exchange program, all of which can enhance the proportion of incompatible pairs successfully transplanted.

Paired exchange may have the longest history in Korea, which established an exchange program in 1991. By 2003 exchanges comprised more than 10% of living kidney donation at one Korean center. Korea’s approach emphasized close human leukocyte antigen (HLA) matching between donors and recipients. Living donors were only accepted if they shared more than one DR antigen or two of four A/B antigens with their recipients. Of pairs deemed incompatible, 30% had HLA mismatching beyond these criteria, 65% were blood type incompatible, and only 5% had a positive crossmatch test. Compared with other programs that allow more HLA mismatch, this restriction may have directed more candidate/donor pairs into the exchange group, but may have ruled out more potential exchanges.

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