Kidney Transplant Linked to Lower Mortality Risk in Sickle Cell Patients

Sunjae Bae, PhD, MPH

Findings from a new study indicate that a decrease in mortality following kidney transplantation among patients with sickle cell-related kidney failure was comparable with those of other kidney failure causes.

The study also revealed that the sickle cell population was less likely to receive a kidney transplant despite waitlist registration.

Led by Sunjae Bae, PhD, MPH, Division of Transplantation, Department of Surgery, Johns Hopkins School of Medicine, the investigative team used the United States Renal Disease System (USRDS) and the Scientific Registry of Transplant Recipients (SRTR) to evaluate adults with kidney failure who began maintenance dialysis or were put on a waitlist.

Their study quantified the decrease in mortality associated with kidney transplantation as well as determined the chance of receiving the operation among patients with sickle cell disease.

“Patients with sickle cell disease–associated kidney failure have high mortality, which might be lowered by kidney transplantation,” wrote Bae and colleagues.

“However, because they show higher post-transplant mortality compared with patients with other kidney failure etiologies, kidney transplantation remains controversial in this population, potentially limiting their chance of receiving transplantation.”

Kidney Transplantation, Mortality, and Access

The investigators compared mortality risk between sickle cell kidney transplant recipients with non-sickle cell recipients — risk was then compared with matched individuals on a transplant waitlist.

Thus, among 507 kidney transplantation waitlist candidates with sickle cell disease, 192 patients received a transplant.

Among 483,298 waitlist candidates without sickle cell disease, 243,045 went on to receive a kidney transplant.

The investigators excluded 3 sickle cell recipients and 2 control recipients who could not be matched to waitlist patients.

“Compared with their matched waitlisted candidates, 189 transplant recipients with sickle cell disease and 220,251 control recipients showed significantly lower mortality,” wrote the investigators.

They noted that the absolute risk difference at 10 years post-transplant was 20.3 (98.75% CI, 0.9-39.8) percentage points for the sickle cell group and 19.8 (98.75% CI, 19.2-20.4) percentage points for the control group. These improvements were also noted for 1 year, 3 years, and 5 years post-transplant.

Furthermore, the team reported that the hazard ratio was similar between the sickle cell kidney recipients (0.57; 95% confidence interval, 0.36 to 0.91) and control recipients (0.54; 95% CI 0.53-0.55; P = 50.8).

And finally, Bae and team found that the sickle cell group had lower access to transplantation. As such, patients starting dialysis initiation were less likely to receive a kidney transplantation than controls (subdistribution HR, 0.73; 95% CI, 0.61-0.87).

Similar disparities were also noted among waitlisted candidates (HR, 0.62; 95% CI, 0.53-0.72).

Conclusion

The investigators nonetheless acknowledged that mortality among sickle cell patients post-transplantation remained higher compared with controls (10 year, 50% versus 32%). However, they reiterated the decrease in mortality was similar between both groups.

More concerning was the limited to access to transplantation for the sickle cell population.

“Given our observation of 3-fold post-transplant mortality in the sickle cell group [compared with controls—following adjustment for various clinical characteristics], performing kidney transplants on candidates with sickle cell disease will negatively affect the center’s aggregate mortality, well above the 185% threshold,” Bae and colleagues wrote.

“This feature is clearly a disincentive for transplant centers to perform kidney transplants on candidates with sickle cell disease,” they suggested.

Despite this, they encouraged efforts to improve access to transplantation within this already at-risk population.

The study, “Mortality and Access to Kidney Transplantation in Patients with Sickle Cell Disease–Associated Kidney Failure,” was published online in Clinical Journal of the American Society of Nephrology.