Geographic variation in utilization of deceased donor livers in the United States in the era of advanced perfusion

Abstract

Understanding the geographic variation in deceased donor liver utilization can guide allocation policy and technology implementation. Using US transplant registry data, we evaluated geographic differences in utilization by donor quality, policy era, and uptake of advanced perfusion (AP). This retrospective cohort included all liver donors and waitlisted patients from 2010 to September 2024. Donors were aggregated by Hospital Referral Region (HRR) and stratified by quality using the liver Discard Risk Index (DSRI). Exposures included the allocation policy era and increased use of AP technology (July 2022 onward). Observed-to-expected (O:E) ratios of liver non-utilization were calculated by HRR and modeled to reveal geographically contiguous low utilization clusters (LUCs). The proportion of HRRs within LUCs increased from 24% in Share 15 (S15), to 25% in Share 35 (S35), 32% in Acuity Circles (AC), and then decreased to 21% in the AP era ( p =0.01). There were 7 distinct LUCs in S15 (median non-utilization=33%), 7 LUCs in S35 (non-utilization=32%), 7 LUCs in AC (non-utilization=41%), and 3 LUCs in the AP era (non-utilization=46%). Donor quality by HRR decreased over time, with a median DSRI of 2.56 (IQR: 1.25-5.79) in S15 to 5.69 (2.01-35.30) in AP ( p <0.001). Accounting for DSRI, odds of non-utilization were highest in AC ( ref. Share 35 , OR=1.27, p <0.001), which decreased in AP (OR=1.06, p =0.001). Utilization of normothermic machine perfusion was associated with a markedly lower odds of discard (OR=0.03, 0.03-0.04; p <0.001). Livers originating from LUCs traveled shorter distances in each era other than S35. The number of net exporter HRRs in LUCs was equivalent to non-LUCs in each era, other than AP, where LUCs contained fewer net exporter HRRs [2 (3.2%) vs. 42 (17.4%), p =0.004]. On adjusted analysis, candidates in LUCs had a lower likelihood of transplant (HR=0.88, p <0.001) but also lower waitlist mortality (HR=0.95, p <0.001). The advent of advanced perfusion was associated with the utilization of otherwise marginal liver allografts and ameliorating geographic imbalances in discard seen with successive allocation policy eras.

Keywords: advanced perfusion; allocation policy; normothermic machine perfusion; organ procurement organizations; organ utilization.

Figure 1.. Observed to expected (O:E) non-utilization and Low Utilization Clusters (LUCs) over the study period.

A total of 10 LUCs were seen over the entire study period. Adjusting for donor quality, the risk of non-utilization within LUCs was 1.14 (1.07–1.24) vs. 0.95 outside of LUCs (0.83–1.03; p<0.001).

Figure 2.. Low utilization clusters (LUCs) by policy era and implementation of advanced perfusion.

There were 7 LUCs from Share 15 to Acuity Circles and 3 in the advanced perfusion era. However, the number of hospital referral regions (HRRs) within LUCs increased until the widespread implementation of advanced perfusion, with 73 in Share 15, 77 in Share 35, 98 in Acuity Circles, then 63 in the Advanced Perfusion era (p=0.011).