A Donor Risk Index for Graft Loss in Pediatric Living Donor Kidney Transplantation

Heather L. Wasik; Cozumel S. Pruette; Rebecca L. Ruebner; Mara A. McAdams-DeMarco; Sheng Zhou; Alicia M. Neu; Dorry L. Segev; Allan B. Massie

Disclosures

American Journal of Transplantation. 2019;19(10):2775-2782. 

In This Article

Abstract and Introduction

Abstract

Pediatric kidney transplant candidates often have multiple potential living donors (LDs); no evidence-based tool exists to compare potential LDs, or to decide between marginal LDs and deceased donor (DD) kidney transplantation (KT). We developed a pediatric living kidney donor profile index (P-LKDPI) on the same scale as the DD KDPI by using Cox regression to model the risk of all-cause graft loss as a function of living donor characteristics and DD KDPI. HLA-B mismatch (adjusted hazard ratio [aHR] per mismatch = 1.041.271.55), HLA-DR mismatch (aHR per mismatch = 1.021.231.49), ABO incompatibility (aHR = 1.203.268.81), donor systolic blood pressure (aHR per 10 mm Hg = 1.011.071.18), and donor estimated GFR (eGFR; aHR per 10 mL/min/1.73 m2 = 0.880.940.99) were associated with graft loss after LDKT. Median (interquartile range [IQR]) P-LKDPI was −25 (−56 to 12). 68% of donors had P-LKDPI <0 (less risk than any DD kidney) and 25% of donors had P-LKDPI >14 (more risk than median DD kidney among pediatric KT recipients during the study period). Strata of LDKT recipients of kidneys with higher P-LKDPI had a higher cumulative incidence of graft loss (39% at 10 years for P-LDKPI ≥20, 28% for 20> P-LKDPI ≥−20, 23% for −20 > P-LKDPI ≥−60, 19% for P-LKDPI <−60 [log rank P < .001]). The P-LKDPI can aid in organ selection for pediatric KT recipients by allowing comparison of potential LD and DD kidneys.

Introduction

Several studies have shown an association between donor characteristics and graft survival in deceased donor kidney transplantation (DDKT) and living donor kidney transplantation (LDKT) in adults.[1–6] The Kidney Donor Risk Index (KDRI) and related Kidney Donor Profile Index (KDPI) were created to quantify the risk of graft loss due to donor factors in adult DDKT.[7] Recently, a living donor KDPI (LKDPI) was created to quantify the risk of graft loss due to donor factors in adults undergoing LDKT, on the same scale as the DD KDPI.[8] Thus, the LKDPI aids in organ selection by allowing for comparison of living donor (LD) kidneys to each other and to deceased donor (DD) kidneys.

There is no risk index to quantify the risk of graft loss based on donor characteristics in children undergoing LDKT. Based on Organ Procurement and Transplantation Network (OPTN) data from 2016, 34.2% of kidney transplants received by pediatric patients <18 years of age in the United States were from LD, and these patients received 4.4% of all LDKT.[9] A pediatric LDKT risk index that combines multiple donor factors to create a summary score of relative donor quality on the same scale as the DD KDPI would provide a clinically interpretable framework for quantifying donor risk. It would be useful in choosing a donor for pediatric patients who have multiple potential LDs. Furthermore, the current Kidney Allocation System (KAS) in the United States preferentially allocates high-quality DD kidneys to pediatric patients, so wait times for DD kidneys tend to be shorter for children compared to adults.[10] Thus, a pediatric LDKT risk index on the same scale as the DD KDPI would be helpful in making the decision to choose a DD kidney when a potential LD is available. Pediatric patients and families could also use an LDKT risk index to evaluate offers made through kidney paired donation (KPD).[11]

Several recipient factors that affect graft survival differ between children and adults, including immune factors, body size, potential for growth and development, and risk of primary viral infections.[12] These differences suggest that the impact of LD characteristics may vary between children and adults. For example, the LKDPI includes a variable for donor recipient weight ratio among donors with a ratio <0.9, and this variable is irrelevant for the many pediatric KT recipients who are smaller than their adult LDs.[8] Therefore, the LKDPI is not suitable for use in pediatric KT recipients.

To address the absence of a pediatric-specific LDKT risk index, we conducted a retrospective cohort study of first-time KT recipients in the United States using national registry data. The aims of this study were to determine LD characteristics associated with graft loss among pediatric patients undergoing LDKT, to create a pediatric-specific LD KDPI (P-LKDPI) on the same scale as the DD KDPI, and to assess the predictive validity of the P-LKDPI.

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