HLA-B Matching Priority Removal in Transplantation Allocation: Was it Worth It?
Dr. Dorry Segev (DS), Transplant Surgeon from Johns Hopkins Medical Center, recently discussed the removal of HLA-B matching priority in transplantation with Dr. Kenar Jhaveri (eAJKD). Priority Points are assigned by the Organ Procurement and Transplantation Network (OPTN) to allocate deceased donor kidneys to transplant candidates who are on the active waiting list. Points are primarily given based on time of waiting; other points reflect sensitization, pediatric candidates, prior kidney donation, and quality of mismatch at A, B, and DR loci. Roberts et al in a paper published in NEJM in 2004 had predicted that removing HLA-B matching as a priority for the allocation of deceased-donor kidneys could reduce the existing racial imbalance by increasing the number of transplantations among nonwhites, with only a small increase in the rate of graft loss. As a result, HLA-B matching was removed from the priority system in anticipation that it would decrease the allocation disparity against African Americans. A study published in this issue of AJKD explored the effects of this new policy of removing HLA-B matching from the United States priority-points formula for allocating deceased-donor kidneys. The study found that the change partially eliminated the allocation disparity against African American recipients, but showed that a residual disparity still remained.
eAJKD: Why did you initiate this study?
DS: This was a study of the racial disparity between Caucasian and African American patients noted in kidney transplants in the United States before and after the recent allocation change in 2004 of HLA-B priority. We wondered whether eliminating the HLA-B matching accomplished what it was supposed to do – namely increase transplantation in African Americans in the United States and attenuate the disparity between racial groups. One would hope that HLA-B might have easily explained the African American disparity, and eliminating this matching priority would have corrected it, but this has not exactly happened. We went from a pre-policy difference of 37% lower rates to a post-policy difference of 23% lower rates. This is good, but not the complete reduction for which we hoped. Some other factors remain.
eAJKD: What other factors might cause this disparity?
DS: Many factors are possible, including the centers where African American patients are listed, co-morbid medical problems not captured by the UNOS database, higher propensity for declining organ offers, and provider bias in making organ offers. Also, the effect of a policy change may take longer to be fully realized than was captured in our study. We did see some evidence of this, as in the later years after the policy was changed, the disparity fell somewhat further to 19%.
eAJKD: Do you think other factors can be eliminated?
DS: The key is to figure out what is responsible for it. Right now, we are finishing a study where we have looked at center level factors in racial disparities. We hope this will provide some insight. There is ongoing work on cultural factors as well.
eAJKD: Does DR matching lead to racial disparities in organ allocation?
DS: There is always a balance between what you gain in terms of “outcomes” and utility, and what you lose in terms of “equity”. For HLA-B, Dr. Roberts and colleagues determined by simulation and outcome regression modeling that matching for HLA-B was not that important for improving outcomes, but did create an equity issue (allocation). Other simulations were done for HLA-DR, but found that DR matching had a bigger impact on outcome with less improvement on allocation.
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Anything that can be done to reduce the disparities for African Americans to get a deceased donor kidney is worthwhile. Further research to identify factors which could reduce these disparities and most importantly which are amenable to change is needed.