Study Suggests Racial Role in Kidney Transplants
By Michael Smith, North American Correspondent, MedPage Today|
Published: February 10, 2012
· Note that racial disparities in access to renal transplantation have been known to exist, but the specific mechanisms which account for the effects of race and socioeconomic status have not been specifically delineiated.
· Point out tht this study at a single transplant center suggests that improving access to healthcare may reduce some, but not all, of the racial disparities in access to kidney transplantation.
Black patients with end stage renal disease (ESRD) had a 59% lower rate of kidney transplant than whites in one southeastern center, researchers reported.
An analysis of more than 2,200 patients treated at the Emory Transplant Center showed marked racial disparities in access to referral, transplant evaluation, waitlisting, and eventual transplant, according to Rachel Patzer, PhD, of Emory University in Atlanta, and colleagues.
Clinical, demographic, and socioeconomic factors explained only about 51% of the overall differences and what causes the rest remains unclear, Patzer and colleagues reported in the February issue of the American Journal of Transplantation.
The researchers cautioned that the findings might not reflect wider issues, since they are based on a single center where racial disparities might be more pronounced.
In their study, they noted, black patients formed 56% of the waiting list but only 44% of those who eventually got a transplant. But national data show blacks get a transplant at a rate nearly equivalent to their waiting list proportion, the researchers said.
Nonetheless, they concluded, the findings suggest that there are unknown barriers to equitable access to transplant.
The researchers analyzed records from the Emory Transplant Center, as well as those from the United States Renal Data System and the United Network for Organ Sharing, for 2,291 patients referred for evaluation from 2005 to 2007, with follow-up through May, 2010.
Of those, 64.9% were black, 57.3% were male, 33.6% lived in impoverished communities, and 16.1% had no health insurance coverage, Patzer and colleagues reported.
A multivariate analysis, taking into account clinical, demographic, and socioeconomic factors, found that the hazard ratio for transplant for blacks, compared with whites, was 0.41, with a 95% confidence interval from 0.28 to 0.58.
Demographic and clinical factors explained 20.8% of the reduced transplant rate among blacks, Patzer and colleagues reported, while individual and neighborhood socioeconomic factors explained 30.6%.
Among other findings:
· After referral, 51.5% of blacks began the evaluation process, compared with 60.6% of whites ( P<0.001).
· There was no significant difference in the proportion completing evaluation.
· 71% of whites were put on the waiting list for a deceased donor transplant and 30% got a new organ, compared with 59.6% and 18.1% of blacks (P<0.001).
There were also marked disparities in how long it took to progress through some of the steps to transplant, Patzer and colleagues found.
For instance, for blacks, the median time from the diagnosis of ESRD to referral was 283 days, compared with 84 for whites (P<0.001).
And blacks spent nearly a year longer on the waiting list for an organ - 727 days compared with 374 days for whites (P<0.001).
The study had support from the Emory University Race and Difference Initiative. The authors said they had no conflicts, the journal reported.
Primary source: American Journal of Transplantation
Patzer RE, etal. "The role of race and poverty on steps to kidney transplantation in the southeastern United States" American Journal of Transplantation 2012; 12: 358-368.
Study population characteristics
Among the 2291 adult (> 18 years) incident ESRD patients referred for transplant, the mean age at ESRD start was 49.4 ± 13.9 years, 64.9% were black, 57.3% were male, 33.6% lived in impoverished communities and 16.1% had no health insurance coverage (Table 1). Compared to whites, a greater proportion of black patients were younger (47.4 years vs. 53.1 years), female (45.3% vs. 38.0%) and had hypertension as the primary cause of ESRD (37.2% vs. 20.3%, p < 0.005). Black patients had reduced prevalence of cardiovascular disease (38.9% vs. 45.8%, p = 0.0013) compared to whites. In addition, blacks were more likely to have lower serum albumin (<3.5 g/dL), lower hemoglobin (<10 g/dL) and lower predialysis ESA use than whites (p<0.01 for all comparisons).
Racial differences in access to renal transplant steps
Among all patients eligible to progress to the next transplant step, a greater proportion of white versus black patients proceeded in starting the evaluation, waitlisting and receiving a transplant (p < 0.05), but no significant racial differences were observed in evaluation completion. Figure 2, panel A shows the racial differences in access to each transplant step among those who completed the prior step.
Among the 2291 patients referred to the ETC, only 54.7% of patients came to the first evaluation appointment. A greater proportion of black versus white patients did not start the evaluation (48.5% vs. 39.4%, p < 0.0001). Most (91.3%) patients completed the standard requirements for the transplant evaluation. Reasons for not completing the evaluation were comparable among racial groups with the exception of Òincomplete evaluation requirementsÓ, where black patients were significantly more likely to have incomplete requirements than white patients (45.7% vs. 17.9%) and have psychosocial reasons reported as a reason for not completing the evaluation process (10.0% vs. 0%) (Figure 1; p < 0.0001 for both comparisons).
A total of 733 patients (64.1% of patients who completed the standard evaluation requirements) were placed on the deceased donor waiting list. Among those waitlisted, 414 (56.4%) were inactive at some point during follow-up, with a median time inactive of 260 days (interquartile range [IQR]: 72, 585). Among those inactive, nearly half (46.8%) were first listed as inactive, with an additional 28.2% of patients inactive at some time after active listing (Figure 1). A greater proportion of inactive patients were black (68.1%) than white (40.8%) (p = 0.0283). Among all listed patients, 177 (24.1%) received a deceased donor transplant during the study period.
Racial differences in the duration of time patients remained in each transplant step were also observed (Figure 2, panel B). The overall median time from transplant referral to deceased donor transplant was 743 days (IQR: 453, 977) for whites and 1,096 days (IQR: 741, 1385) for black patients. The greatest racial differences were observed from ESRD start to referral and once a patient was placed on the waiting list (Figure 2, panel B).
Role of SES in racial differences to transplant access
Socioeconomic differences by race were also observed. For example, 19.2% of blacks and 10.3% of whites had no health insurance at the time of dialysis initiation, and black ESRD patients were twofold more likely to live in poor neighborhoods compared to white patients (Table 1; p < 0.0001 for both comparisons). Of those who did not have health insurance at the start of ESRD, the mean age was 41.8 years, the majority (77.6%) were black and 42.1% lived in neighborhoods where >20% of the census tract lived below the federal poverty line (data not shown).
SES measures for insurance, education, employment, distance, neighborhood poverty and degree of rurality were independently associated with completing several transplant steps, and there was a general trend of higher SES at each progressive step of the transplant process. For example, 43.8% of referred patients had private insurance (Table 1), but this increased to 56.8% of those who started the evaluation, 57.9% of those who completed the evaluation, 69.4% of those waitlisted and 74.0% of those who received a transplant (Table 2).
In multivariable Cox models, we found no statistically or clinically significant interactions between race and any SES measure. Table 3 shows the multivariable sequential modeling results. Overall, demographic and clinical factors explained 20.8% of the reduced transplant rate among blacks versus whites, and individual and neighborhood SES factors explained 30.6%. The degree to which demographic, clinical and SES factors explained racial disparities varied at each transplant step. SES factors accounted for 26.9% and demographic and clinical factors 16.4% of the lower rate of referral among blacks versus whites, but accounted for little to none of the disparities observed in the rate of starting the transplant evaluation once referred. Once waitlisted, clinical, demographic and clinical factors explained more than half (55.8%) of the reduced transplant rate among black versus white patients, and clinical and demographic factors (38.4%) explained a greater fraction of the disparity than SES factors (30.4%). However, large racial differences persisted even after adjustment for clinical, demographic and SES factors (Table 3).
Black ESRD patients evaluated at a large transplant center in the Southeastern United States have reduced access to renal transplantation, where black patients are 59% less likely to receive a transplant at any given time compared to white patients. Individual- and neighborhood-level SES factors explained 30.6% of the reduced rate of transplant among black versus white patients, but substantial racial disparities persisted in several steps of the renal transplant process even after accounting for demographic, clinical and SES factors, particularly in referral for transplant and the rate of transplantation among waitlisted patients. The results of this study suggest that improving access to healthcare may reduce some, but not all of the racial disparities observed in access to kidney transplantation.
Previous studies have also documented racial disparities in access to transplant referral and evaluation completion. In a study of dialysis patients in Indiana, Kentucky and Ohio, Alexander et al. (8) reported that black patients were less likely to be interested in transplant, complete the pretransplant workup and move up a waiting list compared to white patients. Other studies have reported that blacks complete the transplant evaluation process slower (11) and are less likely to be rated as appropriate candidates for transplant even after evaluation compared to white patients (12).
The disparities observed between racial and ethnic groups are not entirely explained by clinical or biologic factors, and SES has been hypothesized to play a role (8,24,25). Schold et al. recently reported that racial disparities observed in a population of patients referred for renal transplantation in Florida are largely explained by SES, as measured by health insurance and county income (26). In contrast, Hall et al. reported that racial disparities in access to waitlisting were somewhat attenuated after adjusting for SES, where health insurance coverage and zip code poverty explained 21% of the reduced rate of waitlisting among black patients in the United States. However, once a patient was waitlisted, SES accounted for little if any of the racial disparities (1). Similarly, in our study, SES as measured by more sensitive SES measures accounted for 30.6% of the reduced rate of transplant but SES did not entirely explain the racial disparity observed in access to renal transplant. Additionally, even though black patients in our study had lower SES on average, the racial disparity in transplant access was consistent across levels of SES.
There are several potential explanations why racial disparities that are unexplained by demographic, clinical and SES factors measured in this study exist in early steps of the renal transplant process. Racial bias may partially explain why black patients have reduced access to transplant compared to white patients (3,27,28). Klassen et al. examined the role of racial discrimination among adult renal transplant eligible patients in hemodialysis centers in Baltimore, finding that patients who reported a lifetime experience of racial discrimination experienced reduced access to waitlisting (29). Variations in referral for transplant at the referring provider or dialysis facility level may also account for the observed racial differences. Prior research suggests that a small number of providers may account for the racial differences in the quality of patient care (30,31). Limited access to healthcare may disproportionately affect minority patients (3) and if not adequately measured, could explain some of the observed racial disparity. In a recent study, Prakash et al. found that as the percentage of black patients in a neighborhood increases, the likelihood of access to pre-ESRD nephrology care decreases (32). Compared to whites, black ESRD patients in our study population were more likely to lack insurance coverage, have a lower prevalence of predialysis ESA use, and more anemia and hypoalbuminemia at incident ESRD, all of which are proxies for early access to healthcare and may portend poorer health status at time of referral for evaluation. We also used neighborhood poverty, degree of rurality and distance to transplant center as proxies for access to care, but perhaps better measures of healthcare quality and accessibility could explain some of the observed racial differences in access to kidney transplantation.
Our study has several strengths. The racial distribution of our study (61% black) provides us with ample study power to examine racial differences in access to each step of the renal transplant process. Follow-up data for this analysis was validated using USRDS-linked with UNOS data to capture virtually all waitlist and transplant outcomes, thus limiting selection bias due to loss to follow-up. We assessed SES using both individual- and neighborhood-level measures, which permitted the evaluation of poverty in a multilevel framework. The use of census data to estimate neighborhood SES, as opposed to zip code data, is more sensitive (33). National studies that examine access to the deceased donor waitlist and transplant receipt typically include all dialysis patients, even though some may have medical comorbidities that preclude them from transplantation (9). Since 30% of dialysis patients may be medically ineligible for renal transplantation, an examination of racial disparities among referred patients is preferred (29). We examined the proportion of patients progressing to each step based on the number of patients completing the prior step, rather than including all dialysis patients.
Limitations to our study should be noted. Our study was conducted at a single transplant center and results may not be generalizable to all ESRD patients. For example, the racial disparities observed in the Southeast may be more pronounced. In our study, which took place over a median follow-up of nearly 4 years, black patients comprised 56% of the waiting list but only represented 44% of those transplanted. However, on a national level, blacks received 33.4% of all deceased donor transplants, nearly equivalent to their waiting list proportion (34.1%) (34). At this time, the assessment of factors which impact transplant referral and evaluation are not captured in national surveillance databases but these data are important to better understand disparities in the continuum of the transplant process in other regions throughout the United States. Regional and geographic differences between the Southeast and other regions may also limit generalizability of these findings, such as differences in care for ESRD patients (35), average transplant waiting times (36), or transplant center characteristics (37).
Although our study adjusted for demographic, clinical and SES factors, there may be unmeasured factors unaccounted for in our analyses, such as changes in health status. Information on the reasons a patient had incomplete evaluation requirements or inactive waitlisting was not available in our study and could explain part of the observed racial disparity. This study was retrospective in nature and the causal pathway between SES and racial disparities cannot be discerned. In addition, the source population of ESRD patients eligible for transplant in this study is not known. Our results may underestimate racial disparities if the rate of referral is higher among whites versus blacks. Additionally, we were unable to determine if dialysis facility factors contributed to the observed racial disparities; it would be helpful to collect national data on referral and evaluation rates by dialysis facility to identify center practice variations and target interventions to improve equitable access to transplant.
To our knowledge, this is the first study to examine race and both individual- and census tract-level SES in access to each step of the renal transplant process. We found that racial disparities are evident in several steps of the renal transplant process, and that while SES explained some of the racial differences, black patients had a 59% lower rate of transplant than white patients even after accounting for demographic, clinical and SES factors. This suggests that improving access to care for patients may help reduce some, but not all, of the racial disparities in access to transplant. Efforts to improve equity in access to renal transplantation may need to focus on earlier steps of transplant access, in addition to the waitlisted population.