Relative impact of donor type on renal allograft survival in black and white recipients

Longevity Matching for Living Donor Renal Transplantation

INTRODUCTION

This study identifies the effect of individual donor and recipient characteristics on graft survival in living-donor kidney transplantation (LDKT) using a recently described novel measure, kidney life years (KLYs).

MATERIALS AND METHODS

The Organ Procurement and Transplantation Network/United Network for Organ Sharing database was used to identify first-time kidney-only LDKT recipients between 1987 and 2020 who did not experience death with a functioning graft (DWFG) and were not missing relevant information (n = 87,290). Patient characteristics were evaluated using Cox and multiple regression analyses, with the dependent variable being KLYs. An equation for expected KLYs based on patient characteristics was created using regression coefficients. The equation was validated using bootstrapped Pearson correlations and then applied to the DWFG group for comparison.

RESULTS

Based on statistical significance from Cox and multiple linear regression analyses, 9 of the original 18 variables were selected for inclusion in the equation. Variables with notable impact included HLA match points (0.021 KLYs; 95% CI: [0.019,0.024]; P ≤ .001), Donor Age (-0.030 KLYs; 95% CI: [-0.035,-0.025]; P ≤ .001), and Donor African American Ethnicity (-2.356 KLYs; 95% CI: [-2.552,-2.159]; P ≤ .001). Equation validation was supported, given a negative correlation (r = -0.071; P ≤ .001) between expected KLY change and observed graft failure. Expected KLY change was found to be greater in those who eventually DWFG when compared with all other LDKTs (t = -5.735, P ≤ .001).

CONCLUSIONS

Increasing HLA match points may be more beneficial for graft longevity than minimizing donor age in comparisons using realistic between-donor differences. Additionally, greater average expected KLYs in those who ultimately DWFG may illustrate an opportunity for improved donor-recipient matching.

Clinicians' attitudes and approaches to evaluating the potential living kidney donor-recipient relationship: An interview study

AIM

Careful assessment of the potential donor-recipient relationship is recommended by guidelines to prevent undue coercion, and to ensure realistic expectations and genuine motivations. However, relationships are complex, nuanced and value-laden, and can be challenging to evaluate in living kidney donation. We aimed to describe the attitudes and approaches of transplant clinicians towards assessing the relationship between potential living kidney donors and their recipients.

METHODS

Semi-structured interviews were conducted with 54 transplant clinicians (nephrologists, surgeons, coordinators, social workers, psychiatrists and psychologists) from 32 transplant centres across nine countries including Australia, United States, Canada and New Zealand. Transcripts were analyzed thematically.

RESULTS

Four themes were identified: protecting against vulnerability and premature decisions (ensuring genuine motivation, uncovering precarious dynamics and pre-empting conflict, shared accountability, relying on specialty psychosocial expertise, trusting intimate bonds, tempering emotional impulsivity); safeguarding against coercion (discerning power imbalance, justified inquiry, awareness of impression management); minimizing potential threat to relationships (preserving the bond, giving equitable attention to donors and recipients, ensuring realistic expectations); and ambiguities in making judgments (adjudicating appropriateness and authenticity of relationships, questioning professional intervening, uncertainties in subjective and emotional assessments).

CONCLUSIONS

Clinicians felt ethically compelled to minimize the risk of undue coercion and to protect donors and recipients when evaluating the donor-recipient relationship. However, disentangling voluntariness and altruism from potential undisclosed pressures to enact societal and family duty, making decisions within this complex, multi-stakeholder context, and avoiding the imposition of undue paternalism and donor autonomy, were challenging. Multidisciplinary expertise and practical strategies for managing uncertainties are required.

A comparative analysis of survival of patients on dialysis and after kidney transplantation

Background

Kidney transplant survival benefits are not observed for around 8 months after transplantation because of a higher complications rate in early post-transplant periods. This study compares survival of patients awaiting transplantation with survival of transplant recipients and non-listed dialysis patients in Ireland.

Methods

In this retrospective analysis, the relative-risk (RR) of death was assessed with time-dependent, non-proportional hazards analysis, with adjustment for age, cause of end-stage kidney disease (ESKD), time from first treatment for ESKD to placement on the waiting list and year of initial placement on the list.

Results

A total of 3597 patients were included. Annual death rates per 100 patient-years at risk for all patients on dialysis, waiting-list patients and transplant recipients were 16.5, 2.4 and 1.2, respectively. Death rate was highest among diabetics. The relative risk of death for all patients on dialysis was five times higher than the waiting-list patients [RR, 4.90; 95% confidence interval (CI), 3.70–6.52; P < 0.001]. Time to survival equilibration was 1 year. Thereafter, the 5-year mortality risk was estimated to be 47% lower than that of the patients on the waiting list (RR, 0.53; 95% CI, 0.37–0.77; P = 0.001).

Conclusions

Transplant recipients had a higher risk of death initially, but a better long-term survival. Time to death risk equilibration was longer compared with other studies. This could be explained by better survival rates in our waiting-list cohort.

Variation in Access to Kidney Transplantation Across Renal Programs in Ontario, Canada

In the United States, kidney transplant rates vary significantly across end-stage renal disease (ESRD) networks. We conducted a population-based cohort study to determine whether there was variability in kidney transplant rates across renal programs in a health care system distinct from the United States. We included incident chronic dialysis patients in Ontario, Canada, from 2003 to 2013 and determined the 1-, 5-, and 10-year cumulative incidence of kidney transplantation in 27 regional renal programs (similar to U.S. ESRD networks). We also assessed the cumulative incidence of kidney transplant for "healthy" dialysis patients (aged 18-50 years without diabetes, coronary disease, or malignancy). We calculated standardized transplant ratios (STRs) using a Cox proportional hazards model, adjusting for patient characteristics (maximum possible follow-up of 11 years). Among 23 022 chronic dialysis patients, the 10-year cumulative incidence of kidney transplantation ranged from 7.4% (95% confidence interval [CI] 4.8-10.7%) to 31.4% (95% CI 16.5-47.5%) across renal programs. Similar variability was observed in our healthy cohort. STRs ranged from 0.3 (95% CI 0.2-0.5) to 1.5 (95% CI 1.4-1.7) across renal programs. There was significant variation in kidney transplant rates across Ontario renal programs despite patients having access to the same publicly funded health care system.

Protocol of the KTFT-TALK study to reduce racial disparities in kidney transplant evaluation and living donor kidney transplantation

Living donor kidney transplantation (LDKT) is the optimal treatment for end-stage kidney disease (ESKD). The evaluation process for a kidney transplant is complex, time consuming, and burdensome to the ESKD patient. Also, race disparities exist in rates of transplant evaluation completion, transplantation, and LDKT. In December 2012 our transplant center implemented a streamlined, one-day evaluation process, dubbed Kidney Transplant Fast Track (KTFT). This paper describes the protocol of a two-part study to evaluate the effectiveness of KTFT at increasing transplant rates (compared to historical controls) and the TALK intervention (Talking About Live Kidney Donation) at increasing LDKT during KTFT. All participants will receive the KTFT evaluation as part of their usual care. Participants will be randomly assigned to TALK versus no-TALK conditions. Patients will undergo interviews at pre-transplant work-up and transplant evaluation. Transplant status will be tracked via medical records. Our aims are to: (1) test the efficacy and cost effectiveness of the KTFT in reducing time to complete kidney transplant evaluation, and increasing kidney transplant rates relative to standard evaluation practices; (2) test whether TALK increases rates of LDKT during KTFT; and (3) determine whether engaging in a streamlined and coordinated-care evaluation experience within the transplant center reduces negative perceptions of the healthcare system. The results of this two-pronged approach will help pave the way for other transplant centers to implement a fast-track system at their sites, improve quality of care by transplanting a larger number of vulnerable patients, and address stark race/ethnic disparities in rates of LDKT.

Sensitization trends after renal allograft failure: the role of DQ eplet mismatches in becoming highly sensitized

Sensitization following renal allograft failure (AF) is highly variable. Some patients remain non-sensitized (NS), while others become highly sensitized (HS). We studied 66 NS patients who experienced AF after initial kidney transplantation. Post-failure, two main groups of NS panel reactive antibody (PRA) class I and II <10% and HS patients (PRA class I or II ≥80%) were identified. The impact of acute rejection (AR), immunosuppression withdrawal (ISW) at AF, allograft nephrectomy, graft intolerance syndrome (GIS), and both standard serologic and eplet-based mismatches (MM) in inducing HS status after failure was examined. Late PRA testing post-failure revealed 18 patients remained NS and 34 patients became HS. African American recipients, ISW at AF, DQB1 eplet MM, and presence of GIS were associated with becoming HS. Presence of total zero eplet MM, zero DQA1/B1 eplet MM, continuation of immunosuppression after failure, and a hyporesponsive immune status characterized by recurrent infections were features of NS patients. DQ eplet MM represents a significant risk for becoming HS after AF. Studies comparing ISW vs. continuation in re-transplant candidates with high baseline DQ eplet MM burden should be performed. This may provide insights if sensitization post-AF can be lessened.

An overview of disparities and interventions in pediatric kidney transplantation worldwide

Despite the stated goals of the transplant community and the majority of organ allocation systems, persistent racial disparities in pediatric kidney transplantation exist throughout the world. These disparities are evident in both living and deceased donor kidney transplantation and are independent of any clinical differences between racial groups. The reasons for these persistent disparities are multifactorial, reflecting both patient and provider barriers to care. In this review, we examine the most current findings regarding disparities in pediatric kidney transplantation and consider interventions which may help reduce those disparities.

Racial disparities in organ donation and why

PURPOSE OF REVIEW

High prevalence of comorbidities such as diabetes, hypertension, obesity, hepatitis B and C, in minority groups, results in racial minorities being disproportionally represented on transplant waiting lists. Organ transplantation positively impacts patient survival but greater access is limited by a severe donor shortage.

RECENT FINDINGS

Unfortunately, minority groups also suffer from disparities in deceased and living donation. African-Americans comprise 12.9% of the population and 34% of the kidney transplant waiting list but only 13.8% of deceased donors. Barriers to minority deceased donation include: decreased awareness of transplantation, religious or cultural distrust of the medical community, fear of medical abandonment and fear of racism. Furthermore, African-Americans comprise only 11.8% of living donors. Barriers to minority living donation include: unwillingness to donate, medical comorbid conditions, trust or fear of medical community, loss to follow-up, poor coping mechanisms, financial concerns, reluctance to ask family members and friends, fear of surgery, and lack of awareness about living donor kidney transplantation.

SUMMARY

Transplant center-based education classes significantly and positively impact African-American concerns and beliefs surrounding living donation. Community and national strategies utilizing culturally sensitive communication and interventions can ameliorate disparities and improve access to transplantation.

Waiting time on dialysis as the strongest modifiable risk factor for renal transplant outcomes: a paired donor kidney analysis

BACKGROUND

Waiting time on dialysis has been shown to be associated with worse outcomes after living and cadaveric transplantation. To validate and quantify end-stage renal disease (ESRD) time as an independent risk factor for kidney transplantation, we compared the outcome of paired donor kidneys, destined to patients who had ESRD more than 2 years compared to patients who had ESRD less than 6 months.

METHODS

We analyzed data available from the U.S. Renal Data System database between 1988 and 1998 by Kaplan-Meier estimates and Cox proportional hazards models to quantify the effect of ESRD time on paired cadaveric kidneys and on all cadaveric kidneys compared to living-donated kidneys.

RESULTS

Five- and 10-year unadjusted graft survival rates were significantly worse in paired kidney recipients who had undergone more than 24 months of dialysis (58% and 29%, respectively) compared to paired kidney recipients who had undergone less than 6 months of dialysis (78% and 63%, respectively; P<0.001 each). Ten-year overall adjusted graft survival for cadaveric transplants was 69% for preemptive transplants versus 39% for transplants after 24 months on dialysis. For living transplants, 10-year overall adjusted graft survival was 75% for preemptive transplants versus 49% for transplants after 24 month on dialysis.

CONCLUSIONS

ESRD time is arguably the strongest independent modifiable risk factor for renal transplant outcomes. Part of the advantage of living-donor versus cadaveric-donor transplantation may be explained by waiting time. This effect is dominant enough that a cadaveric renal transplant recipient with an ESRD time less than 6 months has the equivalent graft survival of living donor transplant recipients who wait on dialysis for more than 2 years.

Association of cytokine single nucleotide polymorphisms with B7 costimulatory molecules in kidney allograft recipients

African-American race is associated with an increased risk of allograft loss, suggesting that African-American patients may form an immunologically higher risk group. Previously, we demonstrated that immune cell costimulatory molecule expression is significantly higher in African-Americans than in Caucasians. Polymorphic variations in the genes for cytokines have been associated with a number of immunological conditions, and with transplant rejection. This study was performed to determine the distribution, in African-American and Caucasian renal transplant recipients, of single nucleotide polymorphisms (SNPs) in the following cytokine genes: tumor necrosis factor-alpha (TNF-alpha), interferon-gamma (IFN-gamma), interleukin (IL)-6, IL-10, and transforming growth factor-beta (TGF-beta). Cytokine production from blood cells was determined, and cell-surface B7 (CD80, CD86) expression was measured. There was a significant link between IL-10 genotype and acute rejection episodes, but only in African-American patients (p < 0.01). Also, African-American patients had a significantly higher probability of having the IL-6 G-allele (p < 0.0001), which is associated with a high production of IL-6 protein. Incubation of blood cells with IL-6 resulted in increased expression of surface CD80 and CD86, while IL-10 decreased CD80 expression. This study demonstrated a clear correlation of the IL-6 G-allele with increased cellular CD80 expression and the IL-10 G-allele with decreased CD80 expression. These data raise the possibility that specific genotypes are associated with local cytokine regulation of cell-surface costimulatory molecule expression. African-American patients may have a genetically determined, quantitatively different immune response than Caucasian patients, contributing to adverse transplant outcomes.

Increased costimulatory responses in African-American kidney allograft recipients

BACKGROUND

The issue of racial differences in immune responses has been seldom investigated, despite the increased incidence of transplant rejection and inferior allograft outcomes in African-Americans (AA). We previously reported significantly increased expression of costimulatory molecules on peripheral blood cells from healthy adult AA compared with Caucasian (CS) volunteers. This report extends the study to pediatric kidney allograft recipients.

METHODS

Surface antigen expression by peripheral blood mononuclear cells (MNC) from AA and CS transplant patients was determined by flow cytometry, after staining with specific antibodies. In vitro proliferation, in a one-way mixed lymphocyte response (MLR), was measured after stimulation with allogeneic irradiated mononuclear cells. The concentration of cyclosporine (CsA) achieving 50% inhibition (IC50) of in vitro proliferative responses to PHA and OKT3 was calculated.

RESULTS

MNC from AA patients were shown to have significantly higher expression of CD80 (CS 5.2% +/- 0.6, AA 9.6% +/- 1.2, P < 0.0001) than cells from CS patients. Additionally, the cells from AA transplant recipients proliferated significantly more in an MLR (stimulation index: CS 8 +/- S2, AA 25 +/- 8, P < 0.05), and the CsA IC50 values, during proliferation to PHA and OKT3, were significantly higher in AA compared to CS patients.

CONCLUSIONS

Although socioeconomic factors and therapeutic compliance are undoubtedly important issues in long-term allograft survival, our data suggest that AA patients mount more vigorous immune responses to antigens. The increased requirement for immunosuppression may be linked to racial variations in costimulatory molecule expression on antigen-presenting cells.

Elevated blood pressure predicts the risk of acute rejection in renal allograft recipients

BACKGROUND

Acute rejection (AR) is a strong predictor of renal allograft survival. Recent advances in immunosuppression have reduced considerably the incidence of AR. Still, approximately 25% of patients have AR early post-transplant, and the factors that predispose to AR have not been fully clarified.

METHODS

The study includes 1641 adults, recipients of first cadaveric (CAD, N = 1195) or living related renal grafts (LRD, N = 446), transplanted in one institution. The variables associated with the occurrence of AR during the first year post-transplant were identified.

RESULTS

By univariate analyses, AR was associated with the following variables: younger (P < 0.001); heavier (P = 0.003); and African American recipients (P = 0.002); CAD transplants (P = 0.001); higher number of HLA mismatches (P = 0.001); delayed graft function (DGF, P = 0.001); higher levels of serum creatinine post-transplant (P = 0.003); and higher levels of systolic and/or diastolic blood pressure (BP) post-transplant (P < 0.001). Higher BP levels were also associated with earlier AR episodes (P < 0.0001). By multivariable analysis AR was significantly associated with recipient age, number of HLA mismatches, DGF, pre-PRA and systolic BP. Analysis of BP measured weekly post-transplant indicated that elevated BP levels, even three weeks prior to the AR episode, were significantly associated with AR. For every level of BP, the use of BP medications was associated with a lower incidence of AR (P < 0.0001). Furthermore, the use of calcium channel blockers was also associated with lower incidence of AR (P = 0.001). Of note, 81% of recipients whose BP increased after the transplant had AR. In contrast, 22% of patients whose BP declined post-transplant had AR.

CONCLUSIONS

Elevated BP levels post-transplant identify patients at high risk of AR independently of graft function. Treatment of BP and reduction of BP levels appears to be associated with a decreased risk of AR. We hypothesize that high BP may be an indicator of a particular type of allograft damage, perhaps ischemic, that may predispose to AR.

Comparison of mortality in all patients on dialysis, patients on dialysis awaiting transplantation, and recipients of a first cadaveric transplant

BACKGROUND AND METHODS

The extent to which renal allotransplantation - as compared with long-term dialysis - improves survival among patients with end-stage renal disease is controversial, because those selected for transplantation may have a lower base-line risk of death. In an attempt to distinguish the effects of patient selection from those of transplantation itself, we conducted a longitudinal study of mortality in 228,552 patients who were receiving long-term dialysis for end-stage renal disease. Of these patients, 46,164 were placed on a waiting list for transplantation, 23,275 of whom received a first cadaveric transplant between 1991 and 1997. The relative risk of death and survival were assessed with time-dependent nonproportional-hazards analysis, with adjustment for age, race, sex, cause of end-stage renal disease, geographic region, time from first treatment for end-stage renal disease to placement on the waiting list, and year of initial placement on the list.

RESULTS

Among the various subgroups, the standardized mortality ratio for the patients on dialysis who were awaiting transplantation (annual death rate, 6.3 per 100 patient-years) was 38 to 58 percent lower than that for all patients on dialysis (annual death rate, 16.1 per 100 patient-years). The relative risk of death during the first 2 weeks after transplantation was 2.8 times as high as that for patients on dialysis who had equal lengths of follow-up since placement on the waiting list, but at 18 months the risk was much lower (relative risk, 0.32; 95 percent confidence interval, 0.30 to 0.35; P<0.001). The likelihood of survival became equal in the two groups within 5 to 673 days after transplantation in all the subgroups of patients we examined. The long-term mortality rate was 48 to 82 percent lower among transplant recipients (annual death rate, 3.8 per 100 patient-years) than patients on the waiting list, with relatively larger benefits among patients who were 20 to 39 years old, white patients, and younger patients with diabetes.

CONCLUSIONS

Among patients with end-stage renal disease, healthier patients are placed on the waiting list for transplantation, and long-term survival is better among those on the waiting list who eventually undergo transplantation.

Peripheral blood antigen-presenting cells from African-Americans exhibit increased CD80 and CD86 expression

Despite the increased incidence and severity of many autoimmune diseases and transplant rejection in African-Americans (AA) compared with Caucasians (CS), very few studies have addressed issues of racial variation during antigen presentation. This investigation was performed as a preliminary exploration of differences in peripheral blood cell costimulatory functions between healthy AA (n = 20) and CS (n = 20) subjects. The expression of surface costimulatory molecules on peripheral blood cells, mononuclear cells enriched by Ficoll density centrifugation, and plastic adherent antigen-presenting cells (APC) was determined by flow cytometry using fluorescent-labelled MoAbs. The expression of both B7 costimulatory molecules was significantly higher on the cells from AA subjects compared with cells from CS subjects (CD80, P < 0.05; CD86, P < 0.05). Also, following 18 h of culture with rhIL-1beta, there was a significant increase in the percentage of APC from AA expressing high levels of the costimulatory molecule CD80 (P < 0.05). Costimulatory function during mitogen and antigen presentation was determined by 3H-thymidine incorporation during T cell proliferation. Purified T cells from AA subjects demonstrated significantly increased proliferation to phytohaemagglutinin (PHA). The differences reported here suggest that racial variations in peripheral blood APC characteristics may exist. Given the importance of costimulation in maintaining long-term immune responses, these data suggest a further direction for the investigation of racial disparity in autoimmune disease pathology and transplant rejection rates.