1. Analyzing Geographic Disparity in U.S. Heart Allocation System
Fatemeh Karami1, Mehdi Nayebpour2, Monica Gentili1,
Naoru Koizumi2, Andrew L. Rivard3
1Industrial Engineering, University of Louisville, Louisville, KY
2Schar School of Policy and Government, George Mason University, Arlington, VA
3Department of Radiology, Cleveland Clinic, Abu Dhabi
Background
Method and Data
In the United States, allocation of solid organs for transplantation is regulated and maintained by the United Network for Organ Sharing (UNOS).
Fifty-eight Organ Procurement Organizations (OPO) are responsible for evaluation and procurement of deceased-donor organs. UNOS recently approved a major nationwide change to the allocation algorithm of hearts for adult candidates into categories of severity status allocation for the most urgent candidates.
The Department of Health and Human Services Final Rule clearly states that ‘‘neither place of residence nor place of listing shall be a major determinant of access to a transplant” [1].
Based upon open access comments to the new algorithm; we hypothesize that the current allocation scheme contributes to geographic disparities.
Aim: Compare geographic disparities in access to heart transplant based on current policy vs. a proposed new 6-tier model with broader geographical allocation.
Method: We compared the transplant results of the two heart allocation models by simulating the policies using the Thoracic Simulated Allocation Model (TSAM).
Data: from UNOS data (age ≥ 18) containing 8434 adult patients needing only a heart transplant.
Disparity metrics: We measured disparity at the OPO level and at the regional level computing the following metrics:
Standard deviation
Range
Mean squared difference from the best rate (MSBR)
Interquartile range (20th – 80th)
Two OPOs had supply > greater than demand (green)
One OPO, supply = demand (*)
Three OPOs, had supply << demand (orange). *
Results
Geographic Disparities in Waiting Time to Transplantation
Geographic Disparities in Pre-Transplant Mortality Rate
Average of Total Waiting Time (days)
Current Policy
Proposed Policy
Mean
177
171
STD 56 60
MSBR
151
172
Range
230
286
Interquartile
range
176
174
The two policies have similar mean waiting times among OPOs.
Geographic disparities exists in both policies in terms of waiting time.
The proposed new policy increases geographic disparities in waiting time across OPOs.
The proposed new policy decreases geographic disparities for waiting time for Status 1B and Status 2.
The proposed policy increases geographic disparity in waiting time for Status 1A.
The proposed new policy decreases mortality rate for patients on the waiting list.
The proposed new policy decreases geographic disparity in pre-transplant mortality for status 1A patients across all OPOs.
Pre-Transplant Mortality Rate Across OPOs
Current Policy
Proposed Policy
Mean
0.07
0.03
STD
0.02
MSBR
0.045
Range 1
0.08
Interquartile range
0.05
Waiting Time to Transplantation Across OPOs for Proposed Policy
0 - 50
Geographic Disparities in Transplant Rate
Geographic Disparities in Distance Traveled by Organs
The two policies have similear mean waiting time among OPOs.
Geographic disparities exists in both policies in terms of transplant rate.
The proposed new policy increases geographic disparity in transplant rates across OPOs.
The proposed new policy increases geographic disparities of transplant rate for patients with different statuses.
Average Transplant Rate Across OPOs
Current Policy
Proposed Policy
Mean
0.56
0.59
STD
0.12
MSBR
0.22
0.25
Range
0.42
0.48
Interquartile
range
0.23
Transplant Rate Across OPOs for New Policy
The proposed 6 tier new policy increases the average distance that an organ will travel.
The proposed new policy increases geographic disparities that an organ travels across OPO boundries
Average Distance (Miles) Traveled by Organs in each Transplant Ctr
Current Policy
Proposed Policy
Mean
193
219
STD 87
105
MSBR
212
236
Range
412
684
Interquartile range
138
136
Discussion and Conclusions
References
XXdd
[1] DHHS. Organ Procurement and Transplantation Network; Final Rule (42 CFR Part 121). Federal Register 1998; 63(63): 16296–16338.
Disclosure Statement: No use of off-label and/or investigational drugs/devices in this study/presentation.
No relevant financial relationship exists for this study/presentation.
With the proposed new 6-tier policy; transplant rates, waiting times and pre-transplant mortality rates all improve.
With this 6-tier policy; the distance that organs will travel increases.
With the proposed 6-tier policy; overall geographic disparities in transplant rate, waiting time and average distance traveled by organs increase.