Progress Made Toward Equitable Transplantation in Children and Young Adults with Kidney Disease

Abstract

Racial disparities in pediatric kidney transplantation have been well described over the last two decades and include disparities in preemptive transplantation, waitlisting, time from activation to transplantation, living donation, and graft outcomes. Changes to the organ allocation system including the institution of Share 35 in 2005 and the Kidney Allocation System (KAS) of 2014 have resulted in resolution of some, but not all racial-ethnic disparities. Despite overall improvements in time from waitlist activation to transplant, disparities remain in preemptive transplantation, time to waitlisting and living donor transplantation. Although improving under the KAS, racial disparities remain in graft survival as well. Racial disparity in kidney transplant access and graft survival is an international problem within pediatric nephrology. Although the racial group affected may differ, various minoritized pediatric groups across the world are affected by transplant disparities. Social determinants of health including financial access, language barriers and the presence of a healthy living donor play a role in mediating these disparities. Further investigation is needed to better understand and intervene upon modifiable social, biologic and cultural factors driving the remaining disparity in transplant outcomes.

Introduction

Pediatric kidney transplantation dramatically alters the quality of life and life expectancy of children with kidney failure. Because of this, it is considered the gold standard in kidney replacement therapy with a goal of minimizing the time spent on dialysis and, when possible, avoiding dialysis all together. Unfortunately, there have been historic disparities in access to this life-altering treatment and much work is needed to ensure disparate gaps are assessed and closed.

Racial-ethnic disparities in pediatric kidney transplantation manifest at varying points along the chronic kidney disease (CKD) and transplant process (Table 1). Historical points of disparity have been demonstrated in:

TABLE 1:

Summary of Select Studies Describing Racial-ethnic Disparities in Pediatric Kidney Transplantation

Study	Population Source	Population Dates	Era	Population Age	Findings
DISPARITIES IN WAITLISTING
Furth et al. 2000	USRDS	1998–1993	Pre-Share 35	≤ 19 years	Black children and adolescents 12% less likely to be waitlisted. Finding magnified by SES.
Patzer et al. 2012	USRDS	2000–2008	ND	< 21 years	Black 18- to 20-year-olds had 16% lower access to waiting list.
Nguyen et al. 2011	NAPRTCS	1992–2005	ND	< 21 years	Black and Hispanic patients were more or equally likely to be listed following dialysis initiation.
Charnaya et al. 2023	USRDS and SRTR	2010–2014	Pre-KAS	<18 years	14% lower likelihood of waitlisting within 2 years in Black children.
Charnaya et al. 2023	USRDS and SRTR	2015–2019	Post-KAS	<18 years	33% and 18% lower likelihood of waitlisting within 2 years in Black and Hispanic Children, respectively.
DISPARITIES IN PRE-EMPTIVE TRANSPLANTATION
Patzer et al. 2013	USRDS	2000–2009	ND	< 18 years	Black children 66% less likely and Hispanic children 52% less likely to receive living donor preemptive transplant.
DISPARITIES IN TIME FROM WAITLIST TO TRANSPLANT
Laster et al. 2017	LDO	2001–2011	ND	<21 years	39% and 12% lower likelihood of transplant in Black and Hispanic.
Patzer et al. 2012	USRDS	2000–2008	ND	< 21 years	Black and Hispanic 18- to 20-year-olds had 39% and 34% lower transplantation rates, respectively.
Amaral et al. 2012	USRDS		Pre-Share 35	<18 years	Hispanic children had 22% lower likelihood of transplant. Black children had 18% lower likelihood of transplant (nonsignificant).
Amaral et al. 2012	USRDS		Post-Share 35	<18 years	No significant racial-ethnic difference in time to transplant. 81% higher likelihood of transplant in Hispanic compared to Hispanic in pre-Share 35.
Krissberg et al.	SRTR	2008–2019	Pre-KAS	<18 years	No racial differences in time from waitlist activation to transplant. 20% and 13% longer time on dialysis in Black and Hispanic respectively.
Krissberg et al.	SRTR	2008–2019	Post-KAS	<18 years	No racial differences in time from waitlist activation to transplant. No difference in time on dialysis in Black and Hispanic.
Charnaya et al. 2023	USRDS and SRTR	2015–2019	Pre-and-post-KAS	<18 years	No racial differences in time to deceased donor kidney transplant
Engen et al.	OPTN	2009–2019	Pre-and-post-KAS	Children and adults waitlisted prior to age 18 year	Transplant rate rose 14.5% in Caucasian patients but was unchanged in Black and Hispanic. Black children had lowest deceased donor rate pre-and-post KAS.
DISPARITIES IN LIVING DONATION
Amaral et al. 2020	USRDS	1995–2000	Pre- Share 35	<18 years	Black, Hispanic and Asian children 62%, 46%, 63% less likely to receive living donor transplant within 2 years of ESRD
		2011–2015	Post-Share 35	<18 years	Black, Hispanic and Asian children 66%, 42%, 39% less likely to receive living donor transplant within 2 years of ESRD
Charnaya et al. 2023	USRDS and SRTR	2015–2019	Pre-and-post KAS	<18 years	Amongst transplant recipients, 17.7% were living donation in Black patients, 50.6% were living donation in White patients.
DISPARITIES IN TRANSPLANT OUTCOMES
Omoloja et al.	NAPRTCS	1987–2005	ND	≤ 21 years	Black patients had higher risk of graft failure when compared to White patients (HR 1.65; 95% CI 1.46, 1.86).
Patzer et al. 2015	USRDS	2000–2011	Pre-and-post Share 35	<18 years	Rates of graft failure in Black children 82% higher than White children for both living and deceased donor.
Charnaya et al. 2023	USRDS and SRTR	2015–2019	Pre-and-post KAS	<18 years	The disparity in 5-year deceased donor graft failure between Black and White children noted pre-KAS was attenuated post-KAS.
Becerra et al. 2022	USRDS	1980–2017	ND	Children and adults who began KRT <18 years	Black patients spent 24% less time with a functioning transplant compared to White patients.
INTERNATIONAL DISPARTIES IN TRANSPLANTATION
Tjaden et al. 2016	ESPN/ERA-EDTA	2006–2012		≤ 19 years	Black and Asian children were 51% and 46% less likely to receive a kidney transplant compared to White children.
Grace et al. 2014	ANZDATA (New Zealand only)	1990–2012		<18 years	Pacific and Maori children were 63% and 75% less likely than European to receive a kidney transplant. This is largely due to differences in living donation. Pacific and Maori children had lower 5-year graft survival.

ND: Not Distinguished

SES: socioeconomic status

USRDS: United States Renal Data System

NAPRTCS: North America Pediatric Renal Trials and Collaborative Studies

SRTR: Scientific Registry of Transplant Recipients

KAS: Kidney Allocation System

LDO: Large Dialysis Organization

OPTN: Organ Procurement and Transplantation Network

KRT: Kidney Replacement Therapy

ESPN/ERA-EDTA: European Society of Pediatric Nephrology/European Renal Association-European Dialysis and Transplant Association

ANZDATA: Australia and New Zealand Dialysis and Transplant Registry

1. Pre-emptive transplantation or transplantation prior to the initiation of dialysis

2. Access to the waitlist once dialysis has been initiated

3. Timing to a deceased donor kidney transplantation (DDKT) once entering the waitlist

4. Access to living donor kidney transplantation (LDKT)

5. Graft survival and post-transplant outcomes

Racial disparities in waitlisting and preemptive transplantation

One of the earliest studies to illuminate disparities in kidney transplantation was published in 2000 by Furth et al. [1]. In a study of 2,162 White and 1,122 Black children and adolescents within the United States Renal Data System (USRDS) with dialysis incidence between 1988–1993, the authors demonstrated that Black children and adolescents were 12% less likely than White children and adolescents to be waitlisted despite consideration of age, socioeconomic status, and cause of kidney disease. Notably, stratified analysis demonstrated that Black participants in the lowest socioeconomic quartiles were 16% less likely than White participants to be activated. Contrarily, there were no racial differences in the highest socioeconomic quartile. This suggests a potential role of higher socioeconomic status in mitigating racial disparities in waitlisting. A later study by Patzer et al. using USRDS data between 2000 to 2008 also demonstrated decreased access to waitlisting, particularly in Black adolescents aged 18 to 20 years [2]. Despite equivalent waitlist access in children aged 0–17 years, when compared to White adolescents, Black 18- to 20-year-olds had 16% lower access to the waiting list even after the consideration of socioeconomic status. These studies highlight the intersectionality of racial and ethnic disparities, which manifest not only by race, but also according to patient age and SES. Contrary findings were noted in a study of pediatric patients (less than 21 years) in the North America Pediatric Renal Trials and Collaborative Studies (NAPRTCS) between 1992 to 2005 [3]. In this study of 4,473 children and young adults initiating dialysis between 1992 to 2005, Nguyen et al. found that Black patients were more likely than White patients to be placed on the waiting list at dialysis initiation and equally likely at later timepoints following the initiation of dialysis. Similarly, the same was seen in Hispanic children who were more likely to be listed at 12 months following dialysis initiation and equally likely at other time points. This geographically heterogeneous study of children from the United States, Canada, Mexico and Costa Rica underscores the complex nature of disparities and the likelihood of complex associations according to geographic location.

In addition to decreased likelihood of waitlisting, a study by Patzer et al. evaluating children in the USRDS between 2000 and 2009 revealed that Black children were also less likely than White children to receive a pre-emptive kidney transplant [4]. This finding was specifically related to living donor pre-emptive transplantation which Black children were 66% less likely to receive. Additionally, Hispanic children were 52% less likely to receive a living donor pre-emptive kidney transplant when compared to White children.

Overtime, policy changes by the United Network for Organ Sharing (UNOS) in the allocation of kidneys have been introduced to address disparities in transplantation. For instance, the Kidney Allocation System (KAS) implemented in 2014, attempts to lessen the impact of delays in waitlisting by equating wait time to total dialysis time. This is a critical change given recent studies demonstrating the persistence of disparities in waitlisting [5]. Using USRDS and Scientific Registry of Transplant Recipients (SRTR) data, an analysis by Charnaya et al. demonstrated 33% and 18% lower likelihood of waitlisting within 2 years of first kidney replacement service in Black and Hispanic children, respectively, post-KAS [5]. Of note, in the pre-KAS era, there was a 14% lower likelihood of waitlisting within 2 years between Black and White children suggesting a growth in this disparity post-KAS. Contrarily, post-KAS, children of Asian descent and those who were categorized as other race, were more likely than White children to be waitlisted. Notably, both groups were small in number relative to the groups of Black, White and Hispanic children. This is key to remember given the ethnic heterogeneity of both the “Asian” and “other” categories, which impedes the generalization of these findings. Unfortunately, while the KAS policy changes address the impact of lost waiting time, it does not directly facilitate equitable waitlisting which may impact overall wait time and risk of dialysis-related comorbidities.

Time from waitlist to transplant

In addition to historical descriptions of racial disparities in time to waitlisting, disparities in time from waitlisting to transplant have also been described. When considering disparate mortality rates as a competing risk, Laster et al. demonstrated 39% (HR=0.61; 95% CI 0.52–0.71) and 12% (HR=0.88; 95% CI 0.76–1.02) lower likelihood of transplantation in Black and Hispanic children (< age 21 years), respectively [6]. A study by Patzer et al. assessed this disparity by age and discovered that racial disparities were most evident amongst Black and Hispanic adolescents 18-to-20 years of age. In this age group, rates of deceased donor transplantation were 39% (HR=0.61; 95% CI 0.49–0.76) and 34% (HR=0.66; 95%CI 0.51–0.86) lower when compared to White adolescents after adjustment for clinical and SES factors [2]. By contrast, the 0-to-17-year age group did not show as great of a racial-ethnic difference in time from waitlisting to deceased donor transplant (HR 0.89; 95%CI 0.8–0.99 in Black and 0.97; 95%CI 0.86–1.08 in Hispanic vs. White]. This study highlights the magnification of this racial-ethnic disparity amongst the 18- to 20-year-old age group. Of note, the interpretation of studies that include young adults (18 years and older) must consider differences in organ allocation as this age group may be subject to adult allocation policies.

Disparities in time to transplant are marked in time by major changes in the allocation of organs to pediatric patients. For instance, Share 35, enacted by UNOS in 2005, gave preferential allocation of deceased donor kidneys from donors less than 35 years to pediatric patients less than 18 years old [7]. A study by Amaral et al. concluded that prior to this policy change, Black and Hispanic children (≤ age 17 years) were less likely to receive a transplant after being waitlisted. This finding was statistically significant amongst Hispanic children who demonstrated a 22% lower likelihood of transplant (HR 0.78; 95% CI 0.61–0.99). Although not significant amongst Black children, there was a trend toward lower transplantation with 18% lower likelihood of transplantation than White children (HR 0.82; 95% CI 0.67–1.02) [7]. After Share 35, all pediatric patients had an increased probability of transplantation and experienced shorter wait times with Hispanic children experiencing the greatest reduction in wait time and an 81% higher probability of transplant compared to the pre-Share 35 era (HR=1.81; 95% CI 1.48–2.21 vs. Hispanic pre-Share 35) [7].

To determine the impact of the kidney allocation system of 2014 on racial-ethnic disparities, Krissberg et al. used SRTR data between 2008 to 2019 and concluded there were no racial differences in the time from waitlist activation to transplantation in the pre or post KAS eras [adjusted time ratio (aTR) pre-KAS 1.14; 95% CI 1–1.29 in Black, 1.12; 95% CI 0.99–1.28 in Hispanic; post-KAS 1.16; 95% CI 1.01–1.32 in Black, 1.13; 95%CI 1–1.28 in Hispanic). Black and Hispanic children did tend toward longer adjusted time on dialysis in the pre-KAS era but this was no longer significantly different post-KAS (aTR pre-KAS 1.2; 95% CI 1.09–1.32 in Black, 1.13; 95% CI 1.02–1.24 in Hispanic; post-KAS 1.1; 95% CI 0.99–1.24 in Black, 1.03; 95% CI 0.93–1.15 in Hispanic) [8]. This change may reflect the change in wait time calculation instituted by the KAS whereby wait time includes total dialysis time. Similar to Krissberg et al., Charnaya et al., using USRDS and SRTR data to analyze pre and post-KAS transplant rates between 2010 and 2019, demonstrated no racial differences in time to deceased donor kidney transplant within the 4–5 years before the KAS was implemented, nor in the years after KAS implementation [5]. The lack of pre-KAS disparities in time from waitlist activation to transplantation described by both Krissberg et al. and Charnaya et al. likely reflect the improvements in racial-ethnic disparities described by Amaral et al. following the institution of Share 35 [7]. Still, despite a general finding that disparities are unchanged pre- and post-KAS, a study by Engen et al. demonstrated that the 8.3% increase in the deceased donor rate experienced by pediatric patients post-KAS was not experienced amongst Black and Hispanic patients who had no significant change in transplantation rates. Additionally, in this study, Black children continued to have the lowest rate of deceased donor transplantation amongst all races [9].

Racial Disparities in Living Donation

In addition to racial-ethnic differences in deceased donor transplantation, significant differences in living donor transplantation exist as well. Investigating pediatric living donor kidney transplants (LKDT) within the USRDS, Amaral et al. found that, between 1995 to 2000, when compared to White children, Black children were 62% less likely to receive a living donor transplant within 2 years of diagnosis with kidney failure. During the same period, Hispanic children were 46% less likely, and Asian children were 63% less likely to receive a LDKT within 2 years of kidney failure [10]. Following the Share 35 policy of 2005, there was a general decline in living donor transplants amongst pediatric patients. In the most contemporary era of this study (2011 to 2015) disparities in LDKT and the magnitude of these disparities persisted for Black and Hispanic children whereas LDKT disparities improved but remained for Asian children making them 39% less likely than White children to receive a LDKT [10]. Charnaya et al. also demonstrated a relatively lower frequency of LDKT within Black patients (17.7% of transplants received by Black patients) and the highest frequency within White patients (50.6%) [5]. Although more studies evaluating factors that contribute to LDKT disparities are needed within pediatric nephrology, adult studies suggest racial differences in completion of the LDKT evaluation process as a key factor [10].

Kumar et al. discovered that Black potential donors were 53% (HR 0.47; 95% CI 0.26, 0.83) less likely than non-Black donors to progress from referal to donation and, even after medically cleared, Black potential donors were 38% (HR 0.62; 95% CI 0.41, 0.94) less likely to progress to donation [11]. Reasons for non-donation varied and the overall proportion of donor-related factors (as opposed to recipient-related factors) preventing donation was similar between Black and non-Black potential donors (68% vs. 60%, respectively). Of note, within those donor-related factors, Black potential donors had higher frequency of non-donation due to medical factors including obesity, hypertension, and kidney abnormalities (42% vs. 26%). Both Black and non-Black potential donors reported unspecified social factors (10% and 8%, respectively) and unspecified personal factors (16% and 17%, respectively) preventing donation [11]. Therefore, medical factors are a potential mechanism by which disparities in living donation arise.

In addition to medical factors, donor income also plays a critical role in successful living kidney donation. In a study using US Census data, the incidence of Black and White donors across five income levels was compared using UNOS-registered living donors relative to the potential living donation pool matched by income and race [12]. The authors concluded that racial differences in the incidence of living kidney donation varied according to income level as represented by median household income. In the lower income quintile, the incidence of living kidney donation was lower in the Black population but in the top three quintiles, the incidence of living kidney donation was higher in the Black population as compared to the White population. Whereas previous studies demonstrate an important role of medical misinformation and mistrust in the completion of the living donation process, these findings highlight the significant role of socioeconomic factors as well [12, 13].

Long-term Transplant Outcomes

Unfortunately, after navigating disparities in receiving a transplant, further disparities can be seen in graft outcomes between racial-ethnic groups. In a study performed using NAPRTCS data from 2007, Omoloja et al. illustrated significantly lower graft survival in Black as compared to White children and a worsening of these disparities with increased time from transplant. For example, at three years post-transplant, 88.8% of White pediatric patients had surviving grafts while 76.9% of Black patients had surviving grafts. At five years post-transplant, 83.1% of White patients had surviving grafts while 65.6% of Black patients had surviving grafts [14]. Overall, Black patients had a 65% higher adjusted risk of graft failure when compared to White patients. Similarly, Patzer et al. examined the association of race and ethnicity and kidney allograft survival by analyzing 6,216 pediatric patients with kidney failure from the USRDS who received transplants between 2000 and 2011. Like the previous study, there was a disparity in 5-year graft survival amongst racial groups. The 5-year graft survival rate for living donor transplants was 78.9% in Black participants, 90.8% in Hispanic participants and 93.0% in White participants. For deceased donor transplants, the five-year graft survival rate was 63.0% for Black, 82.8% for Hispanic, and 92.2% for White participants [15]. Upon adjustment, Black children had 82% higher risk of graft failure for both living and deceased donor transplants when compared to White children.

Although somewhat improved post-KAS initiation, disparities in all cause graft failure have persisted amongst children receiving DDKT. In the USRDS/SRTR study by Charnaya et al., before the implementation of KAS, Black children had 75% higher hazard of all cause 5-year graft failure when compared to White children. After KAS this disparity decreased to 43% with attenuation of the statistical significance in the difference between the groups [5]. Overall, the risk of all-cause graft failure amongst Black children decreased by 44% when compared to pre-KAS rates. This decrease occurred despite less favorable transplant factors amongst Black children including a greater frequency of delayed graft function, lower frequency of living kidney receipt and higher HLA mismatching in Black children. Given the overall increase in the frequency of grafts with KDPI <20%, it is possible that the allocation of more favorable grafts has impacted the disparity in graft survival, albeit imperfectly. The lingering disparity may reflect the presence of described disparities in delayed graft function, HLA mismatching and living donation seen post-KAS.

The significance and long-term impact of these disparities in allograft function is well captured by Becerra et al. in a USRDS study of 28,000 patients with initiation of kidney replacement therapy (transplant or dialysis) before 18 years of age. The authors demonstrated that Black patients had shorter time with successful functioning allografts with a median of 6.1 years (IQR 2.6–11.7) in comparison to White patients with a median of 10.3 years (IQR 4.8–17.7). Over 30 years of observation, Black patients spent a median of 57% (IQR 27%−83%) of their follow-up time with a functioning graft compared to 83% (IQR 56%- 97%) in White patients. Altogether, Black patients spent 24% less of their kidney replacement therapy (KRT) with a functioning transplant than White patients [16]. Becerra et al. estimated that 35% of the morality disparity seen between these ethnic groups could be reduced by the equalization of transplantation including access to transplantation, access to re-transplantation and time spent with a functional graft. Overall, racial disparities in graft survival are improved but persistent. Several factors may contribute to the lingering disparity including less frequent living donor receipt, higher HLA-mismatching, older age at transplantation amongst Black children and currently incompletely measured socioeconomic factors [5,8].

International Disparities in Transplantation

Thus far, the described disparities have largely reflected North American populations of children and young adults but disparities in transplantation by race have been demonstrated internationally. In one of the first studies to define disparities in a large European cohort, Tjaden et al. analyzed 1,134 children and young adults less than 19 years old from 36 medium to high income European countries. They found that Black and Asian children had a longer time from kidney replacement therapy initiation to kidney transplantation (25.1 months in Black, 23.5 months in Asian vs. 12.5 months in White). In adjusted analysis, Black and Asian children were 51% (HR 0.49; 95% CI 0.34–0.72) and 46% (HR 0.54; 95%CI 0.41–0.71) less likely than White children to receive a kidney transplant, respectively. There were no racial differences in graft survival in this European study [17]. In a study of pediatric patients in New Zealand, racial disparities were described between Pacific and Maori patients when compared to European patients [18]. For context, the racial breakdown of the population by census estimates at the time of this study was: 72.7% European, 23.4% Maori, 11.8% Pacific and 9.9% Asian (residents can be listed under multiple groups) [18]. In this population of 215 children, less than 18 years of age between 1990–2012, Pacific and Maori patients were less likely than European patients to receive a kidney transplant (HR 0.37; 95% CI 0.22, 0.63 and HR 0.25; 95 % CI 0.16, 0.40, respectively). This difference was largely driven by differences in living donation and preemptive donation which were both lower in Pacific and Maori patients when compared to European patients. Factors contributing to lower living donation in these populations have been described and include a lower availability of potential donors, exclusion of donors due to medical reasons including obesity and abnormal glucose tolerance, and socioeconomic barriers to the donor evaluation process [19]. Pacific and Maori patients also had lower 5-year death-censored graft survival than European patients. This was lowest in Pacific patients who had a survival of 31% compared to 61% and 88% in Maori and European patients, respectively. Notably, Pacific and Maori patients were more likely to be sensitized, had more HLA mismatches and were more likely to have delayed graft function. Pacific patients also had higher rates of graft loss due to FSGS which may impact these outcomes [18]. Therefore, the contributors to disparities in graft survival are varied and require further assessment.

Drivers of disparities in transplantation

With time, more attention is being given to the social determinants of health and how they impact transplant access and outcomes [20]. Social determinants of health are “the conditions in the environments where people are born, live, work, play, worship, and age that affect a wide range of health, functioning, and quality of life outcomes and risks” [21]. A study by Christofferson et al. sought to understand barriers associated with pediatric transplant evaluation and listing amongst children ages 0 to 18 years in need of heart, liver or kidney transplants between 2012 to 2015. They discovered that minority status was associated with an increased risk of financial barriers and social barriers (social services involvement, abuse or neglect, lack of parental supervision, unstable home environment) and that these barriers were associated with increased time to listing [22]. In one of few studies evaluating language barriers to kidney transplantation in children, Kerkvliet et al. demonstrated that, although there were no differences in 5-year graft survival between English-speaking (ES) and Interpreter-needing (IN) recipients, IN recipients were older at the time of transplant and waited longer for a transplant. IN recipients additionally had lower adjusted 5-year post-transplant survival, despite no difference in death-censored graft survival [23]. Although it remains to be determined how language barriers may act as a mediator of survival differences, this study suggests that language barriers may impede timing to transplantation in pediatric patients. In a study of adults, Wesselman et al. comprehensively assessed social determinants and the likelihood of kidney transplant. In addition to racial differences noted in the likelihood of transplantation, greater religious objections to transplantation, lower income, less transplant knowledge and less social support were associated with decreased likelihood of transplantation [24]. These studies demonstrate that zeroing in on social determinants that impact transplant allows for an understanding of mechanisms at play that are not portrayed by the use of race and ethnicity alone. Furthermore, these areas provide guidance on potential interventions to improve transplant access.

Because race is most reflective of the ill-defined and discriminatory social constructions introduced in the mid-17^th century, careful consideration must be taken when theorizing biological drivers of racial disparities [25]. Prior studies have suggested immunologic differences by race including differences in cellular immune responses, cytokine production and in the dosages of immunosuppressant needed to prevent rejection. Of note, some of these differences are associated with differences in the racial distribution of key polymorphisms within genes encoding cytokines and enzymes responsible for drug metabolism [26]. Still, studies to further define these differences and determine the impact on patient care and disparities are lacking. Importantly, as stated by Padiyar et al., immune factors alone do not explain the differences seen in transplant outcomes. Therefore, approaches which further define the social determinants impacting transplant outcomes and that consider the interaction between social and biological factors are still needed.

Summary

In summary, racial disparities in transplant access after waitlisting show evidence of improvement overtime. Still, disparities remain in key areas including preemptive transplantation, access to the waitlist, living donation and long-term allograft outcomes. Preemptive transplantation is likely a function of timing of presentation to nephrology care and chronic kidney disease progression, the latter of which is faster amongst Black children and associated with shorter time to dialysis [27]. Disparities in living donation likely contribute to these disparities in preemptive transplantation as well. Thus, measures to address disparities in pre-emptive transplantation must look at factors affecting CKD presentation, particularly, barriers related to access to care and better understand barriers to living donation in the pediatric population. The persistence of disparities in long-term transplant outcomes threatens to reverse any improvements seen as a result of improved transplantation access. Given evidence that time spent with a functioning graft is related to disparities in survival, it is critical that we better understand and eventually intervene upon the factors contributing to disparities in long-term graft outcomes [16]. Consideration of the social determinants of health of our patients is critical to this endeavor [28].