Racial Disparities in Renal Allograft Survival: A Public Health Issue?

Long-term renal allograft survival in the United States: a critical reappraisal

Renal allograft survival has increased tremendously over past decades; this has been mostly attributed to improvements in first-year survival. This report describes the evolution of renal allograft survival in the United States where a total of 252 910 patients received a single-organ kidney transplant between 1989 and 2009. Half-lives were obtained from the Kaplan-Meier and Cox models. Graft half-life for deceased-donor transplants was 6.6 years in 1989, increased to 8 years in 1995, then after the year 2000 further increased to 8.8 years by 2005. More significant improvements were made in higher risk transplants like ECD recipients where the half-lives increased from 3 years in 1989 to 6.4 years in 2005. In low-risk populations like living-donor-recipients half-life did not change with 11.4 years in 1989 and 11.9 years in 2005. First-year attrition rates show dramatic improvements across all subgroups; however, attrition rates beyond the first year show only small improvements and are somewhat more evident in black recipients. The significant progress that has occurred over the last two decades in renal transplantation is mostly driven by improvements in short-term graft survival but long-term attrition is slowly improving and could lead to bigger advances in the future.

Inter-ethnic variability of three functional polymorphisms affecting the IMPDH2 gene

Human type II inosine monophosphate dehydrogenase (IMPDH2) is a key enzyme in the purine nucleotide biosynthetic pathway and constitutes a pivotal biological target for immunosuppressant and antiviral drugs. Several Single Nucleotide Polymorphisms (SNP) affecting the IMPDH2 gene sequence have been reported with potential functional relevance and could impact drugs response. We aimed to determine the frequency of three of these polymorphisms, namely g.3375C>T (Leu(263)Phe), c.-95T>G and IVS7+10T>C, in Caucasians, Tunisians, Peruvians and Black Africans (Gabonese and Senegalese). The g.3375C>T and c.-95T>G polymorphisms are rare with a Minor Allele Frequency ≤1.0% in our populations, whereas the third variant, IVS7+10T>C, is more frequent and displays large interethnic variations, with an allelic frequency ranging from 14.6% in the French Caucasian population studied to less than 2% in Black African and Peruvian populations. This ethnic-related data might contribute to a better understanding of the variability in clinical outcome and/or dose adjustments of drugs that are IMPDH inhibitors such as mycophenolic acid.

Racial and ethnic disparities in kidney transplantation

Success of renal transplantation, as a viable alternative to dialysis, has been tempered by long-standing racial disparities. Ethnic minorities have less access to transplantation, are less likely to be listed for transplantation, and experience a higher rate of graft failure. Reasons for the existing racial disparities at various stages of the transplantation process are complex and multi-factorial. They include a combination of behavioral, social, environmental, and occupational factors, as well as potential intended or unintended discrimination within the healthcare system. Immunologic factors such as human leukocyte antigen matching, composition of the organ donor pool, and patient immune response, all of which affect post-transplantation graft rejection rates and patient survival, also contribute to health disparities between ethnic groups.

Addressing racial and ethnic disparities in live donor kidney transplantation: priorities for research and intervention

One potential mechanism for reducing racial/ethnic disparities in the receipt of kidney transplants is to enhance minorities' pursuit of living donor kidney transplantation (LDKT). Pursuit of LDKT is influenced by patients' personal values, their extended social networks, the health care system, and the community at large. This review discusses research and interventions promoting LDKT, especially for minorities, including improving education for patients, donors, and providers, using LDKT kidneys more efficiently, and reducing surgical and financial barriers to transplant. Future directions to increase awareness of LDKT for more racial/ethnic minorities also are discussed including developing culturally tailored transplant education, clarifying transplant-eligibility practice guidelines, strengthening partnerships between community kidney providers and transplant centers, and conducting general media campaigns and community outreach.

Disparities in kidney transplant outcomes: a review

Sociocultural and socioeconomic disparities in graft survival, graft function, and patient survival in adult kidney transplant recipients are reviewed. Studies consistently document worse outcomes for black patients, patients with low income, and patients with less education, whereas better outcomes are reported in Hispanic and Asian kidney transplant recipients. However, the distinct roles of racial/ethnic versus socioeconomic factors remain unclear. Attention to potential pathways contributing to disparities has been limited to immunologic and nonimmunologic factors, for which the mechanisms have yet to be fully illuminated. Interventions to reduce disparities have focused on modifying immunosuppressant regimens. Modifying access to care and health care funding policies for immunosuppressive medication coverage also are discussed. The implementation of culturally sensitive approaches to the care of transplant candidates and recipients is promising. Future research is needed to examine the mechanisms contributing to disparities in graft survival and ultimately to intervene effectively.

Understanding disparities in transplantation: do social networks provide the missing clue?

Although the National Organ Transplant Act calls for equity in access to transplantation, scarcity and racial disparities persist. To date, even the most comprehensive models have been unable to adequately explain these racial disparities, leaving policymakers unsure how best to intervene. Previous individual-level analyses, which have implicated risk factors such as race, financial status, cultural beliefs, unemployment, lack of commitment to surgery and lack of continuous access to care, overlook contextual and social network exposures. Social networks present a compelling way to examine cumulative risk clustered across individuals. Social networks have been shown to influence health outcomes and health behaviors through various pathways, including shared social capital, engaging in similar or group risky behaviors, diffusion of information and adopting or propagating social norms. Precursors to chronic kidney disease, including obesity, have been shown to spread through social networks. Social network analysis can reveal shared risks between potential donors and recipients in a given network, clarifying the likelihood of finding an appropriate match through either direct donation or paired exchanges. This paper presents a novel application of social network analysis to transplantation, illustrating implications for disparities and future clinical interventions.

Black renal transplant recipients have poorer long-term graft survival than CYP3A5 expressers from other ethnic groups

BACKGROUND

African American transplant recipients have poorer long-term outcomes than Caucasian Americans. This difference was not found in French patients, suggesting socialized medicine overcame this disparity. It has also been hypothesized that the difference relates to the higher prevalence of Black individuals who express the metabolic enzyme cytochrome P4503A5 (CYP3A5), with consequent altered handling of immunosuppressive drugs.

METHODS

Records of 555 (50 Black; 505 non-Black) sequential renal transplant recipients from a single UK centre were analysed.

RESULTS

Outcomes were significantly worse for Black patients: death-censored graft survival (5-year 66% versus 87%, P = 0.001); halving of year one estimated glomerular filtration rate (mean 8.8 versus 10.8 years, P = 0.008); first-year graft loss (12% versus 3.8%, P = 0.02); and death-censored graft survival in patients surviving the first year with functioning grafts (5-year 77% versus 94%, P = 0.02). Death-censored 5-year graft survival was poorer in Black CYP3A5 expressers than in non-Black CYP3A5 expressers (62% versus 93%, P = 0.002). Following multivariate analysis, the Black group demonstrated poorer graft survival as compared to the non-Black group (hazard ratio 0.46, 95% CI 0.25-0.85, P = 0.002). In a subgroup of genotyped transplant recipients, ethnicity (hazard ratio 0.31, 95% CI 0.15-0.64, P = 0.002), and not CYP3A5 expresser status, persists as an independent risk factor for graft survival following multivariate analysis.

CONCLUSION

In this cohort of patients with socialized medicine, Black recipients had poorer long-term outcomes than individuals from other ethnic groups. This was independent of CYP3A5 expresser status.

African American kidney transplantation survival: the ability of immunosuppression to balance the inherent pre- and post-transplant risk factors

Among organ transplant recipients, the African American population historically has received special attention. This is because secondary to their disposition to certain disease states, for example hypertension, an African American patient has a propensity to reach end-stage renal disease and require renal replacement earlier than a Caucasian patient. Regardless of the initiative to replace dialysis therapy with organ transplantation, the African American patient has many barriers to kidney transplantation, thus extending their time on dialysis and waiting time on the organ transplant list. These factors are among the many negative causes of decreased kidney graft survival, realized before kidney transplantation. Unfortunately, once the African American recipient receives a kidney graft, the literature documents that many post-transplant barriers exist which limit successful outcomes. The primary post-transplant barrier relates to designing proper immunosuppression protocols. The difficulty in designing protocols revolves around (i) altered genetic metabolism/lower absorption, (ii) increased immuno-active cytokines and (iii) detrimental effects of noncompliance. Based on the literature, dosing of immunosuppression must be aggressive and requires a diligent practitioner. Research has indicated that, despite some success with proven levels of immunosuppression, the African American recipient usually requires a higher 'dose per weight' regimen. However, even with aggressive immunosuppressant dosing, African Americans still have worse outcomes than Caucasian recipients. Additionally, many of the targeted sites of action that immunosuppression exerts its effects on have been found to be amplified in the African American population. Finally, noncompliance is the most discouraging inhibitor of long-term success in organ transplantation. The consequences of noncompliance are biased by ethnicity and affect the African American population more severely. All of these factors are discussed further in this review in the hope of identifying an ideal healthcare model for caring for the African American transplant recipient, from diagnosing chronic kidney disease through to successful kidney graft outcomes. An indepth review of the literature is described and organized in a fashion that highlights all of the issues affecting success in African Americans. The compilation of the literature in this review will enable the reader to get closer to understanding the caveats of kidney transplantation in the African American patient, but falls short of delivering an actual 'equation' for post-transplant care in an African American kidney recipient.

Multicenter evaluation of a novel endothelial cell crossmatch test in kidney transplantation

BACKGROUND

Despite their clinical importance, clinical routine tests to detect anti-endothelial cell antibodies (AECA) in organ transplantation have not been readily available. This multicenter prospective kidney transplantation trial evaluates the efficacy of a novel endothelial cell crossmatch (ECXM) test to detect donor-reactive AECA associated with kidney allograft rejection.

METHODS

Pretransplant serum samples from 147 patients were tested for AECA by a novel flow cytometric crossmatch technique (XM-ONE) using peripheral blood endothelial progenitor cells as targets. Patient enrolment was based on acceptance for transplantation determined by donor lymphocyte crossmatch results.

RESULTS

Donor-reactive AECA were found in 35 of 147 (24%) patients. A significantly higher proportion of patients with a positive ECXM had rejections (16 of 35, 46%) during the follow-up of at least 3 months compared with those without AECA (13 of 112, 12%; P<0.00005). Both IgG and IgM AECAs were associated with graft rejections. Mean serum creatinine levels were significantly higher in patients with a positive ECXM test at 3 and 6 months posttransplant.

CONCLUSIONS

XM-ONE is quick, easy to perform on whole blood samples and identifies patients at risk for rejection and reduced graft function not identified by conventional lymphocyte crossmatches.

Socioeconomic position and graft failure in pediatric heart transplant recipients

BACKGROUND

Socioeconomic (SE) position may affect availability of resources, health-related behavior, and outcomes. We assessed whether patient SE position, determined for the block group of patient residence (average population 1000, smallest census unit with SE data), is associated with graft failure in pediatric heart transplant recipients.

METHODS AND RESULTS

We used the US Census 2000 database to derive a composite SE score for the block group of residence for all patients who underwent their first heart transplant at Children's Hospital Boston between 1991 and 2005 (n=135). Cox proportional hazards models were used to determine the risk of graft failure (death or retransplant) in the lowest tertile SE group (low SE group) compared with the remaining 2 of 3 patients (controls). The 2 groups were similar with respect to age, gender, diagnosis, and year of transplant. White race was less frequent in low SE group (64% versus 90%, P=0.001). Graft failure occurred in 46 transplant recipients (40 deaths, 6 retransplant). Low SE group (hazard ratio 2.4, 95% CI 1.3 to 4.3) and nonwhite race (hazard ratio 2.7, 95% CI 1.4 to 5.2) were both associated with higher risk of graft failure. In a multivariable model controlling for diagnosis and pretransplant support, race, and low SE position (hazard ratio 2.0, 95% CI 1.0 to 3.7, P=0.04) remained associated with graft failure. Low SE position group had a higher incidence rate of graft rejection and was at a higher risk of late rejection.

CONCLUSIONS

Low SE position may be an independent risk factor for graft failure in pediatric heart transplant recipients.

Framing disparities along the continuum of care from chronic kidney disease to transplantation: barriers and interventions

Research in renal transplantation continues to document scores of disparities affecting vulnerable populations at various stages along the transplantation process. Given that both biological and environmental determinants contribute significantly to variation, identifying factors underlying an unfairly biased distribution of the disease burden is crucial. Confounded definitions and gaps in understanding causal pathways impede effectiveness of interventions aimed at alleviating disparities. This article offers an operational definition of disparities in the context of a framework aimed at facilitating interventional research. Utilizing an original framework describing the entire continuum of the transplant process from diagnosis of chronic kidney disease through successful transplant, this article explores the case of racial disparities, illustrating key factors predicting and perpetuating disparities. Though gaps in current research leave us unable to identify which stages of the transplant pathway adversely affect most people, by identifying key risk factors across the continuum of care, this article highlights areas suited for targeted interventions and presents recommendations for improvement and future research.

Racial disparity trends for graft failure in the US pediatric kidney transplant population, 1980-2004

Graft survival among adult African American kidney transplant patients remains low compared to whites, but little information is available for children and adolescents. We examined trends in graft failure among US incident primary kidney transplant patients aged <19 years (n = 13 692), 1980-2004. Trends in 1-year and 2- to 5-year graft failure (for patients whose grafts survived the first year) were analyzed in 5-year intervals. One-year graft failure declined 70% for white and 77% for African American patients over the 25-year period, and 1-year graft failure rates improved at a slightly higher rate for African American compared to white patients (p = 0.02). In contrast, the graft failure rates for years 2-5 declined 53% for white and only 41% for African American patients over the 25 years (p = 0.29). In fully adjusted Cox proportional hazards analysis, the rate of graft failure among African Americans was approximately 2-fold higher than for white patients over the entire study period. Graft survival has improved slightly more for African American than white pediatric patients over the past 25 years. However, graft survival for African American pediatric patients remains poor compared with white patients.

Disparity in outcomes of surgical revascularization for limb salvage: race and gender are synergistic determinants of vein graft failure and limb loss

BACKGROUND

Vein bypass surgery is an effective therapy for atherosclerotic occlusive disease in the coronary and peripheral circulations; however, long-term results are limited by progressive attrition of graft patency. Failure of vein bypass grafts in patients with critical limb ischemia results in morbidity, limb loss, and additional resource use. Although technical factors are known to be critical to the success of surgical revascularization, patient-specific risk factors are not well defined. In particular, the relationship of race/ethnicity and gender to the outcomes of peripheral bypass surgery has been controversial.

METHODS AND RESULTS

We analyzed the Project of Ex Vivo Vein Graft Engineering via Transfection III (PREVENT III) randomized trial database, which included 1404 lower extremity vein graft operations performed exclusively for critical limb ischemia at 83 North American centers. Trial design included intensive ultrasound surveillance of the bypass graft and clinical follow-up to 1 year. Multivariable modeling (Cox proportional hazards and propensity score) was used to examine the relationships of demographic variables to clinical end points, including perioperative (30-day) events and 1-year outcomes (vein graft patency, limb salvage, and patient survival). Final propensity score models adjusted for 16 covariates (including type of institution, technical factors, selected comorbidities, and adjunctive medications) to examine the associations between race, gender, and outcomes. Among the 249 black patients enrolled in PREVENT III, 118 were women and 131 were men. Black men were at increased risk for early graft failure (hazard ratio [HR], 2.832 for 30-day failure; 95% confidence interval [CI], 1.393 to 5.759; P=0.0004), even when the analysis was restricted to exclude high-risk venous conduits. Black patients experienced reduced secondary patency (HR, 1.49; 95% CI, 1.08 to 2.06; P=0.016) and limb salvage (HR, 2.02; 95% CI, 1.27 to 3.20; P=0.003) at 1 year. Propensity score models demonstrate that black women were the most disadvantaged, with an increased risk for loss of graft patency (HR, 2.02 for secondary patency; 95% CI, 1.27 to 3.20; P=0.003) and major amputation (HR, 2.38; 95% CI, 1.18 to 4.83; P=0.016) at 1 year. Perioperative mortality and 1-year mortality were similar across race/gender groups.

CONCLUSIONS

Black race and female gender are risk factors for adverse outcomes after vein bypass surgery for limb salvage. Graft failure and limb loss are more common events in black patients, with black women being a particularly high-risk group. These data suggest the possibility of an altered biological response to vein grafting in this population; however, further studies are needed to determine the mechanisms underlying these observed disparities in outcome.

Assessment of racial disparities in chronic kidney disease stage 3 and 4 care in the department of defense health system

BACKGROUND AND OBJECTIVES

Racial disparities in provision of healthcare are widespread in the United States but have not been specifically assessed in provision of chronic kidney disease (CKD) care.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

We conducted a retrospective cohort study of the clinical database used in a Department of Defense (DOD) medical system. Beneficiaries studied were DOD-eligible beneficiaries with CKD stage 3 (n = 7729) and 4 (n = 589) using the modified Modification of Diet in Renal Disease (MDRD)-estimated GFR formula but requiring manual correction for Black race. Compliance with selected Kidney Disease Outcomes Quality Initiative (KDOQI) CKD recommended targets (monitoring of recommended laboratory data, prescription of recommended medications, and referral to nephrology) was assessed over a 12-mo period, stratified by CKD stage. Logistic regression analysis was used to assess whether race (White, Black, or other) was independently associated with provider compliance with targets, adjusted for demographic factors and burden of comorbid conditions.

RESULTS

Among the targets, only monitoring of LDL cholesterol was significantly less common among Blacks. For all other measures, compliance was either not significantly different or significantly higher for Black compared with White beneficiaries. However, patients categorized as "Other" race were in general less likely to achieve targets than Whites, and at stage 3 CKD significantly less likely to achieve targets for monitoring of phosphorous, hemoglobin, and vitamin D.

CONCLUSIONS

In the DOD health system, provider compliance with selected CKD stage 3 and 4 targets was not significantly lower for Black beneficiaries than for Whites, with the exception of LDL cholesterol monitoring. Patients classified as Other race were generally less likely to achieve targets than Whites, in some patients significantly so.