Improving Access to HLA-Matched Kidney Transplants for African American Patients

Diversity, equity, inclusion, and belonging in organ transplantation

Diversity, equity, inclusion, and belonging (DEIB) have implications for transplant access and outcomes. Inequities in transplantation have been identified over the years for minoritized groups based on race, ethnicity, sex, sexual orientation, gender identity, disability status, and other sociocultural identities. While DEIB initiatives have demonstrated success in improving transplant outcomes for some minoritized groups, many gaps still exist, and additional work is needed. Concerns about these practices have also been raised, and they may create barriers to achieving DEIB goals. This underscores the importance of transplant organizational commitment to practices that uphold the values of DEIB, as such efforts are effective in reducing transplant inequities and fostering an inclusive community. From this viewpoint, we reviewed the existing inequalities in transplant, importance of DEIB, common concerns about DEIB initiatives, and commitment of the American Society of Transplant to DEIB initiatives, including the foundation of Inclusion, Diversity, Equity, and Access to Life (IDEAL) committee. Recommendations for cultivating DEIB practices, as well as tips for managing backlash against DEIB initiatives, are also provided. All professionals within the field of transplantation should carefully consider these recommendations to help promote an inclusive community for patients, providers, and all key stakeholders.

Racial Disparities in Hospitalization Rates During Long-Term Follow-Up After Deceased-Donor Kidney Transplantation

OBJECTIVE

To compare hospitalization rates between African American (AA) and European American (EA) deceased-donor (DD) kidney transplant (KT) recipients during over a10-year period.

METHOD

Data from the Scientific Registry of Transplant Recipients and social determinants of health (SDoH), measured by the Social Deprivation Index, were used. Hospitalization rates were estimated for kidney recipients from AA and EA DDs who had one kidney transplanted into an AA and one into an EA, leading to four donor/recipient pairs (DRPs): AA/AA, AA/EA, EA/AA, and EA/EA. Poisson-Gamma models were fitted to assess post-transplant hospitalizations.

RESULT

Unadjusted hospitalization rates (95% confidence interval) were higher among all DRP involving AA, 131.1 (122.5, 140.3), 134.8 (126.3, 143.8), and 102.4 (98.9, 106.0) for AA/AA, AA/EA, and EA/AA, respectively, compared to 97.1 (93.7, 100.6) per 1000 post-transplant person-years for EA/EA pairs. Multivariable analysis showed u-shaped relationships across SDoH levels within each DRP, but findings varied depending on recipients' race, i.e., AA recipients in areas with the worst SDoH had higher hospitalization rates. However, EA recipients in areas with the best SDoH had higher hospitalization rates than their counterparts.

CONCLUSIONS

Relationship between healthcare utilization and SDoH depends on DRP, with higher hospitalization rates among AA recipients living in areas with the worst SDoH and among EA recipients in areas with the best SDoH profiles. SDoH plays an important role in driving disparities in hospitalizations after kidney transplantation.

Potential of new 250-nautical mile concentric circle allocation system for improving the donor/recipient HLA matching: Development of new matching algorithm

BACKGROUND

High-resolution typing of human leukocyte antigen (HLA) may revolutionize the field of kidney transplantation by selection of low immunogenic grafts. The new 250-nautical mile circle allocation system offers a unique opportunity to find low HLA immunogenic donors for eligible recipients.

METHODS

501 transplant candidates from the University of Toledo Medical Center (UTMC) between 2015 and 2019, registered at the Scientific Registry of Transplant Recipients (SRTR) were virtually matched to 4812 donors procured within 250-nautical miles using an in-house-developed simulation algorithm. Immunogenicity of HMS (hydrophobic mismatch score) ≤10 was measured based on imputed high-resolution HLAs. Simulated "optimal" matches with a KDPI≤50 % were compared with the transplant cohort between 2000 and 2010 with their kidney allograft survivals.

RESULTS

Out of 501 recipients 500 (99.8 %) were matched with donors ≤10 HMS and KDPI ≤50 %. The average HMS value for simulated transplants was 1.4 (range 0-10) versus 6.3 (range 0-75) in the retrospective cohort (p < 0.001). The simulated model had a median mismatch number of 3/6, while the reference cohort 4/6 among HLA-A/B/DR antigens (p < 0.001). The estimated median graft survival was 18.2 years for the simulated cohort vs. 13.4 years in the real-life cohort (p < 0.001), gaining 4.9 years per transplant and 2450 survival years for all patients. For year 2014, out of 98 patients and 659 donors, each recipient had a median number of 141 donors (HMS < 10; range 8-378). Similar values were found for patients between 2015 and 2019.

CONCLUSION

Donors within 250-nautical miles proffers excellent and multiple options for finding well-matched low immunogenic HLA kidney donors for UTMC patients, thus significantly improving their chances for long-term allograft survival.

HLA EPLET Frequencies Are Similar in Six Population Groups and Are Expressed by the Most Common HLA Alleles

The degree of immunological compatibility between donors and recipients greatly impacts allograft survival. In the United States kidney allocation system, HLA antigen-level matching has been shown to cause ethnic disparities and thus, has been de-emphasised. However, priority points are still awarded for antigen-level zero-ABDR matching, zero-DR matching and one-DR matching. Recently, the degree of HLA molecular (eplet) mismatch has emerged as a more accurate measure of immunological risk, and eplet mismatch load has gained attention as a possible biomarker to improve HLA compatibility. However, little is known about the frequency of eplets in population groups, which is a necessary step to ensure that candidates from any ethnical background can have similar chances at a well-matched organ. Eplet frequencies were estimated using HLA alleles in the Common, Intermediate and Well-Documented (CIWD) 3.0.0 catalogue for six population groups: African-American (AFA), Asian-Pacific Islander (API), European/European descent (EURO), Middle East/North Coast of Africa (MENA), Hispanic/Latino (HIS) and Native-American (NAM). We determined that 98.6% (484 out of 491) of HLA eplets are expressed by the common HLA alleles in all population groups. Of the seven eplets that were expressed by less common HLA alleles, six were Class I eplets and one was expressed by HLA-DQB1 alleles and most were expressed by HLA alleles that were more commonly observed in European/European descent populations. Our observations indicate that HLA eplets will not cause any significant disparity if applied to HLA molecular compatibility, regardless of the ethnic origin of both recipients and donors.

Highly Sensitized Kidney Transplant Outcomes After the 2014 Kidney Allocation System Change

Introduction: Kidney Allocation System (KAS) was implemented by United Network for Organ Sharing in 2014 to reduce allocation disparities. Research Questions: Outcomes of highly sensitized patients (calculated panel reactive antibody (cPRA) ≥ 97%) before and after KAS were compared to low-risk recipients (cPRA <10%) in the post-KAS era were examined. The impact on racial disparities was determined. Design: This was a retrospective study of national registry data. Two cohorts of adult candidates waitlisted for deceased donor transplantation during 3-year periods before and after KAS were identified. Results: Highly sensitized patients (N = 1238 and 4687) received a deceased donor kidney transplant between January 1, 2011 and December 31, 2013 and between January 1, 2015 and December, 31, 2017. Racial disparity for highly sensitized patients improved, yet remained significant (P < 0.001), with Black patients comprising 40% and 41% of the highly sensitized candidates and 28% and 34% of the recipients pre- and post-KAS. While posttransplant death-censored graft failure for highly sensitized recipients was similar overall, post-KAS was associated with improved graft survival in the first year after transplant (HR 0.56, 95% CI 0.40-0.78). When compared to contemporaneous lowrisk recipients, both death-censored and all-cause graft failure were similar for highly sensitized recipients and was associated with increased risk for death-censored graft failure beyond the first year (HR 1.39, 95% CI 1.11-1.73). Conclusion: The allocation system led to an increase in transplantation in highly sensitized candidates without compromising outcomes. Although KAS has led to more balanced transplant rates between highly sensitized Black and White patients, racial inequalities persist.

Maximizing matching, equity and survival in kidney transplantation using molecular HLA immunogenicity quantitation

HLA matching improves long-term outcomes of kidney transplantation, yet implementation challenges persist, particularly within the African American (Black) patient demographic due to donor scarcity. Consequently, kidney survival rates among Black patients significantly lag behind those of other racial groups. A refined matching scheme holds promise for improving kidney survival, with prioritized matching for Black patients potentially bolstering rates of HLA-matched transplants. To facilitate quantity, quality and equity in kidney transplants, we propose two matching algorithms based on quantification of HLA immunogenicity using the hydrophobic mismatch score (HMS) for prospective transplants. We mined the national transplant patient database (SRTR) for a diverse group of donors and recipients with known racial backgrounds. Additionally, we use novel methods to infer survival assessment in the simulated transplants generated by our matching algorithms, in the absence of actual target outcomes, utilizing modified unsupervised clustering techniques. Our allocation algorithms demonstrated the ability to match 87.7% of Black and 86.1% of White recipients under the HLA immunogenicity threshold of 10. Notably, at the lowest HMS threshold of 0, 4.4% of Black and 12.1% of White recipients were matched, a marked increase from the 1.8% and 6.6% matched under the prevailing allocation scheme. Furthermore, our allocation algorithms yielded similar or improved survival rates, as illustrated by Kaplan-Meier (KM) curves, and enhanced survival prediction accuracy, evidenced by C-indices and Integrated Brier Scores.

Canadian Kidney Transplant Professionals' Perspectives on Precision Medicine and Molecular Matching in Kidney Allocation

Background

Antibody-mediated rejection is an important cause of kidney transplant loss. A new strategy requiring application of precision medicine tools in transplantation considers molecular compatibility between donors and recipients and holds the promise of improved immunologic risk, preventing rejection and premature graft loss. The objective of this study was to gather Canadian transplant professionals' perspectives on molecular compatibility in kidney transplantation.

Methods

Seventeen Canadian transplant professionals (14 nephrologists, 2 nurses, and 1 surgeon) participated in semistructured interviews in 2021. The interviews were digitally recorded, transcribed, and analyzed using the qualitative description approach.

Results

Participants identified fair access to transplantation as the most important principle in kidney allocation. Molecular compatibility was viewed as a promising innovation. However, participants were concerned about increased waiting times, negative impact on some patients, and potential problems related to the adequacy of information explaining this new technology. To mitigate the challenges associated with molecular matching, participants suggested integrating a maximum waiting time for molecular-matched kidneys and expanding the program nationally/internationally.

Conclusions

Molecular matching in kidney transplantation is viewed as a promising technology for decreasing the incidence of antibody-mediated rejection and improving graft survival. Further studies are needed to determine how to ethically integrate this technology into the kidney allocation algorithm.

Association of Recipient APOL1 Kidney Risk Alleles With Kidney Transplant Outcomes

BACKGROUND

Kidney transplant survival in African American recipients is lower compared with non-African American transplant recipients. APOL1 risk alleles (RA) have been postulated as likely contributors. We examined the graft outcomes in kidney transplant recipients (KTRs) stratified by APOL1 RA status in a multicenter observational prospective study.

METHODS

The Renal Transplant Outcome Study recruited a cohort of incident KTRs at 3 transplant centers in the Philadelphia area from 1999-2004. KTRs were genotyped for APOL1 RA. Allograft and patient survival rates were compared by the presence and number of APOL1 RA.

RESULTS

Among 221 participants, approximately 43% carried 2 APOL1 RA. Recipients carrying 2 APOL1 RA demonstrated lower graft survival compared with recipients with only 1 or none of APOL1 RA at 1 y posttransplant, independently of other donor and recipient characteristics (adjusted hazard ratio 3.2 [95% confidence interval, 1.0-10.4], P  = 0.05). There was no significant difference in overall survival or graft survival after 3 y posttransplantation. There was no difference in death by APOL1 -risk status ( P  = 0.11).

CONCLUSIONS

Recipients with 2 APOL1 high-risk alleles exhibited lower graft survival 1 y posttransplantation compared with recipients with only 1 or 0 APOL1 RA. Further research is required to study the combined role of the recipient and donor APOL1 genotypes in kidney transplantation.

Comparative Study of the Impact of Human Leukocyte Antigens on Renal Transplant Survival in Andalusia and the United States

Renal transplantation is the treatment of choice for patients suffering from chronic renal disease, one of the leading causes of death worldwide. Among the biological barriers that may increase the risk of acute renal graft rejection is the presence of human leukocyte antigen (HLA) incompatibilities between donor and recipient. This work presents a comparative study of the influence of HLA incompatibilities on renal transplantation survival in the Andalusian (South of Spain) and United States (US) population. The main objective is to analyse the extent to which results about the influence of different factors on renal graft survival can be generalised to different populations. The Kaplan-Meier estimator and the Cox model have been used to identify and quantify the impact on the survival probability of HLA incompatibilities, both in isolation and in conjunction with other factors associated with the donor and recipient. According to the results obtained, HLA incompatibilities considered in isolation have negligible impact on renal survival in the Andalusian population and a moderate impact in the US population. Grouping by HLA score presents some similarities for both populations, while the sum of all HLA scores (aHLA) only has an impact on the US population. Finally, the graft survival probability of the two populations differs when aHLA is considered in conjunction with blood type. The results suggest that the disparities in the renal graft survival probability between the two populations under study are due not only to biological and transplantation-associated factors, but also to social-health factors and ethnic heterogeneity between populations.