We aimed to compare liver transplant simulation projections to observed data before and after a major policy update. The current liver simulated allocation model (LSAM 2014) was used to simulate 1 year of liver transplants under rules from before and after implementation of Share35, which added full regional sharing for candidates with model for end-stage liver disease (MELD) scores of 35 or above. Results of these simulations were compared with actual data from SRTR's standard analysis files for the 1-year periods immediately before and after Share35 implementation on June 18, 2013. LSAM projected a minor decrease in rates of livers recovered for transplant but not transplanted (from 9.3% to 8.9%) and a decrease was observed in the actual data (from 10.1% to 9.5%, Table 1). LSAM overestimated the proportion of livers shared regionally under the pre-Share35 rules (28.6% regional sharing in LSAM vs. 20.4% observed) but correctly projected that regional sharing would increase under Share35 (33.5% projected vs. 31.8% observed, Table 2). LSAM projected an increase in transplant rates for MELD 35+ candidates from 862 to 1258 transplants per 100 patient-years, and an increase from 1085 to 1478 was observed. Finally, LSAM projected a slight decrease in waitlist death rates for MELD 35+ candidates from 105 to 100 deaths per 100 waitlist years and a decrease from 157 to 143 was observed. Implementation of Share35 presents a rare opportunity to evaluate LSAM projections against observed data across a policy-change boundary. LSAM correctly predicted the direction of change in most outcome categories of interest, although the magnitude of some changes was smaller than observed.

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