Long-term health outcomes have not been well defined among racially diverse living kidney donors. We used administrative insurance data that were collected in the course of actual practice to examine medical diagnoses among living kidney donors, independent of follow-up by the transplantation center. As compared with white donors, black and Hispanic donors had an increased risk of hypertension, drug-treated diabetes, and chronic kidney disease after nephrectomy than did white donors, increases that were not explained by socioeconomic factors. The absolute prevalence of diabetes in donors did not exceed that in the general population, but the prevalence of hypertension was higher than NHANES estimates in some subgroups. End-stage renal disease was reported in less than 1% of donors but was more common among black donors than among white donors. Thus, as in the general U.S. population,7–10
racial disparities in medical conditions appear to occur among kidney donors.
We found that black donors had an increased risk of hypertension, as compared with white donors, similar to racial disparities in the general population. The Amsterdam Forum’s medical guidelines for living kidney donors state that the presence of hypertension at the time of evaluation is a general exclusion to kidney donation, except in patients with hypertension whose condition is defined as “low risk.”22
According to the seminal Mayo Clinic study,23
white race is included among low-risk criteria. Recent data from predominantly white cohorts suggest that there is an increased risk of hypertension among donors, as compared with the general population, possibly due to physiological alterations (including hyperfiltration in the remaining kidney and changes in vascular tone and renin–angiotensin–aldosterone regulation) or heightened follow-up.24,25
Hypertension was recently identified in 41% of 39 black donors who were evaluated at an average of 7 years after nephrectomy at one center.26
In our study, the increased prevalence of hypertension among Hispanic donors, as compared with the general population, may, in part, reflect underreporting of hypertension in this ethnic group, as compared with white respondents, in NHANES. Other studies have reported decreased rates of hypertension among Hispanic persons, as compared with non-Hispanic white persons, on the basis of both self-reporting and measured blood pressure.8,27–30
Nonetheless, in our study, the prevalence of hypertension among Hispanic donors did not exceed that among black donors. We speculate that medical surveillance after kidney donation may mitigate barriers to the recognition of hypertension rather than differentially affect the risk of hypertension among Hispanic donors.
As in the general population, diabetes was more common among black and Hispanic donors, as compared with white donors. Canadian researchers recently found a substantially higher risk of diabetes after kidney donation among aboriginal donors than among white donors, mirroring the disparities in risk in the local population.31
However, in our study, the estimated prevalence of diabetes among black or Hispanic donors did not exceed the prevalence among corresponding subgroups in the general population. A diagnosis of diabetes at evaluation should preclude donation,22
and our data support the finding of a reduction in the absolute prevalence, although not the relative prevalence, of diabetes among black and Hispanic donors, probably as a result of donor-selection practices.
We observed that black and Hispanic donors had approximately twice the risk of chronic kidney disease as white donors. In NHANES, the prevalence of chronic kidney disease was also twice as high among black respondents as among white respondents and tended to be higher among Hispanic respondents than among white respondents. Similarly, the 2008 U.S. Renal Data System registry reported that the national incidence of end-stage renal disease among black persons was 3.7 times that among white persons, and end-stage renal disease among Hispanic persons was 1.5 times that among non-Hispanic white persons.32
Recent queries of registrations of kidney-transplant candidates showed that although 12% of living kidney donors during the period from 1996 through 2007 were black, black donors represented 43% of 148 previous donors who were subsequently listed for kidney transplantation.33,34
Our data also suggest that nonwhite donors have an increased frequency of end-stage renal disease, although the number of such events was low. We did not detect significant race-related differences in cardiovascular diagnoses.
Although we found evidence of socioeconomic disadvantage for nonwhite donors, the donor’s socioeconomic status did not correlate with the studied medical diagnoses. Since all donors had private health insurance during the observation period, it may be that possession of insurance attenuated health disparities that were based on socioeconomic status. In addition, our socioeconomic measure may have lacked precision, since we used neighborhood socioeconomic status as a surrogate for individual status. The exclusion of uninsured donors may have underestimated medical complications in nonwhite donors,35
since a lack of health insurance is more common among nonwhite donors than among white donors.36,37
Our study has inherent limitations, given the available data and sampling approach. Reasons for entry into and exit from the insurance plan are not available, and disenrollment related to events such as health status cannot be identified. Outcome measures that were available in the administrative data differed from those in the NHANES data. Billing claims have been shown to provide sensitive measures of diagnoses of diabetes and cardiovascular disease in other populations15,19
but probably underrepresent the burden of kidney dysfunction, as compared with laboratory-based measures.17
On the basis of claims data that may be left-censored for the absence of insurance benefits within the available data, we were unable to distinguish incident diagnoses definitively. The sub-analysis of the period during which the OPTN collected baseline data on hypertension suggests that some centers have allowed more potential white donors with elevated blood pressure at evaluation to proceed with donation, as compared with those of another race or ethnic group. This finding is consistent with limited data describing white race as a low-risk criterion for hypertension among potential donors.23
Yet despite the apparent exclusion of potential black kidney donors with reported hypertension at evaluation, black donors had an increased rate of hypertension after nephrectomy, as compared with white donors. It is possible that the evaluation and reporting of normal blood pressure from the donor-candidacy evaluation to OPTN vary across centers. The study data also lacked baseline information on body-mass index.
The stringency of living-donor selection has inherent tensions with the goal of increasing the organ supply. Black patients with end-stage renal disease have decreased access to transplantation, including living-donor allografts, as compared with white patients.38,39
As compared with white candidates for kidney transplantation, black candidates are less likely to identify potential living donors, and their potential living donors are less likely to donate for reasons including medical exclusion.40
Despite these exclusions from donation and the demonstrated benefit of selection for kidney donation in reducing the absolute risk of some health complications, such as diabetes, our data show that as in the general population, black kidney donors remain at increased relative risk for hypertension, diabetes, and chronic kidney disease, as compared with white donors. Race and ethnic group should not be used to discourage donor evaluation, but these data may increase awareness of variation in long-term outcomes among living donors and of the need for longer in-depth follow-up of demographically diverse living donors.