Declining influence of race on the outcome of living-donor renal transplantation

The Impact of Recipient Demographics on Outcomes from Living Donor Kidneys: Systematic Review and Meta-Analysis

Background and Aims: Recipient demographics affect outcomes after kidney transplantation. The aim of this study was to assess, for kidneys retrieved from living donors, the effect of recipient sex, ethnicity, and body mass index (BMI) on delayed graft function (DGF) and one-year graft function, incidence of acute rejection (AR), and recipient and graft survivals. Methods: A systematic review and meta-analysis was performed. EMBASE and MEDLINE databases were searched using algorithms through Ovid. Web of Science collection, BIOSIS, CABI, Korean Journal database, Russian Science Citation Index, and SciELO were searched through Web of Science. Cochrane database was also searched. Risk of bias was assessed using the NHBLI tools. Data analysis was performed using Revman 5.4. Mean difference (MD) and risk ratio (RR) were used in analysis. Results: A total of 5129 studies were identified; 24 studies met the inclusion criteria and were analysed. Female recipients were found to have a significantly lower serum creatinine 1-year-post renal transplantation (MD: −0.24 mg/dL 95%CI: −0.18 to −0.29 p < 0.01) compared to male recipients. No significant difference in survival between male and female recipients nor between Caucasians and Africans was observed (p = 0.08). However, Caucasian recipients had a higher 1-year graft survival compared to African recipients (95% CI 0.52−0.98) with also a lower incidence of DGF (RR = 0.63 p < 0.01) and AR (RR = 0.55 p < 0.01). Recipient obesity (BMI > 30) was found to have no effect on 1-year recipient (p = 0.28) and graft survival (p = 0.93) compared to non-obese recipients although non-obese recipients had a lower rate of DGF (RR = 0.65 p < 0.01) and AR (RR = 0.81 p < 0.01) compared to obese recipients. Conclusions: Gender mismatch between male recipients and female donors has negative impact on graft survival. African ethnicity and obesity do not to influence recipient and graft survival but negatively affect DGF and AR rates.

Black Ethnicity is Not a Risk Factor for Mortality or Graft Loss After Kidney Transplant in the United Kingdom

OBJECTIVES

There are conflicting reports in the literature regarding outcomes after kidney transplant for patients of black ethnicity. To investigate further, we compared outcomes for black versus white kidney transplant recipients in a single UK transplant center.

MATERIALS AND METHODS

We analyzed 1066 kidney transplant recipients (80 black patients, 986 white patients) within a single-center cohort (2007-2017) in the United Kingdom, with cumulative 4446 patient-year follow-up. Data were electronically extracted from the Department of Health Informatics database for every study recruit, with manual data linkage to the UK Transplant Registry (for graft survival, delayed graft function, and rejection data) and Office for National Statistics (for mortality data). Primary outcomes of interest were graft/patient survival.

RESULTS

Black recipients have increased baseline risk profiles with longer wait times, difficulty in matching, worse HLA matching, more socioeconomic deprivation, and lower rates of living kidney donors. Postoperatively, black versus white recipients had increased risk for delayed graft function (34.3% vs 10.2%; P < .001), increased 1-year rejection (16.7% vs 7.3%; P = .012), higher 1-year creatinine levels (166 vs 138 mmol/L; P = .003), and longer posttransplant length of stay (14.5 vs 9.5 days; P = .020). Although black recipients did not have increased risk of death versus white recipients (10.0% vs 11.0%, respectively; P = .486), they did have increased risk for death-censored graft loss (23.8% vs 11.1%; P = .002). However, in an adjusted Cox regression model, black ethnicity was not associated with increased risk for death-censored graft loss (hazard ratio of 1.209, 95% confidence interval, 0.660-2.216; P = .539).

CONCLUSIONS

Black kidney transplant recipients in the United Kingdom have increased risk of adverse graft-related outcomes due to high-risk baseline variables rather than their black ethnicity per se.

Do outcomes after kidney transplantation differ for black patients in England versus New York State? A comparative, population-cohort analysis

OBJECTIVES

Inferior outcomes for black kidney transplant recipients in the USA may not be generalisable elsewhere. In this population cohort analysis, we compared outcomes for black kidney transplant patients in England versus New York State.

DESIGN

Retrospective, comparative, population cohort study utilising administrative data registries.

SETTINGS AND PARTICIPANTS

English data were derived from Hospital Episode Statistics, while New York State data were derived from Statewide Planning and Research Cooperative System. All adults receiving their first kidney-alone allograft between 2003 and 2013 were eligible for inclusion.

MEASURES

The primary outcome measure was mortality post kidney transplantation (including inhospital death, 30-day mortality and 1-year mortality). Secondary outcome measures included postoperative admission length of stay, risk of rehospitalisation, development of cardiac events, stroke, cancer or fracture and finally transplant rejection/failure. Cox proportional hazards regression was used to investigate relationship between ethnicity, country and outcome.

RESULTS

Black patients comprised 6.5% of the English cohort (n=1215/18 493) and 23.0% of the New York State cohort (n=2660/11 602). Compared with New York State, black kidney transplant recipients in England were more likely younger, male, living-donor kidney recipients and had dissimilar medical comorbidities. Inpatient mortality was not statistically different, but death within 30 days, 1 year or kidney transplant rejection/failure was lower among black patients in England versus black patients in New York State. In adjusted regression analysis, with black ethnicity the reference group, white patients had reduced risk for 30-day mortality (OR 0.62 (95% CI 0.44 to 0.86)) and 1-year mortality (OR 0.79 (95% CI 0.63 to 0.99)) in New York State but no difference was observed in England. Compared with England, black kidney transplant patients in New York State had increased HR for kidney transplant rejection rejection/failure by median follow-up (HR 2.15, 95% CI 1.91 to 2.43).

CONCLUSIONS

Outcomes after kidney transplantation for black patients may not be translatable between countries.

Lower kidney allograft survival in African-Americans compared to Hispanic-Americans with lupus

Background and objective African-Americans and Hispanic-Americans with lupus are the two most common minority groups who receive kidney transplants in the USA. It is unknown if African-Americans and Hispanic-Americans with lupus have similar outcomes after kidney transplantation. In this study, we assessed whether African-Americans compared to Hispanic-Americans have worse kidney allograft survival after risk factors of rejection and other prognostic factors were matched between both groups. Methods Out of 1816 African-Americans and 901 Hispanic-Americans with lupus, who received kidney transplants between 1987 and 2006 and had complete records in the UNOS program, 478 pairs were matched in 16 baseline predictors and follow-up time employing a predicted probability of group membership. The primary outcome was kidney allograft survival. Main secondary outcomes were rejection, allograft failure attributed to rejection, and mortality. Results Matched pairs were predominantly women (81%) with the mean age of 36 years. 96% were on dialysis before transplantation. 89% of recipients received kidneys from deceased donors and 15.5% from expanded criteria donors. 12% of recipients had zero HLA mismatch. African-Americans compared to Hispanic-Americans had lower cumulative allograft survival during 12-year follow-up ( p < 0.001). African-Americans compared to Hispanic-Americans had higher rates of rejection (10.4 vs 6.73 events/100 patients-years; p = 0.0002) and allograft failure attributed to rejection (6.31 vs 3.99; p = 0.0023). However, African-Americans and Hispanic-Americans had similar mortality rates (2.71 vs 2.31; p = 0.4269). Conclusions African-Americans compared to Hispanic-Americans with lupus had lower kidney allograft survival when recognized risk factors of rejection were matched between groups.

HLA Mismatching Strategies for Solid Organ Transplantation - A Balancing Act

HLA matching provides numerous benefits in organ transplantation including better graft function, fewer rejection episodes, longer graft survival, and the possibility of reduced immunosuppression. Mismatches are attended by more frequent rejection episodes that require increased immunosuppression that, in turn, can increase the risk of infection and malignancy. HLA mismatches also incur the risk of sensitization, which can reduce the opportunity and increase waiting time for a subsequent transplant. However, other factors such as donor age, donor type, and immunosuppression protocol, can affect the benefit derived from matching. Furthermore, finding a well-matched donor may not be possible for all patients and usually prolongs waiting time. Strategies to optimize transplantation for patients without a well-matched donor should take into account the immunologic barrier represented by different mismatches: what are the least immunogenic mismatches considering the patient’s HLA phenotype; should repeated mismatches be avoided; is the patient sensitized to HLA and, if so, what are the strengths of the patient’s antibodies? This information can then be used to define the HLA type of an immunologically optimal donor and the probability of such a donor occurring. A probability that is considered to be too low may require expanding the donor population through paired donation or modifying what is acceptable, which may require employing treatment to overcome immunologic barriers such as increased immunosuppression or desensitization. Thus, transplantation must strike a balance between the risk associated with waiting for the optimal donor and the risk associated with a less than optimal donor.

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.

Racial differences in graft survival: a report from the North American Pediatric Renal Trials and Collaborative Studies (NAPRTCS)

Multiple studies have documented racial differences in graft survival in kidney transplant recipients. Although several studies in adult kidney transplant recipients have evaluated risk factors that might predispose to these differences, studies in pediatric patients are lacking. This study retrospectively analyzed data from the North American Pediatric Renal Trials and Collaborative Studies (NAPRTCS) to identify racial differences in kidney transplant outcomes and evaluate factors that might contribute to those differences. The study was restricted to the first NAPRTCS registry-reported kidney transplant for pediatric patients (age < or =21 yr) whose race was reported as either black or white. Univariate graft survival analyses were performed using the log rank statistic. Relative hazard rates for the effect of race on graft failure were determined using proportional hazards models. Multivariate analyses were restricted to patients with >30 d of graft survival and were adjusted for initial diagnosis, donor source, presence of delayed graft function, era of transplantation, estimated GFR at 30 d after transplantation, and number of days hospitalized in the first month after transplantation. Graft survival was significantly lower in black transplant recipients at 3 yr (70.9 versus 83.3%) and 5 yr (59.9 versus 77.7%). After controlling for confounding factors, black recipients continued to have a higher risk for graft failure than white recipients (adjusted hazard rate 1.65; 95% confidence interval 1.46 to 1.86). Significant racial differences in kidney transplant outcomes exist among pediatric patients even after controlling for confounding factors.

Revisiting survival differences by race and ethnicity among hemodialysis patients: the Dialysis Outcomes and Practice Patterns Study

Hemodialysis (HD) patients who are identified as belonging to racial or ethnic minority groups have longer survival than non-Hispanic white HD patients. This study sought to determine to what extent this survival difference is explained by comprehensive adjustment for measurable case-mix and treatment characteristics. A cohort analysis was conducted among 6677 patients between 1996 and 2001 in the American arm of the first phase of the Dialysis Outcomes and Practice Patterns Study, a prospective observational study. Using multivariable proportional hazards analysis, all-cause mortality by racial/ethnic category was compared before and after adjustment for other patient-level variables that are associated with mortality. Factors that influence the statistical associations of race/ethnicity with mortality were explored. The statistically significant (P < 0.001) associations of racial/ethnic minority categories with lower mortality in unadjusted analyses were attenuated or lost in the multivariable model. Compared with non-Hispanic white patients, the adjusted hazard ratio (HR) (95% confidence interval [CI]) for mortality was 0.86 (0.72 to 1.03) for Hispanic patients; among non-Hispanic patients, the HR (95% CI) were 0.97 (0.85 to 1.11) for black patients, 0.82 (0.56 to 1.20) for Asian patients, 0.95 (0.52 to 1.73) for Native American patients, and 0.95 (0.60 to 1.50) for patients of other races (overall P = 0.66). The survival advantages for racial/ethnic minority categories were explained most notably by the combined influence of unbalanced distributions of numerous demographic, morbidity, nutritional, and laboratory variables. The associations of race/ethnicity with survival varied little by duration of ESRD and were not influenced substantially by different rates of kidney transplantation among patients who were on HD. The survival advantages for racial and ethnic minority groups on HD are explained largely by measurable case-mix and treatment characteristics. Individual racial minority group or Hispanic patients should not be expected to survive longer on HD than non-Hispanic white patients with similar clinical attributes.

Composite Vascularized Skin/Bone Transplantation Models for Bone Marrow-Based Tolerance Studies

There is an ongoing need to understand the mechanisms of bone marrow-based allograft tolerance. This is important in clarifying the diverse variables influencing the ultimate outcome of the solid organ and composite tissue transplants. To establish bone marrow transplantation as a routine clinical application, further experimental studies should be conducted to overcome the obstacles related to the bone marrow transplantation. These obstacles include graft versus host disease, immunocompetence, and toxicity of the conditioning regimens. For these purposes, novel experimental models are needed. In an attempt to provide a reliable research tool for bone marrow-based tolerance induction studies, we introduced different experimental models of modified vascularized skin/bone marrow (VSBM) transplantation technique for tolerance induction, monitoring, and maintenance studies. In this skin/bone transplantation model, the technical feasibility of concurrent or consecutive transplantation of the combination of bilateral vascularized skin, vascularized bone marrow, or vascularized skin/bone marrow transplants was investigated. Isograft transplantations were performed between genetically identical Lewis (LEW, RT1) rats. Five different experimental designs in 5 groups of 5 animals each were studied. Group I: Bilateral vascularized skin (VS) transplantation; group II: bilateral vascularized skin/bone transplantation; group III: vascularized skin transplantation on one side and vascularized skin/bone transplantation on the contralateral side; group IV: vascularized bone transplantation on one side and vascularized skin/bone transplantation on the contralateral side; group V: vascularized bone transplantation on one side and vascularized skin transplantation on the contralateral side. Successful transplantations were performed in all groups. The survival of the isograft transplants was evaluated clinically and histologically. All skin flaps remained pink and pliable and grew new hair. The viability of the compact bone, bone marrow and skin at 100 days posttransplant was confirmed by histologic evaluation, and bone marrow revealed active hematopoiesis. Bilateral skin/bone transplantation model may serve as an experimental tool to study new strategies in tolerance induction by altering the amount of the immunogenic load in the form of skin transplant and bone marrow delivery in the vascularized form, allowing for expedited engraftment of stem and progenitor cells.

Assessing the relative risk of cardiovascular disease among renal transplant patients receiving tacrolimus or cyclosporine

Calcineurin inhibitors potentially contribute to risk of cardiovascular events through the development of new-onset diabetes mellitus, hypertension and hyperlipidemia. The exact extent to which calcineurin inhibitors affect these risk factors is difficult to establish since pre-existing renal disease and concomitant immunosuppressive agents (such as steroids or TOR inhibitors) also exert an effect. Clinical trials have consistently shown a higher incidence of new-onset diabetes mellitus with tacrolimus, which has been borne out in large-scale registry analyses. However, the risk of hypertension is approximately 5% higher with cyclosporine than tacrolimus, as is the risk of hyperlipidemia. Statin therapy is effective in treating dyslipidemia and has significant benefits in renal transplant patients. An individualized approach to choice of calcineurin inhibitor, by which cyclosporine or tacrolimus are selected based on the patient's particular risk profile, may thus help to reduce the toll of cardiovascular mortality among renal transplant recipients in the future.

The differential effect of race among pediatric kidney transplant recipients with focal segmental glomerulosclerosis

BACKGROUND

Given the differential effect of race on focal segmental glomerulosclerosis (FSGS) progression in native kidneys, recurrence of FSGS in the transplanted kidney, and allograft source, the authors conducted this study to evaluate the influence of FSGS by race and allograft source.

METHODS

Data from 8,065 pediatric renal transplant recipients (n = 620 FSGS) between 1987 and 1997 from the United Network for Organ Sharing registry were used for this study. Stratified analysis by race and allograft source allowed independent assessment of the effect of FSGS on transplant survival.

RESULTS

Among black children, allograft survival was not different between FSGS and non-FSGS patients adjusted for recipient age, recurrent disease, allograft source, zero antigen mismatch, and acute rejection (hazard ratio [HR], 1.15; 95% confidence interval [95% CI], 0.93 to 1.42; P = 0.22). Among nonblack children, the risk of allograft failure in children with FSGS was 1.31 times higher than other causes of end-stage renal disease (ESRD) in multivariate analysis (95% CI, 1.04 to 1.64; P = 0.02). Despite the impact of disease recurrence in the nonblack children with FSGS, the risk of graft failure was less for living donor recipients (HR, 1.51; 95% CI, 1.08 to 2.10) than for cadaveric recipients (HR, 1.80; 95% CI, 1.32 to 2.44) compared with the lowest risk group (nonblack, non-FSGS, living donor).

CONCLUSION

The effect of FSGS on renal allograft survival in children differs between racial groups. Children of nonblack races with FSGS have a worse allograft survival rate compared with other causes of ESRD. Within nonblack children with FSGS, living donor transplants convey a better allograft survival than cadaveric transplants.

Effect of cyclosporin pharmacokinetics on renal allograft outcome in African-Americans

African-Americans (A-As) experience inferior outcome after transplantation compared with other ethnic groups. Bioavailability of cyclosporin (CsA) has been implicated as a possible contributing factor. This paper describes the outcome of 32 A-A recipients of de novo renal allograft who received CsA-based triple immunotherapy according to individual pharmacokinetic profiles. Patients received CsA-microemulsion q 12 h, dosed initially at 3.5 mg/kg (8 am) and 3.0 mg/kg (8 pm). The am and pm doses were independently adjusted to achieve a 12-h area under the concentration-time curve (AUC0-12) of 6600-7200 nghr/mL and morning trough level (C0) of 250-325 ng/mL, respectively. Mean age was 43 +/- 12 yr, 37% (12) female. Mean AUC0-12 in 1 wk, 1, 3, 6, and 12 months were 7810 +/- 1880 nghr/mL, 9057 +/- 2097 nghr/mL, 7674 +/- 1912 nghr/mL, 7132 +/- 2040 nghr/mL, and 6503 +/- 1410 ngl/h with corresponding C0 of 301 +/- 79 ng/mL, 316 +/- 66 ng/mL, 275 +/- 59 ng/mL, 273 +/- 66 ng/mL, and 224 +/- 49 ng/mL, respectively. Acute rejection occurred in two patients (6%) 1 yr after transplantation. Prospective use of CsA pharmocokinetic profiles improves renal allograft outcome in A-As.