The relative risk of overall graft loss and acute rejection among African American renal transplant recipients is attenuated with advancing age

Trends in Disparities in Preemptive Kidney Transplantation in the United States

BACKGROUND AND OBJECTIVES

Long wait times for deceased donor kidneys and low rates of preemptive wait-listing have limited preemptive transplantation in the United States. We aimed to assess trends in preemptive deceased donor transplantation with the introduction of the new Kidney Allocation System (KAS) in 2014 and identify whether key disparities in preemptive transplantation have changed.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

We identified adult deceased donor kidney transplant recipients in the United States from 2000 to 2018 using the Scientific Registry of Transplant Recipients. Preemptive transplantation was defined as no dialysis before transplant. Associations between recipient, donor, transplant, and policy era characteristics and preemptive transplantation were calculated using logistic regression. To test for modification by KAS policy era, an interaction term between policy era and each characteristic of interest was introduced in bivariate and adjusted models.

RESULTS

The proportion of preemptive transplants increased after implementation of KAS from 9.0% to 9.8%, with 1.10 (95% confidence interval [95% CI], 1.06 to 1.14) times higher odds of preemptive transplantation post-KAS compared with pre-KAS. Preemptive recipients were more likely to be white, older, female, more educated, hold private insurance, and have ESKD cause other than diabetes or hypertension. Policy era significantly modified the association between preemptive transplantation and race, age, insurance status, and Human Leukocyte Antigen zero-mismatch (interaction P<0.05). Medicare patients had a significantly lower odds of preemptive transplantation relative to private insurance holders (pre-KAS adjusted OR, [aOR] 0.26; [95% CI, 0.25 to 0.27], to 0.20 [95% CI, 0.18 to 0.22] post-KAS). Black and Hispanic patients experienced a similar phenomenon (aOR 0.48 [95% CI, 0.45 to 0.51] to 0.41 [95% CI, 0.37 to 0.45] and 0.43 [95% CI, 0.40 to 0.47] to 0.40 [95% CI, 0.36 to 0.46] respectively) compared with white patients.

CONCLUSIONS

Although the proportion of deceased donor kidney transplants performed preemptively increased slightly after KAS, disparities in preemptive kidney transplantation persisted after the 2014 KAS policy changes and were exacerbated for racial minorities and Medicare patients.

K121Q polymorphism in the Ectonucleotide Pyrophosphatase/Phosphodiesterase 1 gene is associated with acute kidney rejection

The identification of risk factors for acute rejection (AR) may lead to strategies to improve success of kidney transplantation. Ectonucleotidases are ectoenzymes that hydrolyze extracellular nucleotides into nucleosides, modulating the purinergic signaling. Some members of the Ectonucleotidase family have been linked to transplant rejection processes. However, the association of Ectonucleotide Pyrophosphatase / Phosphodiesterase 1 (ENPP1) with AR has not yet been evaluated. The aim of this study was to evaluate the association between the K121Q polymorphism of ENPP1 gene and AR in kidney transplant patients. We analyzed 449 subjects without AR and 98 with AR from a retrospective cohort of kidney transplant patients from Southern Brazil. K121Q polymorphism was genotyped using allelic discrimination-real-time PCR. Cox regression analysis was used to evaluate freedom of AR in kidney transplant patients according to genotypes. Q allele frequency was 17.6% in recipients without AR and 21.9% in those with AR (P = 0.209). Genotype frequencies of the K121Q polymorphism were in Hardy-Weinberg equilibrium in non-AR patients (P = 0.70). The Q/Q genotype (recessive model) was associated with AR (HR = 2.83, 95% CI 1.08–7.45; P = 0.034) after adjusting for confounders factors. Our findings suggest a novel association between the ENPP1 121Q/Q genotype and AR in kidney transplant recipients.

Alemtuzumab Induction Is Associated With Equalization of Graft Outcomes Between Elderly and Nonelderly Kidney Transplant Recipients: A Single-Center Report

OBJECTIVES

Alemtuzumab (monoclonal anti-CD52 antibody) provides profound lymphocyte depletion and offers numerous advantages as an induction agent. Elderly recipients (> 65 years old) traditionally have inferior posttransplant outcomes versus younger recipients. We investigated short-term and long-term patient and graft survival rates following alemtuzumab induction in elderly recipients.

MATERIALS AND METHODS

This retrospective analysis, which included 676 renal allograft transplant recipients with alemtuzumab induction, was conducted at the University of Toledo Medical Center between March 2006 and November 2015. We used 2-sided t test, Pearson chi-square test, Fisher exact test, and Cox proportional hazard regressions with 95% confidence interval for analyses. P < .05 was significant.

RESULTS

Elderly recipients were more likely to receive a kidney from an inferior donor (deceased donor: 82% vs 72.4%; P = .030) and have higher mean kidney donor profile index (46.2 vs 38.4; P = .024) than nonelderly recipients. Elderly recipients were more likely to experience delayed graft function (15.1% vs 8.5%; P = .038). Elderly recipients demonstrated death-censored graft survival (1 year: 95.4% vs 93.1%; 3 years: 88.5% vs 93.3%; 5 years: 83.1% vs 86.4%) and rejection rates (1 year: 19.8% vs 21.2%; 3 years: 22.1% vs 25.3%; 5 years: 23.8% vs 26.9%) similar to nonelderly recipients. Elderly recipients had significantly higher overall mortality rates than recipients under 65 years old (29.8% vs. 13.2%; P = .001). Although 1-year patient survival was similar to younger recipients (94.8% vs 96.3%; P = .431), 3-year (80.0% vs 91.5%; P = .006) and 5-year (72.9% vs 86.2%; P = .19) rates were significantly decreased in elderly recipients.

CONCLUSIONS

Elderly age is not a predictor of rejection or death-censored graft loss in individuals who receive alemtuzumab induction. Despite elevated overall mortality, elderly recipients induced with alemtuzumab demonstrated rejection, graft, and short-term patient survival rates similar to younger recipients.

Alemtuzumab Induction Is Associated With an Equalization of Outcomes Between White and African American Kidney Transplant Recipients

OBJECTIVES

Our aim was to assess outcomes in White and African American kidney transplant recipients after induction with alemtuzumab.

MATERIALS AND METHODS

We performed a retrospective study of 464 patients who received deceased-donor kidney transplants and were induced with alem-tuzumab between March 2006 and May 2015. We evaluated ethnic influences on patient and graft survival, delayed graft function, allograft failure, and rejection.

RESULTS

There were 337 White (67.3%) and 127 African American (25.3%) patients. We observed no significant differences in 1-, 3-, 5-, and 7- year death-censored graft survival. We also observed no significant differences in 1-, 3-, and 5-year patient survival rates. Having African American ethnicity was not a significant predictor of rejection, graft survival, or patient survival.

CONCLUSIONS

Our results indicate that recipient ethnicity is not a predictor of rejection, graft survival, or patient survival. White and African American kidney transplant recipients induced with alemtuzumab experienced an equalization of outcomes.

Cytolytic Induction Therapy Improves Clinical Outcomes in African-American Kidney Transplant Recipients

OBJECTIVE

Determine the impact of cytolytic versus IL-2 receptor antibody (IL-2RA) induction on acute rejection, graft loss and death in African-American (AA) kidney transplant (KTX) recipients.

BACKGROUND

AAs are underrepresented in clinical trials in transplantation; thus, there is controversy regarding the optimal choice of perioperative antibody induction in KTX to improve outcomes.

METHODS

National cohort study using US transplant registry data from January 1, 2000 to December 31, 2009 in adult solitary AA KTX recipients, with at least 5 years of follow-up. Multivariable logistic and Cox regression were utilized to assess the outcomes of acute rejection, graft loss, and mortality, with interaction terms to assess effect modification.

RESULTS

Twenty-five thousand eighty-four adult AAs receiving solitary KTX were included, 16,927 (67.5%) received cytolytic induction and 8157 (32.5%) received IL-2RA induction. After adjustment for recipient sociodemographics, donor, and transplant characteristics, the use of cytolytic induction therapy reduced the risk of acute rejection by 32% (OR 0.68, 0.62-0.75), graft loss by 9% (HR 0.91, 0.86-0.97), and death by 12% (HR 0.88, 0.83-0.94). There were a number of significant effect modifiers, including public insurance, panel reactive antibody, delayed graft function, and steroid withdrawal; in these groups, cytolytic induction substantially improved clinical outcomes.

CONCLUSIONS

These data demonstrate that cytolytic induction therapy, as compared with IL-2RA, reduces the risk of rejection, graft loss, and death in adult AA KTX recipients, particularly in those who are sensitized, receive public insurance, develop delayed graft function, or undergo steroid withdrawal.

Overall Graft Loss Versus Death-Censored Graft Loss: Unmasking the Magnitude of Racial Disparities in Outcomes Among US Kidney Transplant Recipients

BACKGROUND

Black kidney transplant recipients experience disproportionately high rates of graft loss. This disparity has persisted for 40 years, and improvements may be impeded based on the current public reporting of overall graft loss by US regulatory organizations for transplantation.

METHODS

Longitudinal cohort study of kidney transplant recipients using a data set created by linking Veterans Affairs and US Renal Data System information, including 4918 veterans transplanted between January 2001 and December 2007, with follow-up through December 2010. Multivariable analysis was conducted using 2-stage joint modeling of random and fixed effects of longitudinal data (linear mixed model) with time to event outcomes (Cox regression).

RESULTS

Three thousand three hundred six non-Hispanic whites (67%) were compared with 1612 non-Hispanic black (33%) recipients with 6.0 ± 2.2 years of follow-up. In the unadjusted analysis, black recipients were significantly more likely to have overall graft loss (hazard ratio [HR], 1.19; 95% confidence interval [95% CI], 1.07-1.33), death-censored graft loss (HR, 1.67; 95% CI, 1.45-1.92), and lower mortality (HR, 0.83; 95% CI, 0.72-0.96). In fully adjusted models, only death-censored graft loss remained significant (HR, 1.38; 95% CI, 1.12-1.71; overall graft loss [HR, 1.08; 95% CI, 0.91-1.28]; mortality [HR, 0.84; 95% CI, 0.67-1.06]). A composite definition of graft loss reduced the magnitude of disparities in blacks by 22%.

CONCLUSIONS

Non-Hispanic black kidney transplant recipients experience a substantial disparity in graft loss, but not mortality. This study of US data provides evidence to suggest that researchers should focus on using death-censored graft loss as the primary outcome of interest to facilitate a better understanding of racial disparities in kidney transplantation.

Profiling risk for acute rejection in kidney transplantation: recipient age is a robust risk factor

Careful management of immunosuppression is paramount to prevent acute rejection in kidney transplantation. We studied a cohort of 139,875 kidney transplant recipients from the Organ Procurement and Transplantation Network (OPTN) database between 2002 and 2013. We confirmed the analysis with a cohort of 35,277 who received thymoglobulin induction with tacrolimus maintenance, and a third cohort of 12,161 recipients who received basiliximab induction with tacrolimus maintenance. We performed multivariate logistic regression analyses on data from all three cohorts and identified independent risk factors for treated acute rejection at 1 year. Recipient age was a robust risk factor for rejection in all three cohorts in a dose response pattern. Young age (18-25 years) was among the strongest risk factors for rejection in all three cohorts; thymoglobulin cohort: OR 1.87 (1.59-2.19); basiliximab cohort: OR 2.41 (1.89-3.05); and inclusive cohort: OR 1.97 (1.83-2.12). The opposite was true for old age (65-69 years); thymoglobulin cohort: OR 0.69 (0.59-0.81); basiliximab cohort: OR 0.77 (0.62-0.96); and inclusive cohort: OR 0.75 (0.70-0.80). This study is unique because it is the largest and most comprehensive multivariate analysis that demonstrates recipient age is a robust risk factor for acute rejection in an inverse dose response pattern.

Variation in Cost and Quality in Kidney Transplantation

BACKGROUND

Bending the cost curve in medical expenses is a high national priority. The relationship between cost and kidney allograft failure has not been fully investigated in the United States.

METHODS

Using Medicare claims from the United States Renal Data System, we determined costs for all adults with Medicare coverage who underwent kidney transplant January 1, 2007, to June 30, 2009. We compared relative cost (observed/expected payment) for year 1 after transplantation for all transplant centers, adjusting for recipient, donor, and transplant characteristics, region, and local wage index. Using program-specific reports from the Scientific Registry of Transplant Recipients, we correlated relative cost with observed/expected allograft failure between centers, excluding small centers.

RESULTS

Among 19,603 transplants at 166 centers, mean observed cost per patient per center was $65,366 (interquartile range, $55,094-$71,624). Mean relative cost was 0.99 (± 0.20); mean observed/expected allograft failure was 1.03 (± 0.46). Overall, there was no correlation between relative cost and observed/expected allograft failure (r = 0.096, P = 0.22). Comparing centers with higher than expected costs and allograft failure rates (lower performing) and centers with lower than expected costs and failure rates (higher-performing) showed differences in donor and recipient characteristics. As these characteristics were accounted for in the adjusted cost and allograft failure models, they are unlikely to explain the differences between higher- and lower-performing centers.

CONCLUSIONS

Further investigations are needed to determine specific cost-effective practices of higher- and lower-performing centers to reduce costs and incidence of allograft failure.

Impact of Maintenance Steroids versus Rapid Steroid Withdrawal in African-American Kidney Transplant Recipients: Comparison of Two Urban Centers

Background

Rapid steroid withdrawal (RSW) is used increasingly in kidney transplantation but long-term outcomes in African-American (AA) recipients are not well known. We compared 1 and 5 year transplant outcomes in a large cohort of AA patients who were maintained on continued steroid therapy (CST) to those who underwent RSW.

Methods

Post-transplant courses of A as receiving kidney allografts from 2003–2011 at two urban transplant centers in Chicago were followed. Prior to outcome analysis, we used Inverse Probability of Treatment Weights (IPTW) to match the two groups on a set of baseline risk factors. Graft and patient survival, GFR at 1 and 5 years, incidence and type of rejection, incidence of post-transplant diabetes mellitus (PTDM), delayed graft function, CMV and BK viremia were compared.

Results

There were 150 AA recipients in the CST analytic group and 157 in the RSW analytic group. Graft and patient survival was similar between the two groups. Rates of CMV viremia were higher in the RSW compared to the CST analytic group at 1 year. Biopsy-proven acute rejection and PTDM were similar between the RSW and CST groups.

Conclusions

In AA recipients, RSW has similar long-term outcomes to CST.

An analysis of pancreas transplantation outcomes based on age groupings--an update of the UNOS database

INTRODUCTION

Previously, increasing age has been a part of the exclusion criteria used when determining eligibility for a pancreas transplant. However, the analysis of pancreas transplantation outcomes based on age groupings has largely been based on single-center reports.

METHODS

A UNOS database review of all adult pancreas and kidney-pancreas transplants between 1996 and 2012 was performed. Patients were divided into groups based on age categories: 18-29 (n = 1823), 30-39 (n = 7624), 40-49 (n = 7967), 50-59 (n = 3160), and ≥60 (n = 280). We compared survival outcomes and demographic variables between each age grouping.

RESULTS

Of the 20 854 pancreas transplants, 3440 of the recipients were 50 yr of age or above. Graft survival was consistently the greatest in adults 40-49 yr of age. Graft survival was least in adults age 18-29 at one-, three-, and five-yr intervals. At 10- and 15-yr intervals, graft survival was the poorest in adults >60 yr old. Patient survival and age were found to be inversely proportional; as the patient population's age increased, survival decreased.

CONCLUSION

Pancreas transplants performed in patients of increasing age demonstrate decreased patient and graft survival when compared to pancreas transplants in patients <50 yr of age.

Significant racial differences in the key factors associated with early graft loss in kidney transplant recipients

BACKGROUND

There is continued and significant debate regarding the salient etiologies associated with graft loss and racial disparities in kidney transplant recipients.

METHODS

This was a longitudinal cohort study of all adult kidney transplant recipients, comparing patients with early graft loss (<5 years) to those with graft longevity (surviving graft with at least 5 years of follow-up) across racial cohorts [African-American (AA) and non-AA] to discern risk factors.

RESULTS

524 patients were included, 55% AA, 151 with early graft loss (29%) and 373 with graft longevity (71%). Consistent within both races, early graft loss was significantly associated with disability income [adjusted odds ratio (AOR) 2.2, 95% CI 1.1-4.5], Kidney Donor Risk Index (AOR 3.2, 1.4-7.5), rehospitalization (AOR 2.1, 1.0-4.4) and acute rejection (AOR 4.4, 1.7-11.6). Unique risk factors in AAs included Medicare-only insurance (AOR 8.0, 2.3-28) and BK infection (AOR 5.6, 1.3-25). Unique protective factors in AAs included cardiovascular risk factor control: AAs with a mean systolic blood pressure <150 mm Hg had 80% lower risk of early graft loss (AOR 0.2, 0.1-0.7), while low-density lipoprotein <100 mg/dl (AOR 0.4, 0.2-0.8), triglycerides <150 mg/dl (AOR 0.4, 0.2-1.0) and hemoglobin A1C <7% (AOR 0.2, 0.1-0.6) were also protective against early graft loss in AA, but not in non-AA recipients.

CONCLUSIONS

AA recipients have a number of unique risk factors for early graft loss, suggesting that controlling cardiovascular comorbidities may be an important mechanism to reduce racial disparities in kidney transplantation.

The impact of deceased donor kidney risk significantly varies by recipient characteristics

As of May 2012, over 92 000 patients were awaiting a solitary kidney transplant in the United States and new waitlist registrations have been rising for over a decade. The decreasing availability of donor organs makes it imperative that organ allocation be as efficient and effective as possible. We performed a retrospective cohort study of adult recipients in the United States (n=109 392) using Scientific Registry of Transplant Recipients data. The primary aim was to evaluate the interaction of donor risk with recipient characteristics on posttransplant outcomes. Donor quality (based on kidney donor risk index [KDRI]) had significant interactions by race, primary diagnosis and age. The hazard of KDRI on overall graft loss in non-African Americans was 2.16 (95%CI 2.08-2.25) versus 1.85 (95%CI 1.75-1.95) in African Americans (p<0.0001), 2.16 (95%CI 2.08-2.24) in nondiabetics versus 1.84 (95%CI 1.74-1.94) in diabetics (p<0.0001), and 2.22 (95%CI 2.13-2.32) in recipients<60 years versus 1.83 (95%CI 1.74-1.92) in recipients≥60 (p<0.0001). The relative hazard for diabetics at KDRI=0.5 was 1.49 but at KDRI=2.0 the hazard was significantly attenuated to 1.17; among African Americans the respective risks were 1.50 and 1.17 and among recipients 60 and over, it was between 1.64 and 1.22. These findings are critical considerations for informed decision-making for transplant candidates.

Association of race and age with survival among patients undergoing dialysis

CONTEXT

Many studies have reported that black individuals undergoing dialysis survive longer than those who are white. This observation is paradoxical given racial disparities in access to and quality of care, and is inconsistent with observed lower survival among black patients with chronic kidney disease. We hypothesized that age and the competing risk of transplantation modify survival differences by race.

OBJECTIVE

To estimate death among dialysis patients by race, accounting for age as an effect modifier and kidney transplantation as a competing risk.

DESIGN, SETTING, AND PARTICIPANTS

An observational cohort study of 1,330,007 incident end-stage renal disease patients as captured in the United States Renal Data System between January 1, 1995, and September 28, 2009 (median potential follow-up time, 6.7 years; range, 1 day-14.8 years). Multivariate age-stratified Cox proportional hazards and competing risk models were constructed to examine death in patients who receive dialysis.

MAIN OUTCOME MEASURES

Death in black vs white patients who receive dialysis.

RESULTS

Similar to previous studies, black patients undergoing dialysis had a lower death rate compared with white patients (232,361 deaths [57.1% mortality] vs 585,792 deaths [63.5% mortality], respectively; adjusted hazard ratio [aHR], 0.84; 95% confidence interval [CI], 0.83-0.84; P <.001). However, when stratifying by age and treating kidney transplantation as a competing risk, black patients had significantly higher mortality than their white counterparts at ages 18 to 30 years (27.6% mortality vs 14.2%; aHR, 1.93; 95% CI, 1.84-2.03), 31 to 40 years (37.4% mortality vs 26.8%; aHR, 1.46; 95% CI, 1.41-1.50), and 41 to 50 years (44.8% mortality vs 38.0%; aHR, 1.12; 95% CI, 1.10-1.14; P <.001 for interaction terms between race and each aforementioned age category), as opposed to patients aged 51 to 60 years (51.5% vs 50.9%; aHR, 0.93; 95% CI, 0.92-0.94), 61 to 70 years (64.9% vs 67.2%; aHR, 0.87; 95% CI, 0.86-0.88), 71 to 80 years (76.1% vs 79.7%; aHR, 0.85; 95% CI, 0.84-0.86), and older than 80 years (82.4% vs 83.6%; aHR, 0.87; 95% CI, 0.85-0.88).

CONCLUSIONS

Overall, among dialysis patients in the United States, there was a lower risk of death for black patients compared with their white counterparts. However, the commonly cited survival advantage for black dialysis patients applies only to older adults, and those younger than 50 years have a higher risk of death.