AIM: On 12/4/2014, the OPTN implemented a new KAS for deceased donor(DD) transplants which, among many changes, increased priority for highly sensitized (HS) candidates (cPRA>98%). Such candidates now have the highest priority for national (100%), regional (99%) and local (98%) sharing. While the new KAS stimulated broader sharing, it also created new logistical and time-sensitive challenges. In this study, we assessed the impact of the virtual crossmatch (vXM) under the new KAS.

Methods: Between 12/04/2014 and 9/30/2015, 129 kidney alone DD transplants were performed. For the HS recipients, we reviewed whether the transplant was performed based on a prospective, physical crossmatch (pXM) or vXM. The vXM was defined as the absence of donor specific antibody (MFI<1,000). For all vXM-vetted transplants, a pXM was performed concurrently or retrospectively. For all transplants, we reviewed graft function, incidence of early episodes of rejection and retrospective pXM results.

Results: During this time period, HS recipients received 43/129(33%) of the DD transplants. Among this group, 38/43(88%) received imported organs and 30/43(70%) were transplanted solely on a negative vXM. Mean follow up was 6.2 mos and mean serum Cr was 1.3. In no instance was the pXM unexpectedly positive due to HLA antibody. Most importantly, there were no instances of hyperacute or accelerated graft rejection among the HS recipients transplanted solely on a vXM. Interestingly, HS recipients were minorities (70%), female (72%), awaiting a first transplant (63%) and had a considerable degree of HLA mismatch (~1 Ag ea. A,B,C,DR,DQ).

Conclusions: Since implementation of the new KAS, centers are receiving more organ offers for HS candidates, often from centers at great distances. As such, there may be insufficient time to ship material for a pXM. Rather, centers must accept/decline offers solely on a vXM. Our data demonstrate that a vXM can identify HS candidates who may proceed safely to transplant without a prospective pXM. This approach minimizes cold ischemia time and improves allocation efficiency as evidenced by our increased transplant rate compared to the national average (33% vs ~14%). Limitations to the vXM include; incomplete/incorrect donor HLA type, lack of current serum or equivocal/weak DSAs. Nonetheless, the vXM clearly benefits the most highly sensitized candidates under the new KAS.

CITATION INFORMATION: Bray R, Parsons R, Turgeon N, Gebel H. Virtual Crossmatching Under the New KAS: Safely Bypassing a Physical Crossmatch When Allocating Kidneys to Highly Sensitized Candidates. Am J Transplant. 2016;16 (suppl 3).

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