Each year, nearly 5000 people in the United States and more than 3000 in Europe die while waiting for a kidney transplant. The shortage of organs available for transplant is a major public health issue, due to wait-listed patient mortality as well as increased healthcare costs of maintaining patients with end-stage renal disease (ESRD) on chronic dialysis. However, more than 3500 kidneys are discarded in the United States annually.
Results of recent studies have suggested that even the lowest-quality kidneys prolong survival compared with dialysis in patients with ESRD. Explanations for the high rate of kidney discard in the United States include the intense regulatory scrutiny of US transplant programs, financial disincentives, and the role of kidney biopsy as a method of determining allograft quality. Transplant programs in France face less regulatory scrutiny and do not use donor kidney biopsies in organ acceptance decisions.
Despite two initiatives from the United Network for Organ Sharing, the number of discarded kidneys rose from 2127 (14.9%) in 2006 to 3631 (20%) in 2016 in the United States. Researchers, led by Oliver Aubert, MD, PhD, conducted a study to compare the US transplant system with the French system. Results were reported online in JAMA Internal Medicine [doi:10.1001/jamainternmed.2019.2322].
The cohort study analyzed the use of 156,089 deceased donor kidneys in the United States and 29,984 in France, and used computer simulation algorithms to measure the potential gains in allograft survival years that would result if US programs adopted less restrictive kidney acceptance practices.
The French cohort included 15,500 deceased donors between January 1, 2004, and December 31, 2014, from whom the 29,984 kidneys were recovered. Of the recovered kidneys, 27,252 were transplanted and 2732 (9.1%) were discarded. In the US cohort (n=78,517) of deceased donors between 2004 and 2014, 156,089 kidneys were recovered for transplantation. Of those, 128,102 were transplanted and 27,987 (17.9%) were discarded.
Of the transplanted kidneys, mean donor age in France was 50.91 years versus 36.51 years in the United States (P<.001). A smaller percentage of donors in the United States had hypertension compared with donors in France (24.76% vs 29.06%; P<.001), or died of cerebrovascular causes (32.68% vs 54.57%; P<.001). In France, kidneys were less likely to be donated following cardiac death (prevalence rate of 1.6% vs 11.7% in the United States) and to come from donors seropositive for hepatitis C virus (prevalence rate of 0.1% vs 2.1% in the United States).
The discard rate in France was lower for weekend procurement: 667 kidneys were discarded during the weekend (8.5%) compared with 2065 discarded during weekdays (9.3%), P=.02. The overall discard rate in the United States was similar during the weekdays and weekend: 20,273 kidneys were discarded during the weekdays compared with 7750 discarded during the weekend (prevalence rate of 17.9% vs 18.0%, respectively; P=.70). There was a higher discard rate of kidneys recovered from African American donors (4748/22,751; 20.9%) versus non-African American donors (23,239/133,338; 17.43%), P<.001.
The mean Kidney Donor Risk Index (KDRI) of transplanted deceased donors was significantly higher in France than in the United States (1.50 vs 1.23; P<.001). Trends observed using the Kidney Donor Profile Index (KDPI) score were similar.
In France, there was a steady rise in KDRI from 2004 through 2014 (mean, 1.37 in 2004 and 1.74 in 2014; P<.001), reflecting a temporal trend of more aggressive organ use. In contrast, there was little change in the quality of kidneys transplanted in the United States during the study period (mean KDRI, 1.30 in 2004 and 1.32 in 2014). Trends observed using the KDPI score were similar. Increasing donor age was the principal driver of the higher KDRI in France: in 2014, the mean donor age in France was 56.17 years versus 39.08 years in the United States.
Results of prediction models for kidney discard decisions in France and the United States showed a strong association between the KDRI and discard of the kidney in both France and the United States (odds ratio [OR], 3.88; 95% confidence interval [CI], 3.83-3.93 in the United States; OR, 2.18; 95% CI, 2.07-2.30 in France; P<.001). The two models showed good accuracy, with an area under the curve (AUC) of 0.82 for the United States model and an AUC of 0.72 for the French model; calibration was excellent in both models.
The US allocation system had a higher probability of discarding kidneys with higher KDRIs than in France. A KDRI of 1, 2, 3, and 4 results in actual kidney discard rates of 5%, 45%, 80%, and 92%, respectively, in the United States, compared with 3%, 13%, 27%, and 42% discard rates in France, respectively.
Application of the French allocation model to the US cohort demonstrated that a French-based practice pattern translated to an estimated 10,552 discarded kidneys compared with the actual number of 27,987 discarded kidneys in the United States; the French model-based discard rate was 6.8% versus the actual discard rate in the United States of 17.9%. Overall, the use of the French-based discard practice pattern would have corresponded to an estimated 17,435 fewer discarded kidneys (62.3% among all discarded kidneys) in the United States during the study period 2004 to 2014.
A final analysis demonstrated that a redesigned system in the United States with more aggressive organ acceptance practices would generate an additional 132,445 allograft life-years over the 10-year observation period.
Study limitations cited by the authors included unmeasured confounding by donor characteristics not assessed in the KDRI that may have contributed to international differences in organ discard rates; posttransplant outcomes for lower-quality kidneys might be worse in the United States compared with France; and policy in the United States does not preferentially allocate older kidneys to older recipients, creating the possibility that greater procurement of high-KDRI kidneys might have adverse consequences if those kidneys were transplanted into young recipients.
“The high discard rate of deceased donor kidneys is a major concern for the US transplant field. We found that the age and KDRI of US deceased donor kidneys remained stable from 2004 to 2014 in the United States, whereas the French transplant system responded to the organ shortage by accepting lower-quality kidneys, especially those from older donors,” the researchers said. “Policies designed to enhance the acceptance of donated kidneys in the United States could drive meaningful increases in the number of kidney transplants and bring the benefits of transplantation to thousands of wait-listed patients.”
- Researchers conducted a study to examine the effects of more aggressive allograft acceptance practices on the donor pool and transplant outcomes for wait-listed transplant candidates in the United States.
- The study modeled organ acceptance and discard practices in the United States and France to quantify the number of kidneys discarded in the United States that a more aggressive system would have used for transplantation.
- The analyses demonstrated that more aggressive organ acceptance practices would have resulted in an additional 17,435 kidneys for transplantation in the United States during the study period.