Racial and Ethnic Disparities in the Use of High-Volume Hospitals

Gray, Bradford H., Schlesinger, Mark, Siegfried, Shannon Mitchell, Horowitz, Emily, Inquiry

Differences in the source of care could contribute to racial and ethnic disparities in health status. This study looks at a major metropolitan area and examines racial and ethnic differences in the use of high-volume hospitals for 17 services for which there is a documented positive volume-outcome relationship. Focusing on the hospitalizations of New York City area residents in the periods 1995-1996 and 2001-2002, we found, after controlling for socioeconomic characteristics, insurance coverage, proximity of residence to a high-volume hospital, and paths to hospitalization, that minority patients were significantly less likely than whites to be treated at high-volume hospitals for most volume-sensitive services. The largest disparities were between blacks and whites for cancer surgeries and cardiovascular procedures.

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Although racial and ethnic disparities in health care and treatment outcomes have been extensively documented in the United States, the causes are poorly understood (Institute of Medicine 2002). Disparities persist even when data are adjusted for socioeconomic differences, health insurance status, and other access-related factors. Effective remedial policy depends on an understanding of the causes (Epstein 2004).

Disparities in the process or outcomes of treatment could result from a number of factors including being treated differently, a possibility that has prompted calls for improved "cultural competence" among providers, or receiving care from different providers whose abilities or practice styles vary. Several studies support the former scenario (Schulman et al. 1999; Balsa, McGuire, and Meredith 2005; Green et al. 2007), and there is considerable evidence of racial and ethnic differences in source of care. Minority patients tend to be treated by providers with different training (Bach et al. 2004; Educational Commission for Foreign Medical Graduates 1992) and in different settings than white patients (Lillie-Blanton, Martinez, and Salganicoff 2001; Bradley et al. 2004; Kahn et al. 1994; Birkmeyer et al. 2002; Rothenberg et al. 2004; Barnato et al. 2005; Groeneveld, Laufer, and Garber 2005; Skinner et al. 2005; Hasnain-Wynia et al. 2007; Jha et al. 2008).

A key question is whether the use of different providers has quality implications. Quality shortfalls have been documented among physicians treating more minority patients with regard to credentials, continuity of care, and timely referrals (Bach et al. 2004; Lillie-Blanton, Martinez, and Salganicoff 2001; Hargraves, Cunningham, and Hughes 2001; Mukamel, Murthy, and Weimer 2000). Evidence about racial differences in the quality of the source of hospital care is more mixed (Kahn et al. 1994; Rothenberg et al. 2004; Rask et al. 1994; Leape et al. 1999; Liu et al. 2006), and researchers have only begun to examine whether quality disadvantages may result from the use of different providers by minorities other than blacks (Liu et al. 2006).

This study addresses the extent and causes of racial and ethnic quality disparities in the source of care by examining patterns in the use of high-volume hospitals in the New York metropolitan area for 17 services for which a positive volume-outcome relationship has been documented in previous research. Liu et al. (2006) recently reported that such disparities exist for 10 complex surgical procedures in California, with minorities less likely than whites to use high-volume hospitals and more likely to use low-volume hospitals.

Our study complements the California study in several ways. First, we focus on a racially diverse geographic area in which the entire population lives relatively close to high-volume hospitals. Second, we examine a larger set of services than was examined in the California study, including both surgical and nonsurgical services for which a positive volume-outcome relationship has been documented-that is, patients have better outcomes at higher-volume hospitals. Third, rather than define "high-volume" hospitals as hospitals with the highest 20% of patients, as was done in the California study, we define it in terms of the volume levels used in the empirical studies that have shown better outcomes at higher-volume hospitals. Thus, the number of high-volume hospitals in the New York area varied greatly from service to service (for example, 38 hospitals met the volume threshold for acute myocardial infarction [AMI], while only one hospital was high-volume for gastric cancer surgery and pediatric cardiac surgery). Finally, by studying two different time periods, we can assess the extent to which idiosyncratic factors (e.g., greater awareness of the volume-outcome relationship) might contribute to disparities.

A positive volume-outcome relationship has been documented for a wide array of services, although there is debate about potential explanations (e.g., whether volume results in quality or vice versa, and whether surgeon volume or hospital volume is more important). (For literature reviews, see Halm, Lee, and Chassin 2002; Gandjour, Bannenberg, and Lauterbach 2003.) The robustness of the volume-outcome relationship varies across services. However, in the period covered in this study, volume was identified by the Leapfrog Group and the Agency for Healthcare Research and Quality as a proxy for quality for several surgical procedures and was the basis for some policy decisions in New York state, including the regionalization of AIDS care and coronary bypass surgery.

Methods

Data

This study focuses on residents who lived in the five boroughs of New York City plus the adjacent Nassau and Westchester counties and were hospitalized in that area for any of 17 studied services in the period 1995-1996 (N = 224,533) or 2001-2002 (N = 202,667). Nearly all hospitalizations of residents of these seven counties occur therein, and many hospitalizations of residents of the two suburban counties occur within the city.1 Indeed, in terms of travel time, residents of Westchester have as much or greater access to tertiary hospitals in upper Manhattan than do residents of parts of the city such as Brooklyn or Staten Island. Even so, as a check on our results, we replicated our analysis for several procedures excluding the two suburban counties and found there was no clear pattern of change in our results. Also, out of concern that utilization patterns following events of September 11, 2001, might affect the analysis, we carefully compared utilization patterns in 2001 and 2002. Although a few hospitals experienced a decline in admissions following 9/11, overall utilization patterns for 2001 showed little effect and were quite consistent with patterns in 2002. Our inclusion of data from 1995-1996 provides additional assurance that results were not due to the events of late 2001. (We will primarily discuss the 20012002 results, bringing in the 1995-1996 results only where they shed additional light.)

Patient discharge records from New York's Statewide Planning and Research Cooperative System (SPARCS) are the primary source of data. We included discharges only from short-term general hospitals, excluding Veterans Health Administration hospitals and long-term care units of short-term hospitals. Patients receiving the 17 studied services were identified by International Classification of Diseases, ninth revision (ICD-9-CM) codes in diagnosis and procedure fields (except AIDS, which was defined using the New York state major diagnostic category fields). All patients were age 18 or older (except for pediatric cardiac surgery, which included only patients under 18). The data include clinical information as well as each patient's demographic characteristics, insurance status, and street address or zip code, which were used to measure patients' proximity to high-volume hospitals and, where different, the hospital used. Socioeconomic characteristics of patients at the census tract level were obtained from the U.S. census for 2000.

Services Studied

Although positive volume-outcome relationships had been found for at least 21 hospital services (Dudley et al. 2000; Halm, Lee, and Chassin 2002; Gandjour, Bannenberg, and Lauterbach 2003), we excluded services for which: a) only one hospital provided the service (pediatric cardiac surgery); b) no hospital in the study area met our volume threshold during our study period (surgery for ruptured cerebral aneurysms and for unruptured cerebral aneurysms); and c) prevalence was too low to estimate reliable multivariate models in either of the pairs of years studied (esophageal cancer surgery). The 17 selected services included: five types of cancer surgery (breast, colorectal, gastric, lung, and pancreatic); six cardiovascular services (AMI admissions, coronary artery bypass graft [CABG] surgery, coronary angioplasty, abdominal aortic aneurysm repair, carotid endarterectomy, and pediatric cardiac surgery); three orthopedic procedures (hip fracture repair, total hip replacement, and total knee replacement); two prostate procedures (open and transurethral [TURP] prostatectomy); and admissions for AIDS. Table 1 shows the prevalence of each service during our study periods.

The robustness of the volume-outcome relationship varies among these services. For certain services, including gastric and pancreatic cancer surgery, abdominal aortic aneurysm repair, pediatric cardiac surgery, TURP, and AIDS care, the evidence of the volume-outcome relationship is strong. The evidence is weaker or less consistent for the other services that we studied. We included the whole set for two reasons. First, it is desirable to examine a variety of procedures and conditions since idiosyncrasies may be associated with any particular service. Second, in the period we studied, evidence about the volume-outcome relationship was increasingly available to physicians and patients and thus could have influenced decisions about source of care for any of the services that we included.

Outcome Measure

The dependent variable was whether patients received care from a hospital that met our operational definition of high volume for the specific service for which they were admitted. A hospital was defined as high volume for a particular service if its total annual discharges (averaged for each two-year period) met or exceeded a volume threshold based on the research literature. We used volume standards published by The Leapfrog Group for CABG, coronary angioplasty, abdominal aortic aneurysm repair, carotid endarterectomy, and pancreatic cancer surgery (Birkmeyer and Dudley 2004). For the other services, we used the median volume threshold associated with better outcomes in the literature review by Halm, Lee, and Chassin (2004). The thresholds used are also shown in Table 1.

Explanatory Variables

Patients' race and ethnicity were coded into five mutually exclusive categories from the SPARCS database as follows: Spanish or Hispanic origin (hereafter Hispanic), the non-Hispanic racial categories of white, black, Asian or Pacific Islanders (hereafter Asian), and other. Missing data on patient race and ethnicity (approximately 5.5%) was imputed using a random method …

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Publication information: Article title: Racial and Ethnic Disparities in the Use of High-Volume Hospitals. Contributors: Gray, Bradford H. - Author, Schlesinger, Mark - Author, Siegfried, Shannon Mitchell - Author, Horowitz, Emily - Author. Journal title: Inquiry. Volume: 46. Issue: 3 Publication date: Fall 2009. Page number: 322+. © Not available. COPYRIGHT 2009 Gale Group.

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