OR6 Increased reliance on the virtual crossmatch under the new kidney allocation schema (KAS)

Aim On 12/4/2014, the OPTN implemented a new KAS for deceased donor (DD) transplantation. Among the many changes was increased priority for highly sensitized (HS) candidates (cPRA≥99%). Such candidates now have the highest priority for national (100%) and regional (99%) sharing. Initial OPTN data indicate that these candidates receive ∼15% of all DD transplants. While the new KAS has introduced broader sharing, it has also presented new logistical and time-sensitive challenges. Therefore, we sought to assess the utility of the virtual crossmatch (vXM) in the new KAS. Methods Between 12/04/2014 and 3/27/2015, we performed 64 DD transplants. Among transplanted patients with cPRA ≥99%, we assessed 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. For all vXM-based transplants, we reviewed results of the retrospective pXM, graft function and episodes of early rejection. Results During this time period, 24/64 (37.5%) of the DD transplants were performed in HS candidates. Among this group, 23/24 (96%) kidneys were imported and 16 (66.6%) were transplanted solely on a prospective vXM to minimize cold ischemia time. For all vXM-based transplants, a pXM was performed concurrently with the transplant. 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 any of the HS candidates transplanted based on a vXM. Conclusions Due to the new KAS, centers are now receiving more organ offers for HS patients. Frequently, offers come from centers at great distances and often there is insufficient time to ship material for a prospective pXM. Rather, centers must accept or decline what may be a patient’s only opportunity for a compatible organ, solely on a vXM. Additionally, vXM-based transplantation minimizes cold ischemia time. Our data demonstrate that a vXM can identify HS candidates who can proceed safely to transplant without a prospective pXM. Limitations to performing a vXM include; incomplete/incorrect donor HLA type, lack of current patient serum or equivocal donor specific antibodies. Nonetheless, the vXM can prove beneficial for allocating organs to the most disadvantaged candidates.