Transplantation Mediates Much of the Racial Disparity in Survival from Childhood-Onset Kidney Failure
Authors: Becerra Adan Z. , Chan Kevin E. , Eggers Paul W. , Norton Jenna , Kimmel Paul L. , Schulman Ivonne H. , Mendley Susan R. 
Published: January 2022

Significance Statement
Differences in survival between Black and White patients with childhood-onset kidney failure are recognized, but the impact of lifelong racial disparities in kidney transplantation on survival is not well characterized. In a 30-year observational cohort study of 28,337 children that extends into young adulthood, Black patients had a 45% higher risk of death, a 31% lower rate of first transplant, and a 39% lower rate of second transplant. Black patients had fewer living donor transplants than White patients. Children and young adults are likely to require more than one transplant during their lifetime, yet even after their first transplant Black patients received 11% fewer total lifetime transplants than White patients. Transplants failed earlier for Black patients after the first and second transplant. These combined disparities resulted in Black patients spending 24% less time being treated for kidney failure with a transplant than White patients. We estimate that 35% of excess deaths in Black patients with ESKD beginning in childhood would be prevented if their time with a transplant was the same as among White patients. Increasing kidney transplant rates and improving allograft survival for Black children and young adults has the potential to help close the survival gap.

Background
The role of kidney transplantation in differential survival in Black and White patients with childhood-onset kidney failure is unexplored.

Methods
We analyzed 30-year cohort data of children beginning RRT before 18 years of age between January 1980 and December 2017 (n=28,337) in the US Renal Data System. Cox regression identified transplant factors associated with survival by race. The survival mediational g-formula estimated the excess mortality among Black patients that could be eliminated if an intervention equalized their time with a transplant to that of White patients.

Results
Black children comprised 24% of the cohort and their crude 30-year survival was 39% compared with 57% for White children (log rank P<0.001). Black children had 45% higher risk of death (adjusted hazard ratio [aHR], 1.45; 95% confidence interval [95% CI], 1.36 to 1.54), 31% lower incidence of first transplant (aHR, 0.69; 95% CI, 0.67 to 0.72), and 39% lower incidence of second transplant (aHR, 0.61; 95% CI, 0.57 to 0.65). Children and young adults are likely to require multiple transplants, yet even after their first transplant, Black patients had 11% fewer total transplants (adjusted incidence rate ratio [aIRR], 0.89; 95% CI, 0.86 to 0.92). In Black patients, grafts failed earlier after first and second transplants. Overall, Black patients spent 24% less of their RRT time with a transplant than did White patients (aIRR, 0.76; 95% CI, 0.74 to 0.78). Transplantation compared with dialysis strongly protected against death (aHR, 0.28; 95% CI, 0.16 to 0.48) by time-varying analysis. Mediation analyses estimated that equalizing transplant duration could prevent 35% (P<0.001) of excess deaths in Black patients.

Conclusions
Equalizing time with a functioning transplant for Black patients may equalize survival of childhood-onset ESKD with White patients.