Characterization of waiting times in a simulation of kidney paired donation.

A national kidney paired donation (KPD) program will substantially increase transplant opportunities for recipients with blood type incompatible or cross-match positive donors. It seems likely that donor-recipient pairs with certain blood types, races or restrictions will wait longer than others for a match, although no data exist to confirm this assumption. We simulated patients and characterized the predicted waiting times for different blood type sub-groups, as well as the effects of patient-imposed restrictions on waiting time. We also compared waiting times of different racial sub-groups. Almost all patients with panel-reactive antibody (PRA) less than 80% match within a few months in a national KPD program, with the longest waiting time seen by O recipients with AB donors. Highly sensitized patients wait considerably longer, especially those unwilling to travel or accept older donors, and those with AB or B donors may not match in a timely manner. Although patients are better served by matching in a combined pool than within their own race, racial inequalities exist and bonus points can offset some of these differences. These data provide the first waiting time predictions that can aid patients with incompatible donors in choosing between KPD and desensitization, and can also facilitate planning for a national KPD program.