Racial/Ethnic Disparities in Waitlisting for Deceased Donor Kidney Transplantation 1 Year After Implementation of the New National Kidney Allocation System

Xingyu Zhang; Taylor A. Melanson; Laura C. Plantinga; Mohua Basu; Stephen O. Pastan; Sumit Mohan; David H. Howard; Jason M. Hockenberry; Michael D. Garber; Rachel E. Patzer

Disclosures

American Journal of Transplantation. 2018;18(8):1936-1946. 

In This Article

Abstract and Introduction

Abstract

The impact of a new national kidney allocation system (KAS) on access to the national deceased–donor waiting list (waitlisting) and racial/ethnic disparities in waitlisting among US end–stage renal disease (ESRD) patients is unknown. We examined waitlisting pre– and post–KAS among incident (N = 1 253 100) and prevalent (N = 1 556 954) ESRD patients from the United States Renal Data System database (2005–2015) using multivariable time–dependent Cox and interrupted time–series models. The adjusted waitlisting rate among incident patients was 9% lower post–KAS (hazard ratio [HR]: 0.91; 95% confidence interval [CI], 0.90–0.93), although preemptive waitlisting increased from 30.2% to 35.1% (P < .0001). The waitlisting decrease is largely due to a decline in inactively waitlisted patients. Pre–KAS, blacks had a 19% lower waitlisting rate vs whites (HR: 0.81; 95% CI, 0.80–0.82); following KAS, disparity declined to 12% (HR: 0.88; 95% CI, 0.85–0.90). In adjusted time–series analyses of prevalent patients, waitlisting rates declined by 3.45/10 000 per month post–KAS (P < .001), resulting in ≈146 fewer waitlisting events/month. Shorter dialysis vintage was associated with greater decreases in waitlisting post–KAS (P < .001). Racial disparity reduction was due in part to a steeper decline in inactive waitlisting among minorities and a greater proportion of actively waitlisted minority patients. Waitlisting and racial disparity in waitlisting declined post–KAS; however, disparity remains.

Introduction

Kidney transplantation is generally preferred over dialysis for treatment of end–stage renal disease (ESRD) because it is associated with substantially better outcomes than dialysis.[1] However, there is a severe shortage of organs for transplantation, forcing organ allocation policies to balance both equity and utility in their design.[2] Many countries established their own deceased kidney organ allocation system to strike a balance between efficient use of and equal access to the deceased organs for deceased donor transplantation.[2] In the United States, only ≈15% of ESRD patients were waitlisted for kidney transplantation, and ≈19 000 patients received a transplant in 2016 among the 103 114 people currently on the waitlist.[3,4] Despite policy regulations of the Department of Health and Human Services that require organs to be allocated equitably,[5] there are racial and ethnic disparities at each step of the kidney transplant process. Black patients are less likely to be referred for transplant,[6] complete the evaluation process if referred,[7] be placed on the waiting list,[7,8] and receive a transplant[9–16] compared to white patients. In addition, Hispanics have historically had lower transplant rates after waitlisting.[17] Disparities are the result of many potential factors, such as poverty,[18–20] geography,[8,20,21] limited education about transplant,[15,22] physician bias,[23] and other system–level factors, such as federal policies that guide US organ allocation.[24,25]

The new kidney allocation system (KAS)[26] was implemented by the United Network for Organ Sharing (UNOS) in December 2014 in part to improve equity related to dialysis time, and to the group of patients with high panel–reactive antibody.[27] More specifically, changes that were likely to benefit minority patients include the change in the calculation of waiting time, which now starts at dialysis start instead of waitlist, and prioritization of the most sensitized patients, who are disproportionately more likely to be minorities. Changes in allocation priority were intended to improve kidney allocation disparities among different races/ethnicities on the waiting list.[28] Prior to KAS implementation, simulations predicted that black vs white racial disparities in transplantation among patients already on the transplant waiting list would decrease by 6% within 1 year.[3,29] Subsequent research has confirmed these hypotheses, where racial/ethnic disparities in deceased–donor transplant among waitlisted patients have been at least temporarily eliminated.[30,31] However, it is unknown how the new KAS policy may have influenced access to the waiting list. It is possible that the implementation of KAS led to increased referrals for transplant evaluation and higher waitlisting, particularly among patients who spent a longer time on dialysis and who were not previously referred or waitlisted for transplant. Because minorities tend to spend longer on dialysis prior to referral for transplantation,[32] the policy change may have differential effects by racial/ethnic group. However, it is also possible that the policy has reduced the sense of urgency to refer some patients who may have only recently started dialysis. Delayed referral to transplant for minority patients could further exacerbate the racial/ethnic disparities in living donor transplantation, which is the optimal treatment for ESRD patients.[33] Thus, the influence of KAS on waitlisting and waitlisting disparities may differ between the incident and prevalent ESRD populations.

The aims of this study were (1) to assess the impact of the 2014 KAS policy change on waitlisting overall, and (2) to evaluate whether racial/ethnic disparities in waitlisting in the United States changed following the policy's implementation. We performed 2 types of analyses to achieve these aims: (1) a time–to–event analysis to examine how KAS affected time from dialysis start to waitlisting among the incident ESRD population, and (2) a trend analysis to examine how the new KAS policy affected monthly waitlisting rates among prevalent (existing) dialysis patients not already on the waiting list.

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