We (now) know what we are, but not what we may be.

I the current issue of Transplantation, Bowring et al from Johns Hopkins University examine the impact of broader regional sharing on geographic disparity in access to liver transplantation. The investigators use Scientific Registry Transplant Recipients data on outcomes for waitlisted patients in the 4 years before and 4 years after the implementation of Share 35 liver allocation policy, and compare the rates of transplantation at different Model for End-Stage Liver Disease (MELD) scores based on the program of listing, the donor service area (DSA), and the region in these 2 time periods. Importantly, to reduce heterogeneity, the authors excluded patients with a MELD score <15, as well as centers with very few wait-listed patients or those which had transplanted fewer than 1 transplant per year during the study period. The authors utilized the median incidence rate ratio, a statistical method that allows comparison of the relative difference in the incidence rates of an event, in this case deceaseddonor liver transplantation. The main findings are that there are substantial differences in transplant rates across DSAs, and that this was impacted only very slightly by the implementation of Share 35. When looking at wait-listed candidates with MELD 35–40, the gap between in rates of transplantation actually widened, whereas it was reduced slightly for those with a MELD between 15 and 34. The authors examined the differences not only in DSA-level transplant but also in individual program-level transplant rates, which were substantial, yet less than DSAlevel differences. Importantly, the authors were able to separate program-level variation from DSA-level variation, so that heterogeneity across DSAs, a factor more directly impacted by organ allocation policy changes, can be assessed independently from any impact induced by program-level heterogeneity. These findings are not surprising, mainly because the goal of the Share 35 was not to decrease geographic disparity. Rather, Share 35 aimed to increase access to liver transplantation for candidates with the highest risk of death on the waitlist. The current study demonstrates that the relative rate of receiving a deceased donor liver transplant for patients with MELD scores 35 and above, in comparison to patients with MELD scores between 32 and 34, increased more than 2-fold after implementation of Share 35. Combining this observation with the same groups’ previous finding that the Share 35 policy resulted in a decrease in waitlist mortality of patients with MELD >35, it appears that the policy was a successful change to the allocation policy, albeit impacting mainly the sickest patients. As the current analysis did not investigate the changes in regional geographic disparity, it remains unknown whether regional sharing of the liver allografts altered the disparity within the regions after the implication of Share 35. This study provides an important benchmark of the current disparity in access to liver transplant even for the most urgent patients. The authors note that the revised liver allocation policy, which was approved by the Organ Procurement and Transplantation Network in December of 2017, would have expanded sharing by lowering the sharing threshold to MELD 32 and by adding an additional area of sharing beyond existing regional boundaries of 150 nautical mile circle around the donor hospital. The authors expressed concern that continued use of existing DSA and regional boundaries in the December of 2017 policy revision may not adequately address the geographic disparity. Importantly, however, the liver allocation policy approved in December of 2017 was met with a legal challenge due to the continued use of DSA and region as part of the policy, and thus was not implemented. In December of 2018, a new liver allocation policy was considered and approved by the Organ Procurement and Transplantation Network board that removes DSA and regional boundaries and instead uses a series of progressively larger concentric circles around the donor hospital for different MELD cohorts, starting with the highest MELD candidates. Following broad allocation for status 1 patients, the revised December 2018 policy will offer livers to candidates with a MELD 37–40 who are closest to the donor hospital (within 150 nautical mile circle). If there is no suitable patient within the 150-mile circle, then the circle will expand to 250 miles and again, if no suitable candidate, to 500 miles. Then the MELD threshold will reduce to 33–36 for candidates within 150, then to 250, and 500 nautical mile concentric circles, with the liver only being offered to the larger circle if there is not a suitable candidate within the smaller circle. This policy is anticipated to significantly reduce the disparity in access Commentary