Trends in Usage and Outcomes for Expanded Criteria Donor Kidney Transplantation in the United States Characterized by Kidney Donor Profile Index

Abstract

There has been increasing concern in the kidney transplant community about the declining use of expanded criteria donors (ECD) despite improvement in survival and quality of life. The recent introduction of the Kidney Donor Profile Index (KDPI), which provides a more granular characterization of donor quality, was expected to increase utilization of marginal kidneys and decrease the discard rates. However, trends and practice patterns of ECD kidney utilization on a national level based on donor organ quality as per KDPI are not well known. We, therefore, performed a trend analysis of all ECD recipients in the United Network for Organ Sharing (UNOS) registry between 2002 and 2012, after calculating the corresponding KDPI, to enable understanding the trends of usage and outcomes based on the KDPI characterization. High-risk recipient characteristics (diabetes, body mass index ≥30 kg/m2, hypertension, and age ≥60 years) increased over the period of the study (trend test p<0.001 for all). The proportion of ECD transplants increased from 18% in 2003 to a peak of 20.4% in 2008 and then declined thereafter to 17.3% in 2012. Using the KDPI >85% definition, the proportion increased from 9.4% in 2003 to a peak of 12.1% in 2008 and declined to 9.7% in 2012. Overall, although this represents a significant utilization of kidneys with KDPI >85% over time (p<0.001), recent years have seen a decline in usage, probably related to regulations imposed by Centers for Medicare & Medicaid Services (CMS).When comparing the hazards of graft failure by KDPI, ECD kidneys with KDPI >85% have a slightly lower risk of graft failure compared to standard criteria donor (SCD) kidneys with KDPI >85%, with a hazard ratio (HR) of 0.95, a confidence interval (CI) of 0.94-0.96, and statistical significance of p<0.001. This indicates that some SCD kidneys may actually have a lower estimated quality, with a higher Kidney Donor Risk Index (KDRI), than some ECDs. The incidence of delayed graft function (DGF) in ECD recipients has significantly decreased over time from 35.2% in 2003 to 29.6% in 2011 (p=0.007), probably related to better understanding of the donor risk profile along with increased use of hypothermic machine perfusion and pretransplant biopsy to aid in optimal allograft selection.The recent decline in transplantation of KDPI >85% kidneys probably reflects risk-averse transplant center behavior. Whether discard of discordant SCD kidneys with KDPI >85% has contributed to this decline remains to be studied.

R Open Source Programming Code for Calculation of the Kidney Donor Profile Index and Kidney Donor Risk Index

“…At least in the USA, KDPI has a potential to influence the clinical decision on whether to accept or discard a donor kidney, but there is no uniform view on its robustness since the graft outcomes depend also on other donor factors and recipient characteristics. Up to now, there have been a lot of debates about KDPI, and while some authors found its use increased the acceptance of donors and lead to rise in transplantation rate [7] and robustly predicted kidney graft survival [8], others doubted about its generalizability to non-US [9] and non-adult populations [10, 11], and caution about formal KDPI use as a criterion of organ discard [12, 13]. KDPI > 85% is thought to be equivalent to an extended criteria donor (ECD) kidney (while the KDPI is based on 10 parameters, the historical ECD definition is based on only 4 parameters), but almost twice less donors were classified as ECD according to KDPI> 85% in comparison with the historical ECD definition, and thus were accepted for transplantation [12].…”

“…KDPI > 85% is thought to be equivalent to an extended criteria donor (ECD) kidney (while the KDPI is based on 10 parameters, the historical ECD definition is based on only 4 parameters), but almost twice less donors were classified as ECD according to KDPI> 85% in comparison with the historical ECD definition, and thus were accepted for transplantation [12]. However, the usage of kidneys with higher KDPI, and particularly > 85%, has declined in the USA [12, 13], that leaves some potential recipients on dialysis. Of note, even the recipients of kidneys with KDPI > 85% were at a much lower risk of death 2 years after transplant compared to those remaining on dialysis waiting for low-KDPI kidneys [13].…”

Analysis of local versus imported expanded criteria donor kidneys: A single‐center experience with 497 ECD kidney transplants

“…For all intents and purposes, the “ECD era” in the United States ended on December 4, 2014, at which time UNOS implemented the new Kidney Allocation System (KAS) . In lieu of using a binary system of deceased donor classification (ECD vs SCD), the new KAS categorizes donor kidneys based on a 10‐variable Kidney Donor Profile Index (KDPI) . A KDPI score of 85% or higher approximates the previous ECD labeling .…”

“…In lieu of using a binary system of deceased donor classification (ECD vs SCD), the new KAS categorizes donor kidneys based on a 10‐variable Kidney Donor Profile Index (KDPI) . A KDPI score of 85% or higher approximates the previous ECD labeling . Acknowledging that an ECD kidney is best defined by limited nephron mass, we have previously reported good intermediate outcomes with ECD kidneys by attempting to match estimated donor nephron functional capacity with anticipated lower recipient nephron need .…”

Invited letter in response to: “Is the kidney donor profile index (KDPI) universal or UNOS-specific?”

“…4 As suggested by Ekser and coworkers, 2 this major limitation could be addressed by selecting and allocating older kidneys on the basis of biopsy findings. With this approach, the donor pool could be expanded without affecting transplant outcomes.…”