Abstract
Background and objectives Pre-ESRD care is an important predictor of outcomes in patients undergoing long-term dialysis. This study examined the extent of variation in receiving pre-ESRD care and black-white disparities across urban and rural counties.
Design, setting, participants, & measurements Participants were 404,622 non-Hispanic white and black patients aged >18 years who began dialysis between 2005 and 2010 and resided in 3076 counties from the U.S. Renal Data System. The counties were grouped into large metropolitan, medium/small metropolitan, suburban, and rural counties. Pre-ESRD care indicators included receipt of nephrologist care at least 6 or 12 months before ESRD, dietitian care, use of arteriovenous fistula at first outpatient dialysis session, and use of erythropoiesis-stimulating agents (ESAs) in patients with hemoglobin level < 10 g/dl.
Results Large metropolitan and rural counties had lower percentages of patients who received pre-ESRD nephrologist care (25.7% and 26.9% for nephrologist care > 12 months), compared with the higher percentage in medium/small metropolitan counties (31.6%; both P<0.001). For both races, nonmetropolitan patients had poorer access to dietitian care and lower ESA use than metropolitan patients. Consistently in all four geographic areas, black patients received less care than their white counterparts. The unadjusted odds ratios of black versus white patients in receiving nephrologist care for >12 months before ESRD were 0.66 (95% confidence interval [CI], 0.61–0.72) in large metropolitan counties and 0.79 (95% CI, 0.69–0.90) in rural counties. The patterns remained, albeit attenuated, after adjustment for patient factors.
Conclusions The receipt of pre-ESRD care, with blacks receiving less care, varies among geographic areas defined by urban/rural characteristics.
Introduction
Pre-ESRD care from specialists, including nephrologists and dietitians, is important for optimizing clinical outcomes for patients with advanced CKD. Timely receipt of nephrologist care is associated with slower CKD progression, lower rates of adverse outcomes, and improved quality of life (1–15). For patients with advanced CKD, nephrologist care increases the likelihood of receiving kidney transplantation or initiating maintenance dialysis with a functional arteriovenous fistula (AVF) (16–18). Recent studies have also demonstrated that timely nephrologist care is cost-effective (19,20). Hence, practice guidelines recommend that all patients in stage 4 and 5 CKD should be under nephrologist care (21,22). However, 25%–50% of patients undergoing maintenance dialysis in the United States had not received any pre-ESRD nephrologist care (23).
Although geographic variation in access to pre-ESRD care and less care received by black patients have been noted (7,15,24–27), little is known about differences between urban and rural areas at a national level. The Agency for Healthcare Research and Quality 2010 report demonstrates that residents of nonmetropolitan areas were less likely than their urban counterparts to receive recommended preventive services in the general population (28).
We conducted a national population analysis to examine the associations between race and geographic area and quality-of-care indicators in patients approaching ESRD. We grouped counties in the United States into four categories: large metropolitan, medium/small metropolitan, suburban, and rural. The specific purposes were to (1) assess whether the receipt of pre-ESRD care differs among the four county categories and (2) assess whether there is a certain county category where the black-white difference in receiving pre-ESRD care is particularly large and, if so, to determine whether the difference persists after accounting for various aspects of patient characteristics.
Materials and Methods
Data Sources
We used two data sources: the U.S. Renal Data System (USRDS) (23) and Area Resource Files, an integrated database that contains county attributes for all counties in the United States (29). The revised 2005 Centers for Medicare & Medicaid Services (CMS) ESRD Medical Evidence Report included information on pre-ESRD care that patients had received before initiation of renal replacement therapy. These data on pre-ESRD care include nephrologist care, dietitian care, native AVF (the preferred type of vascular access for hemodialysis) at first outpatient dialysis session, and the use of erythropoiesis-stimulating agents (ESAs). We obtained these data, along with patient covariates including the residential county, from the USRDS.
Study Population
We identified all patients who had newly begun maintenance dialysis, had completed the revised Medical Evidence form between 2005 and 2010, were black or white, were 18 years of age or older at the initiation of dialysis, had not previously undergone kidney transplantation, and resided in any of the 50 states or the District of Columbia. We excluded Hispanic patients in order to achieve a more homogeneous non-Hispanic white population, as well as patients whose residential counties cannot be linked to the Area Resource Files. We excluded patients (11.6%) for whom information on pre-ESRD nephrologist care was missing. The final study cohort includes 404,622 non-Hispanic black or non-Hispanic white patients who resided in 3076 counties. Compared with the patients in the cohort, those excluded because of unavailable information on nephrologist care were slightly older (64.7 versus 63.8 years), were more likely to be black (40.0% versus 34.1%), were less likely to be hypertensive (79.2% versus 85.1%), were current smokers (5.2% versus 7.4%), or had atherosclerotic heart disease (15.5% versus 23.3%) or peripheral vascular disease (11.5% versus 14.9%). Otherwise, there were no major differences in known factors, including sex and diabetes (data not shown). The study was approved by the Institutional Review Board for Health Sciences Research at the University of Virginia.
Urban/Rural County Categories
We used the Rural-Urban Continuum Codes developed by the U.S. Department of Agriculture in 2003 (30). The first three of the nine codes define the three categories of metropolitan counties by the population size of their metropolitan areas, and the other six codes define the six categories of nonmetropolitan counties by the degree of urbanization and adjacency to metropolitan areas (Supplemental Table 1). According to this scheme, we grouped 3076 counties into four categories: large metropolitan counties (situated in metropolitan areas with ≥1 million people; code 1); medium/small metropolitan counties (in metropolitan areas with <1 million people; codes 2 and 3); suburban counties (nonmetropolitan counties adjacent to metropolitan areas; codes 4, 6, 8); and rural counties (nonmetropolitan counties and not adjacent to metropolitan areas; codes 5, 7, 9). We obtained these codes from the Area Resource Files (29).
Pre-ESRD Care Indicators
We examined five care indicators. The first two were whether patients had received care by a nephrologist at least 6 months or 12 months before ESRD. Three other pre-ESRD care indicators were assessed in the group of patients who had seen a nephrologist: (1) whether the patient had received dietitian care, (2) whether a patient with a hemoglobin level <10 g/dl had received ESAs, and (3) whether the patient had an AVF used for the first outpatient dialysis session. It should be noted that the administration of ESAs for patients with CKD who had a hemoglobin level <10 g/dl was the standard of care in the era of this study.
Patient Covariates in Adjusted Analyses
Patient race (African American/black or Caucasian/white) and ethnicity (Hispanic or non-Hispanic) were classified in the CMS Medical Evidence form. In the adjusted analysis, 26 patient factors extracted from the Medical Evidence form were grouped and sequentially added to the models: (1) sex, race, and age at ESRD onset; (2) 21 other clinical factors reflecting lifestyle behaviors (smoking, alcohol dependence, drug dependence), physical/functional conditions, and multiple comorbid conditions (e.g., diabetes, hypertension, various cardiovascular diseases, and cancer); and (3) employment status (employed/unemployed) at 6 months before ESRD and health insurance at ESRD onset. Each patient’s health insurance status was assigned to one of the following 10 categories: no insurance, four categories of single insurance (Medicaid, Medicare, employer-group, other), four categories of insurance coverage by two agencies (Medicaid plus Medicare, Medicaid plus one other non-Medicare, Medicare plus one other non-Medicaid, any two of non-Medicare and non-Medicaid), and insurance coverage by three or more agencies.
County Variables
County characteristics were described in percentage of persons who completed high school, percentage of persons in poverty, percentage of black population, percentage of persons without health insurance, and population density. We also obtained several other variables that represent county health care resources, including total numbers of hospitals, physicians, and nephrologists (31), as well as corresponding numbers per county population.
Statistical Analyses
We assessed the association between urban/rural residence and pre-ESRD quality of care by comparing the percentage of patients who received care across county categories. We first examined the unadjusted results, then results adjusted sequentially for demographic characteristics alone, 21 additional clinical factors, and employment and health insurance categories. Marginal logistic regression using generalized estimating equations was used to examine the association for each care indicator. Confidence intervals and P values were computed using empirical (sandwich) standard errors that incorporated intracounty correlations (32). Analyses were performed using SAS procedure GENMOD (SAS Institute Inc., Cary, NC).
We assessed the black-white differences in the likelihood of receiving pre-ESRD care within each county category. We performed several stratified analyses by county category, each adjusted for various patient factors. Statistical interactions between race and county category in receiving care were examined.
Results
Patient and County Characteristics
Of 404,622 patients, 203,778 (50.3%) resided in 412 large metropolitan counties, 121,323 (30.0%) in 675 medium/small metropolitan counties, 54,602 (13.5%) in 1049 suburban counties, and 24,919 (6.2%) in 940 rural counties (Table 1). Compared with patients in metropolitan counties, those living in suburban and rural counties were less likely to be black, were more likely to be smokers and employed, had more comorbid conditions, and were more limited in mobility and functionality. The percentages of patients with employer-group carrier were substantially lower in suburban and rural counties.
Characteristics of patients and counties by county category
Compared with metropolitan counties, rural and suburban counties were on average poorer, had lower percentages of blacks and high school graduates, and had a higher percentage of people without insurance (Table 1). Notably, health care resources were substantially lower in rural and suburban areas than in metropolitan counties. For example, the number of nephrologists, adjusted for county population, in large metropolitan or medium/small metropolitan counties was more than three times that in suburban or rural areas (18.2 or 19.2 versus 5.1 or 3.9 per 1 million persons).
Pre-ESRD Care by County Category and Race
Across the four-county categories, the percentage of patients who received pre-ESRD nephrologist care for >6 or 12 months was lowest in large metropolitan (50.1% or 25.7%, respectively) and rural (51.6% [P=0.21] or 26.9% [P=0.23]) counties, was intermediate in suburban counties (53.1% [P=0.009] or 27.9% [P=0.02]), and highest in medium/small metropolitan counties (56.6% [P<0.001] or 31.6% [P<0.001]) (all P values compared with large metropolitan counties). Among all patients who received nephrologist care, only 17.9% had seen a dietitian, ranging from 15% in suburban and rural counties to 19.5% in large metropolitan counties (P<0.001). Similarly, prevalence of ESA use among those who saw a nephrologist when their hemoglobin level decreased to <10 g/dl was also lower in suburban (47.2%; P<0.001) and rural (50.2%; P=0.005) counties than in metropolitan counties (53.4%). Prevalence of AVF was similar across the four areas (22%) (Table 2).
The receipt of pre-ESRD care across urban and rural county categories
In both races, access to nephrologist care was better in medium/small metropolitan and suburban counties than in large metropolitan and rural counties (Figure 1A). After receipt of care by a nephrologist, for both races, access to dietitian care and receipt of ESAs were consistently better in metropolitan counties than in nonmetropolitan counties (Figure 1, B and C). For all these care measures, black patients were less likely to have received care than were whites in all four county categories (Figure 1). This disparity was more pronounced in large metropolitan and rural counties for nephrologist care (interaction P<0.001), in suburban and rural counties for dietitian care (interaction P<0.001), and in suburban counties for AVF (interaction P=0.01) (Figure 1 and Table 3). Furthermore, the patterns of the racial disparity level across the four geographic areas appeared to be consistent for ESAs and AVF, with the largest disparity in suburban counties, whereas for dietitian care the disparity increased as the area approached more rural (Figure 1).
Unadjusted percentages and 95% confidence intervals of patients who received pre-ESRD care in large metropolitan, medium/small metropolitan, suburban, and rural counties. (A) Receipt of nephrologist care for >6 months before initiation of maintenance dialysis. (B) Receipt of pre-ESRD dietitian care among patients who saw a nephrologist before ESRD. (C) Receipt of erythropoietin-stimulating agents (ESAs) in patients who saw a nephrologist and had hemoglobin level <10 g/dl. (D) Use of arteriovenous fistula (AVF) for first outpatient dialysis session among patients who saw a nephrologist before ESRD. The horizontal dotted and dashed lines are the average values for white and black patients, respectively.
Racial differences in receiving pre-ESRD care stratified by county category
Adjusted Analyses
After adjustment for various patient factors, the overall patterns described above were largely unchanged and significant differences across county categories remained for most care indicators (Table 2). For example, in comparing nephrologist care for >6 months between medium/small metropolitan counties and large metropolitan counties, odds ratio of 1.30 (95% confidence interval [CI], 1.19–1.43) reduced just slightly to 1.26 (95% CI, 1.16–1.38) after the adjustments while remaining highly significant (both P<0.001). These results indicate that the difference in pre-ESRD care across urban and rural areas was unlikely to be attributable to the difference in patient characteristics.
The racial difference in receiving care was also evaluated for each county category adjusted for patient factors. In all four county areas, there appeared to be a large, consistent attenuation of the black-white odds ratios for receiving early nephrologist care (>12 months) and ESAs after adjustment for employment and health insurance (Table 3). For example, the unadjusted odds ratio of black patients versus white patients in pre-ESRD nephrologist care for >12 months in suburban counties was 0.86 (95% CI, 0.79–0.93); this was attenuated slightly to 0.87 (95% CI, 0.80–0.94) after adjustment for demographic and clinical factors and was attenuated greatly to 0.97 (95% CI, 0.89–1.05) after additional adjustment for employment and health insurance.
Discussion
Most research on disparity of health care for patients with CKD or ESRD has focused on patient and provider levels, but the role of geography or residential place has only recently received attention. One recent study reported that patients living in residential areas with a larger proportion of black residents were less likely than those in other areas to have received nephrologist care (26). Another study found that county poverty is associated with the decreased likelihood of AVF use (33). To our knowledge, our study is the first to examine combined urbanization/rurality and racial/ethnic variations in pre-ESRD care at a national level. It has been well established through the extensive literature published by the Dartmouth Institute group (34–36) that “geography determines medical destiny” in regard to the quality of and access to care. Because pre-ESRD care may influence late CKD and ESRD survival, a better understanding of this notion in pre-ESRD care is an important step toward a more public health–oriented understanding of late CKD and ESRD care. In this study, several significant findings have important clinical and public policy implications.
A major finding is the significant differences in receiving pre-ESRD care across the four-county categories. We found poorer access to nephrologist care in large metropolitan areas, similar to a prior study that reported poorer access to usual source of care in large metropolitan areas (37). The reasons for the greatest disadvantage of black patients in access to nephrologist care in large metropolitan and rural counties were multifactorial but were most likely related to their general low socioeconomic status (SES). Rural black patients were more likely to be of low SES and may live in isolated rural areas with no nephrologist nearby. They may need to travel long distances in order to see a specialist, and there is often no public transportation in rural areas, further contributing to the increased likelihood of delays in receiving specialist care. By contrast, urban black patients with low SES may have unique challenges related to safety and transportation that may create functional islands of “health care deserts.”
We found that after the receipt of care by a nephrologist, patients of both races received less dietitian care and ESA use in nonmetropolitan residence than in metropolitan residence. This finding is consistent with the recent Agency for Healthcare Research and Quality report that rural residents were less likely than their urban counterparts to receive recommended preventive services and made fewer visits to health care providers (28). However, the likelihood of ESA and AVF use was consistently lower among black patients compared with white patients in all four county categories (Figure 1, C and D), suggesting that some common factors might have contributed to the disparities. One possible explanation may be differences in clinical practices between nephrologists seeing black patients and those seeing white patients, consistent with prior studies showing that even within the same geographic area, black and white patients tend to see different health care providers (38). Our findings for these three care measures (dietitian, AVF, ESA) were drawn from the subgroups of patients who had seen a nephrologist before ESRD, which allows for better study of the possible causes with the effect of the disparate access to pre-ESRD nephrologist care removed. When all patients were included, the patterns for the associations of urban/rural residence and these measures were largely consistent with the pattern for nephrologist care.
Another interesting finding was the increasing racial disparity in pre-ESRD dietitian care as the area became more rural (Figure 1B). A potential explanation is that rural black patients with low SES were more likely to live in economic deprived rural areas where there is no dietitian. In addition, within these deprived rural areas, black patients tend to be more disadvantaged than whites in competing for the limited resources because of their lower SES.
We found that patients’ ability to access health care in general was an important determinant for the lower likelihood of blacks’ receiving pre-ESRD care. The large, consistent attenuation of the black-white differences in receipt of early nephrology care and ESA use but not the other measures after adjustment for employment and health insurance might reflect higher-quality care, which could represent a stronger determinant of downstream ESRD outcomes (transplantation, hospitalization, mortality). Of note, after adjustment for various patient factors, there were still significant racial/ethnic differences in receipt of pre-ESRD care, suggesting that additional strategies will be needed to understand and address these findings.
These findings have limitations. Pre-ESRD care may have been misreported. Kim et al. (39) recently examined the agreement between predialysis nephrology care reported on the CMS Medical Evidence form with that reported on CMS claims. Although the degree of agreement varied depending on the indicators, there were great consistencies for the indicators used in the present study (86%–89% for nephrologist care for >6 months and 72%–75% for nephrologist care for >12 months). Further, our findings of poorer access to pre-ESRD care in rural areas are consistent with those of other studies reporting poorer access to preventive care and cancer care in rural areas (28). Second, we limited our analyses to the care-process measures as well as the covariates that are available at the national ESRD population. Our multivariate models did not adjust for other patient variables, including SES (income and education attainment), health beliefs, and behaviors, because they were not available. Numerous studies have used neighborhood SES as a proxy (40). Because this substitution could have introduced some other unobserved bias, we have elected not to use this approach before its validity is carefully assessed. In an attempt to minimize the bias, we categorized insurance coverage into the 10 categories to best capture SES information underlying health insurance status. Third, our exclusion of patients with missing data on pre-ESRD care may have biased the results. Fourth, data on other important aspects of care, such as bone disease related to CKD and some care processes related to controlling of CKD progression and cardiovascular risks, are not available for analysis. Finally, our analyses were limited to access to care specifically provided by nephrologists and not by other practitioners who may also make significant contributions to clinical care. Assessing individual practitioners’ attributes would be a very challenging task.
In summary, we present the first study that assessed pre-ESRD care processes on the basis of urban-rural characterization of counties. The results show highly variable pre-ESRD care measures among different urban/rural categories and their interactions with race, highlighting complexity of the issue that may explain in part the limited progress in improving racial/ethnic disparities in CKD/ESRD care processes and outcomes. These findings suggest improving receipt of key pre-ESRD indicators will require more refined regional characterization of health care needs and working with renal and renal dietitian organizations around employment opportunities for new graduates. Our findings illustrate the point that health care polices directed at eliminating pre-ESRD care disparities must consider these complexities and granular data.
Disclosures
None.
Acknowledgments
The authors thank staff at the USRDS for their assistance in providing the USRDS data.
This work is funded by National Institutes of Health (NIH)/National Institute of Diabetes and Digestive and Kidney Disease 5R01DK084200-02. In addition, K.N. is supported in part by NIH grants U54MD007598, UL1TR000124, P30AG021684, and P20-MD000182. The content is solely the responsibility of the authors and does not necessarily represent the official views of the NIH.
Footnotes
Published online ahead of print. Publication date available at www.cjasn.org.
This article contains supplemental material online at http://cjasn.asnjournals.org/lookup/suppl/doi:10.2215/CJN.07780812/-/DCSupplemental.
See related editorial, “Making the Crooked Way Straight: Interpreting Geography and Health Care Delivery in CKD,” on pages 518–519.
- Received August 1, 2012.
- Accepted November 14, 2012.
- Copyright © 2013 by the American Society of Nephrology
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